LOST IGNITION FROM USING A BATTERY DISCONNECT?

[TANTO]

Hey Brothers. Had my 92 coupe since 93 cold dead hands car. While the ignition and the radio were on I stupidly touched the two subwoofer spkr wires together. I hear a pop in the dash and then a split second later another smaller pop. No burnt wire smell, lost dash lights and of course radio. All else seemed fine and I was planning on pulling the audio system anyway. All fuses were strangely still good. Now another issue comes up and is the heart of my plea for help. A few days I’m starting to look at those dash lights and I lose all ignition. Odyssey batt is 100%. So I’m puzzling over this and see In the elect FSM a warning ”do not crank w/grd cable removed or you will severely damage the wiring”. wtf? I do have a discon switch in my neg frame ground to stop parasitic loss. I do remember one day cranking the key for split second just to see where I was and likely had the batt switched out. In all my years I must have cranked before with that ground switched out without damage, but perhaps this time it took out my ignition(?). As an ex-wrencher I do have the skills to pull the dash and repair wires, but I don’t yet know what I’m looking for. I realize I likely have two issues here, but any help greatly appreciated. Thank you Steve Glover for your great article in NSX DRIVER issue 3 2022

 

[Old Guy]

The wording in the ETM is:

Do not attempt to crank the engine with
the ground cable disconnected or you will
severely damage the wiring.

Although not explicitly stated, I expect the reference is to the ground cable that connects the engine block to the back of the firewall. If you engage the starter motor with that ground cable disconnected the starter current will seek out alternate paths back to the chassis ground which may not be rated for the typically 100 amp starter current resulting in melting of those connections.

If you have a disconnect switch in the ground connection for the battery there is no way that you can operate the starter motor with that switch in the open position unless you have got creative with modifying the vehicle wiring or you were attempting a start from an external jump pack / battery in which case the ground on the internal vehicle battery does not enter into the circuit.

If this is the factory subwoofer the two speaker wires are internal to the enclosure and not accessible unless the enclosure has been taken apart so you would need to be more specific about which two wire you shorted. On the OEM factory subwoofer, power comes into the enclosure on the orange (+) and black (ground) wires. The sub and the door amps are powered up through the power amplifier relay which gets power through fuse #51 (un switched power). Fuse #51 and the amp relay are on a completely different circuit from the head unit. As a result, even if you damage the amplifier power supply the head unit should continue to function. Of course, this assumes that you still have the factory audio system. If you have an aftermarket audio system then you are n your own to try and figure out how it has been wired up.

When you state that you lost dash lights, are you talking about the dash warning lights that normally come on when you turn the ignition to the 'run' position? Also, you state

A few days I’m starting to look at those dash lights and I lose all ignition.

Lose all ignition is not very specific. Does this also mean that the starter motor will not engage? If so, and particularly if your 1992 still has its original ignition switch I would be inclined to leap frog a number of trouble shooting steps and check the operation of the ignition switch. With the switch removed for testing, you can also measure voltages on the vehicle harness side of the connection plug to make sure that the power supply to the ignition switch is OK.

If the disconnect switch in your battery ground connection is one of those battery post mounted switches, they do not have a good reputation in terms of reliability. Check the switch to make sure that it has not flaked out on you. When I put my car into storage for the winter, I just disconnect the ground cable clamp on the battery - post.

 

[TANTO]

The “disconnect” switch I use is from Jegs for use on the power side that NHRA requires for emergencies. I use it on the battery ground to body as I have long periods of no driving and it saves me batteries. That ground circuit is fine and I do have power to the underhood fuse box. Thanks for your interpretation of the service manual warning. Regarding the initial audio mess up, I did cross the orange and black wires feeding the sub amp. I immediately lost the radio head unit, clock and the dash lights that light with the headlights. Not sure about the clock. But I did have all startup lights and cranking and most systems seemed normal. Sorry for the data creep, but perhaps I should mention that I was installing LED taillights around the time I lost additional items. I suspect trying to figure out what I did to get here is likely not relevant now with so many variables and my questionable memory. I assume it’s all diagnostics now. So here are my current conditions. WHAT IS WORKING: the light ring around the ignition, have the normal red battery light at the top left of the dash with key on, have AC lights, have headlights, have horn. I DON’T HAVE: clock power, no dash lights under any condition(except the red bat), no cranking, no clicking. Only 25k on the car, all garaged, no elect parts added except V1 radar. I have taken out the audio system fuses. FWIW my gut says that with these low miles, I somehow messed up something in a control circuit although I’m assuming that I should fully go thru the power circuit first(?) Despite my current member status, I was a member of the original big list and fully realize how valuable this community is! TIA

 

[Old Guy]

If you shorted the black and orange wires at the sub woofer connector, you should have blown fuse #51 (20 amp). This will kill all audio output. According to the vehicle wiring diagram, fuse #51 only supplies the power amplifier relay and the audio amplifiers. Blowing fuse #51 should not affect anything else. You said in your first post 'all fuses good'. Go back and check fuse #51 to determine whether it is blown or not blown. If it is not blown, that is a significant problem since it indicates wiring damage elsewhere in the vehicle. The first place to start would be the power amplifier relay in under hood relay box B. Remove the relay which will allow you to check the operation of the relay (as per service manual). Have a look inside the relay box at the plug that the relay fits into. Are there any signs of burnt or melted plastic? From the socket terminals you can test to make sure that you are getting power from fuse #51 and check continuity from the relay to the orange wire that supplies the sub woofer.

The dash lights are on a completely separate circuit from the amplifier relay circuit and should be unaffected by problems on that circuit so you may have multiple separate problems.

The starter motor system is pretty much separate from the rest of the vehicle wiring system. If you cannot crank the engine (starter motor) that can be caused by the following:
- the ignition switch has failed
- bad battery post connections
- the starter motor has failed
- the clutch interlock switch has failed or the little plastic button that operates the switch has dropped out
- the starter cut relay has failed
- the security system has failed

The only dash light that really matters for this problem is the ECU CEL light. When you turn the ignition switch to run that light should illuminate for a couple of seconds and then go out. That is the ECUs Power On Self Test function (POST). If the CEL does not illuminate for the POST test AND you do not hear the main EFI relay clicking AND the starter motor does not crank, first confirm that the battery post connections are good because that is a common NSX problem and it is easy to do,; but, the most likely failure is the ignition switch. Other things can cause these symptoms; but, the ignition switch is the place to start.

The ignition switch has two fused circuits supplied by fuse #29 (circuit A) and fuse #9 and #12 (circuit B). Failure of these fuses will cause problems; but, I assumed you confirmed that those fuses are OK when you said all fuses were still good.

 

[TANTO]

I will show my disconnect to possibly make this thread useful for others who let their cars sit a lot. This switch is a mostly plastic switch that was once used by NHRA folks. Jegs not longer offers this switch in favor of more robust all metal switches which i do have on my mini-van. I'm a light weight nut so i tried this switch which has worked for over 20 years FWIW. I noticed that MITA offers a $300 dollar variant kit. Don't know whether the mita switch is on the negative or the positive side. Old Guy can comment of this if desired. The NHRA switches are desinged for use on the positive side. I'm a semi-electrical guy. Please understand that my personal issues have nothing to do with this disconnect, but since my post may come up on searches, i felt i should clarify. Thank you Old Guy for your excellent post which will guide me to a resolution. I have ordered a new ign switch and cut relays as i should have these while available. I will test the ign switch before in install the new. The audio fuse #51 may well have been blown initially, it was last winter so i'm not clear. I'm shocked that no other fuses are blown, but with the helpful post i'm confident i will get this resolved. Will follow up. Thank you Old Guy! I'm 71 but not so sharp as you.

 

[TANTO]

So i'm still stuck a bit. The ignition switch DID fail testing, so i replaced it (thank you mita!). The car will now crank! The starter relay did pass tests. The clutch interlock tested good also, but i removed/bypassed it anyway along with the cruise switch also as i removed the cruise long ago. I have not gotten into the security system, but i assume it's fine if it cranks. I believe i'm getting all the normal start up dash lights, but i am not getting the dash gage surround lights and the clock light. AC is fine. I pulled and tested every single fuse again. My major concern now is that with the key on I'm getting a constant humming sound coming from the radio(removed) area. As it doesn't stop i assume it's not the fuel pump pegging. I guess i'll pull the console and try to pinpoint the hum. And then try to see if power is getting to the dash and clock, and perhaps remove them and bench test(?). Any thoughts greatly appreciated. Again thanks for your patience and help.

 

[Old Guy]

I am not completely clear about your current status. I understand that the engine will now crank; but, I am reading between the lines that the engine does not start, or is the only remaining problem that you seem to be missing some dash lights and you have a strange hum?

If the engine will not start, is the fuel pump going through its prime cycle (on for a couple of seconds and then turns off) when you switch the key to run; but, do not switch the key to start? If the fuel pump is not priming then the ECU is not powering up which could be the main EFI relay (and a few other things).

I am not exactly sure what you mean by dash surround lights. If that is the back ground lighting for the instrument cluster, that does not normally light up unless you have the position or headlights switched on.

Can't comment on the hum.

 

[Scrapdog2grand]

So i'm still stuck a bit. The ignition switch DID fail testing, so i replaced it (thank you mita!). The car will now crank! The starter relay did pass tests. The clutch interlock tested good also, but i removed/bypassed it anyway along with the cruise switch also as i removed the cruise long ago. I have not gotten into the security system, but i assume it's fine if it cranks. I believe i'm getting all the normal start up dash lights, but i am not getting the dash gage surround lights and the clock light. AC is fine. I pulled and tested every single fuse again. My major concern now is that with the key on I'm getting a constant humming sound coming from the radio(removed) area. As it doesn't stop i assume it's not the fuel pump pegging. I guess i'll pull the console and try to pinpoint the hum. And then try to see if power is getting to the dash and clock, and perhaps remove them and bench test(?). Any thoughts greatly appreciated. Again thanks for your patience and help.

Like Old guy said.


You have most likely blown 7.5 fuse 33 in the relay box, possibly others.
The hum is probably the aspirator fan motor.

 

[TANTO]

The new ignition switch got the car running fine now, but still have no instrument background lights(with the headlights on) and no clock. One of the leads to the clock is hot. ALL fuses triple checked. I'm not done staring at the electrical diag's, but it looks like both items are fried from simply crossing the sub amp inputs. I know, I know, it seems crazy hard to believe, but i'm living it. I'm pulling the dash now to see if i can find any burned up bulbs or to ship to Mita for a rebuild. The instrument panel is $5600! The hum was the AC sensor. That little fan is pretty loud. Thanks guys and Happy Holidays!

 

[Heineken]

The AC sensor should be barely audible - but that's something you can focus on after the major items are fixed.
If possible, treat the clock and the cluster illumination separately.

Starting with the clock might be easier than pulling the cluster especially since the clock has much less wires going. Use the electric manual to identify the wires to the clock - there should be permanent, ignition and headlight switched power. If these are OK, check the resistance from the ground wire to chassis ground.

It's easy to loose concentration when so many issues happen at once but try to keep a cool head and fix it item by item

 

[TANTO]

Need to close out this tread as the Old Guy put the disconnect issue to bed in his first reply. I had a bad ignition switch. Still working on some lighting issues which i may ask for help again in another thread. Thanks to Old Guy for your EE skills and Heineken for his needed calming words.

 

[Heineken]

Thanks for wrapping it up so far - hopefully you'll get those last gremlins sorted out soon.

 

[Old Guy]

Probably need to add ignition switch replacement / rehabilitation on to the replace your main EFI relay, replace the capacitors in your CCU, replace the capacitors in your stereo, replace capacitors and recalibrate your instrument cluster, replace coolant hoses, replace ............. list.

 

[Bonneville Don]

Hey Brothers. Had my 92 coupe since 93 cold dead hands car. While the ignition and the radio were on I stupidly touched the two subwoofer spkr wires together. I hear a pop in the dash and then a split second later another smaller pop. No burnt wire smell, lost dash lights and of course radio. All else seemed fine and I was planning on pulling the audio system anyway. All fuses were strangely still good. Now another issue comes up and is the heart of my plea for help. A few days I’m starting to look at those dash lights and I lose all ignition. Odyssey batt is 100%. So I’m puzzling over this and see In the elect FSM a warning ”do not crank w/grd cable removed or you will severely damage the wiring”. wtf? I do have a discon switch in my neg frame ground to stop parasitic loss. I do remember one day cranking the key for split second just to see where I was and likely had the batt switched out. In all my years I must have cranked before with that ground switched out without damage, but perhaps this time it took out my ignition(?). As an ex-wrencher I do have the skills to pull the dash and repair wires, but I don’t yet know what I’m looking for. I realize I likely have two issues here, but any help greatly appreciated. Thank you Steve Glover for your great article in NSX DRIVER issue 3 2022

I have a 1991 NSX and I had a former NSX tech in the Orlando area replace the clutch. Soon afterward, I started having electrical problems. SRS, and other lights on the dash. If I shut the car off, and restarted they would go away. But they would return. After doing a restart at a stop light, the car would not engage the starter motor.
After reading some threads (you guys rock!) I thought I had a bad ignitions switch so I replaced it with an OEM part. BEFORE I tried to start it, I re-read this thread and found the second posting that warned about severe consequences for trying to start without the engine ground strap to the firewall secure so I decided to check. IT WAS NOT CONNECTED AT ALL.

I connected it to the longer bold on the hydraulic clutch which looked like the only place the wire would reach. The car still won't engage the starter motor. When I turn the key, I get all the usual lights and I believe everything else is right.

I am open to any help I can get. I tried the Acura Dealer in Sanford and the phone director person didn't know if they have a certified NSX tech. I left a message for the Service Manage and can't even get a call back. Does anyone know of a qualified tech near Orlando?
Thanks for all you do. You are a tremendous help to me.
Bonneville Don

 

[Old Guy]

There are two engine grounds. One on the right front head cover

The other is on the middle / left side of the engine compartment and connects to the transmission housing. This diagram of the transmission shows the transmission ground cable. You need to look at the diagram really closely to see the actual cable - it is definitely not the clutch slave cylinder mounting bolts.



Based upon the diagram, I am thinking that you might need to loosen or remove the air box and the control box to get eyes on the ground strap mounting point - I will defer to somebody who has actually had to do this. I am thinking that your "former NSX tech in the Orlando area" had an oops moment and missed reconnection of the ground cable during the clutch replacement. I leave it to you as to whether you want to take up the error with the former tech.

Have a look at the second ground strap at the right front of the head. My car is in storage so I can't check it; but, my fuzzy memory is that it is a smaller strap and may not be rated for the starter motor current which can approach 100 amps. Check the complete length to see whether it has been damaged by overheating. Heat damage will be most likely at the crimped terminals on either end. When you crank the starter motor with the main ground strap disconnected the starter current flows through the smaller ground strap which can cause a significant voltage drop between the engine block and the rest of the car resulting is erratic operation - as you seem to have discovered.

I did a clutch hydraulic system flush last year. I did not pay a lot of attention to the mounting bolts for the slave; but, my fuzzy recollection is that they are not big bolts (M5 - M6???). If that is the case I would not use them as a temporary grounding point. If the bolts are in fact larger diameter and the ground lug does not flop around on the bolt, then they may suffice as a temporary ground strap mounting point.

The starter motor circuit is pretty simple


Battery to ignition switch to starter cut relay to the starter motor solenoid. Once you get the engine ground cable sorted out and presuming the cables back to the battery are OK (the battery post cable clamps and the battery ground cable are common failure candidates) the likely problem candidates are
- the ignition switch - which you should have eliminated
- the starter cut relay which includes the security system and the clutch interlock switch (I assume you have checked to confirm that the clutch switch stopper has not dropped out)
- the actual starter motor

After the ground cable problem has been fixed, the fastest way to isolate the problem area is a jump test on the starter motor.
- get about 1m of #14 wire with about 1cm of insulation stripped from each end for use as a jumper.
- remove the blk/wht starter wire from the starter motor solenoid
- make sure that everything is clear of moving stuff on the engine because the next step should cause the engine to start turning. Make sure the key is not in the ignition switch because the engine can start if the key is switched to run.
- carefully hold one end of jumper wire on the jump start terminal in the engine relay box and then touch the other end to the terminal on the starter solenoid. This should cause the starter motor to engage and turn the engine over.

This test by-passes everything in the starting system control circuit. If the primary (big cables) connections are OK then you likely have a starter motor problem if the motor does not operate. If that is the case, chances are that the bad ground connection may have resulted in a low pull in current on the solenoid leading to burned contacts on the solenoid. After removal of the starter motor it may be possible to clean up the contacts with a file or there are contact replacement kits available for less than $20. If you search on Prime there is a thread from about 5-10 years ago describing replacement of the starter solenoid contacts. You may also be able to find a local electrical specialist who will rebuild it for you. Remans are available; but, the quality can be dodgy.

If the starter motor operates that pretty much narrows it down to a bad electrical connection somewhere in the starter circuit or a problem with the starter cut relay circuit which is a headache that likely requires a completely separate thread .

 

[Bonneville Don]

Wow. Thank you so much. I will try all of this and report back.

 

[Bonneville Don]

Wow. Thank you so much. I will try all of this and report back.

I can't thank you enough for your detailed, step by step process to diagnose this. I am far from an accomplished auto-electric guy and your attachments were a big help. I have an electronic version of the repair manual but find it difficult to navigate. Here is where I'm at now;

1. I confirmed that the grounding strap on the front engine cover was in place and showed no signs of overheating.
2. I ended up removing the air box to get to the main grounding strap and found that it was NOT CONNECTED at all. The hole in the cable end was smaller than I would have expected but fit a 6M bolt. There was only one choice to place it based on the length of the cable (OEM I think) which was on a 1/4" thick bracket bolted to the top of the transmission that appears to be used for lifting the engine/trans with a chain. It had a 6M hole in it with no bolt so I attached the ground wire there. I think it is correct.
3. I used my remoter engine starter (plunger style wire for jumping solenoids) from the jump start terminal in the engine relay box to the starter motor black/white prong as you suggested. The starter motor worked fine. I then inserted the key and turned to the on position and used the remote starter to start the engine. Worked fine.
4. With the black/white wire returned to the starter, I tried the key to start and it still does not work. When the key is turned, all the dash lights come on as normal, and I had the interior fan on low. When I turned to the start position, everything goes off including the fan. I assume this means that I still have an open connection somewhere in the ground circuit?
5. I looked at the clutch safety switch under the dash and it looks o.k. to me. The black plunger is in intact and seems to operate fine. I don't know where the "starter cut relay" is located.

When this event happened, I did a very rapid shut off of the key switch, and then a rapid restart try. I may have heard a "pop" but I can't be sure. I was at a stop sign with traffic behind me.

If you know of a thread discussing how to diagnose from here, I would appreciate helping me get there. Or, if you have time, I would greatly appreciate your recommended next steps.
Once again, I can't tell how much I appreciate your guidance and wisdom. I'd be more than happy to pay you for your time or if anyone knows a competent NSX tech in Orlando area, a reference.
Thanks much,
Bonneville Don (that's another story)

 

[Bonneville Don]

1. I confirmed that the grounding strap on the front engine cover was in place and showed no signs of overheating.
2. I ended up removing the air box to get to the main grounding strap and found that it was NOT CONNECTED at all. The hole in the cable end was smaller than I would have expected but fit a 6M bolt. There was only one choice to place it based on the length of the cable (OEM I think) which was on a 1/4" thick bracket bolted to the top of the transmission that appears to be used for lifting the engine/trans with a chain. It had a 6M hole in it with no bolt so I attached the ground wire there. I think it is correct.
3. I used my remoter engine starter (plunger style wire for jumping solenoids) from the jump start terminal in the engine relay box to the starter motor black/white prong as you suggested. The starter motor worked fine. I then inserted the key and turned to the on position and used the remote starter to start the engine. Worked fine.
4. With the black/white wire returned to the starter, I tried the key to start and it still does not work. When the key is turned, all the dash lights come on as normal, and I had the interior fan on low. When I turned to the start position, everything goes off including the fan. I assume this means that I still have an open connection somewhere in the ground circuit?
5. I looked at the clutch safety switch under the dash and it looks o.k. to me. The black plunger is in intact and seems to operate fine. I don't know where the "starter cut relay" is located.

When this event happened, I did a very rapid shut off of the key switch, and then a rapid restart try. I may have heard a "pop" but I can't be sure. I was at a stop sign with traffic behind me.

If you know of a thread discussing how to diagnose from here, I would appreciate helping me get there. Or, if you have time, I would greatly appreciate your recommended next steps.
Once again, I can't tell how much I appreciate your guidance and wisdom. I'd be more than happy to pay you for your time or if anyone knows a competent NSX tech in Orlando area, a reference.
Thanks much,
Bonneville Don (that's another story)

 

[Bonneville Don]

I re-read some of the other threads and decided to defeat the clutch cut off switch with a paper clip. IT WORKED!
So in the end, it was the main ground strap not connected at the transmission, AND the clutch cut out switch.
I will order a new switch and then follow instructions in the other thread on replacing it. Looks like a real hard repair as you really need to stuff yourself under the dash.
Thanks again for the help!

 

[Old Guy]

Its good that the problem is just the switch and not the starter cut relay or the security system. The upper clutch interlock switch is a definite treat to work on. In addition to removing the lower cover in the footwell it may help to remove the knee bolster / lower dash pad. I don't think this will make it easy to access the switch; but, I think it will make it easier to see what you are doing.

The knee bolster is a pain to get off because it is hard to get a grip on it. To make removal easier, pull the steering wheel all the way back and then raise it. This makes a larger gap between the left side of the steering column cover and the left portion of the bolster pad. As long as you don't have Andre the Giant hands, you should be able to get your fingers into that gap which will allow you to get a much better grip on the bolster pad. Pull the pad straight back towards you and it should release - does take a little force. Straight back is important. If you pull up or down you risk braking mounting tabs. Once you have completely released the pad on the left side if you gently lever the loose side of the pad back a bit you will create a larger gap between the pad and the right side of the steering column and you can fit your fingers in there to repeat the process on the right side.

What you want to avoid is pulling back so hard on the left side that all the retainers release at once resulting in the pad bending and snapping in the center.

 

[Bonneville Don]

Its good that the problem is just the switch and not the starter cut relay or the security system. The upper clutch interlock switch is a definite treat to work on. In addition to removing the lower cover in the footwell it may help to remove the knee bolster / lower dash pad. I don't think this will make it easy to access the switch; but, I think it will make it easier to see what you are doing.

The knee bolster is a pain to get off because it is hard to get a grip on it. To make removal easier, pull the steering wheel all the way back and then raise it. This makes a larger gap between the left side of the steering column cover and the left portion of the bolster pad. As long as you don't have Andre the Giant hands, you should be able to get your fingers into that gap which will allow you to get a much better grip on the bolster pad. Pull the pad straight back towards you and it should release - does take a little force. Straight back is important. If you pull up or down you risk braking mounting tabs. Once you have completely released the pad on the left side if you gently lever the loose side of the pad back a bit you will create a larger gap between the pad and the right side of the steering column and you can fit your fingers in there to repeat the process on the right side.

What you want to avoid is pulling back so hard on the left side that all the retainers release at once resulting in the pad bending and snapping in the center.

I just received my new clutch cut out switch and installed it. I had to adjust the depth of it a little to get it to work. At first, the engine turned over fine, but would not start. After several attempts, it did start but did not run smoothly. After restarting a couple times, it seems normal again. Perhaps sitting for a couple months was the problem?

I also found a small, rubber, cylindrical boot laying in the footwell. It is 1 1/4" long and 1/2" wide. I don't see where to return it to? Any help would be appreciated.

I can't thank you enough for your help. I called my Orlando Acura dealer and they didn't know if they had a certified NSX tech on staff. I asked for the Service Manage to give me a call. Still waiting.
THANK YOU for your help!