SRS - status light stays illuminated

C

CharginRAM

New Member
Joined
7 June 2018
Messages
5
Hi folks!

I’m currently performing FI on my SRS system. The SRS light stays ON - constantly, after startup. I have the workshop manual for my ‘91, and it refers to a test harness.(07MAZ-SL00500). By using this harness, and following the matrix contained in the manual, finding the faulty component is suppose to be easy.... ;) I have already contacted Honda about borrowing one. («Shockingly», they cannot supply them). Is there anyone who might supply with the info showing the SRS unit receptacle clocking/orientation, versus the test harness clocking?
 
(trying again after my phone decided to delete the entry)

The harness is still available at your local, but online, OEM parts supplier for about $60.

However, check the SRS fuse on the front LH side of the interior, it is probably blown.

If blown, it means your SRS needs to be rebuilt...the caps have gone and took a leak all over the board.
 
CharginRAM said:
I have already contacted Honda about borrowing one. («Shockingly», they cannot supply them). Is there anyone who might supply with the info showing the SRS unit receptacle clocking/orientation, versus the test harness clocking?
Click to expand...
I've had a number of SRS light issues over the years which were more than just a fuse replacement. If the A/C evaporator (in the dash) drain gets blocked, you can have water spilling into the passenger footwell and the first time it happened, I fixed the drain; dried things out; and the light went out. The second time, that didn't work so I ended up borrowing a harness from my local dealer as I was on good terms with the mechanic there who does most of my common maintenance. I had already paid them to use it and the matrix results were that there was a wiring problem and I think he really didn't want to pursue it beyond that so may have taken pity on me. I ended up replacing the entire SRS wiring under the carpet (no fun) and that did not fix it. I ended up sending my unit to BrianK here on Prime who replaced the caps for a reasonable cost and that fixed my problem. Unfortunately, given the location of the SRS module (under the console), there's really no way of easily testing any of the connections without using the harness. Even just removing the module is a pita because the screws holding it in have some kind of threadlocker on them and your best bet is to apply a soldering iron to them to release it otherwise you'll end up stripping the screws. You might want to remove it first .. open it up .. and if some capacitors are leaking, just send it to Brian to be fixed. The capacitor issue is well known and shows up in the stereo amps and the head unit as well.
...Ian
 
Hi guys, many thanks for the inputs. I am currently away for work. The fuse seems like a good place to start. I also know of the moisture problem (A/C system). I did remove the SRS unit a few weeks back and performed a quick exteriorwise insp. All seemed good. So if not the fuse, I shall open it up and inspect the caps. Again, many thanks! I shall keep you guys updated :)
 
Hi folks!

Just a little update here...

So I finally got some time to get lost in the world of fault isolation... after receiving the test harness 07MAZ-SL00500 I started measuring DC levels, just as described in the workshop manual. As mentioned here, earlier in a post, I was quickly led to the main fuse, which had melted away. It got replaced, and as expected it blew off pretty quickly. Since I don't have time to wait for a new harness, I decided to open the SRS unit itself and take a look for blown caps. (again mentioned as a probable cause - by this fantastic forum). The attached picture pretty much sums it up...

Just for future info, for people starting out with the same issue... use the drawing as reference, and measure directly on the SRS unit itself. (JUST MAKE SURE YOU USE A SOCKET SMALL ENOUGH/FIRM, TO PREVENT SHORTING THE PINS ;) ).The DC levels matrix is also attached in the 3rd picture. This matrix is the first step, in any case of "SRS light stays ON constantly"

Again, many thanks guys! Now I need to decide if I'm up to the task... ;)

Matrix.jpgPlug.Recept..jpgCap.Leak.jpg
 
Hi guys!

Just a short update...

Finally got some time to get lost in the world of fault isolation. Just received the test harness (07MAZ-SL00500) and started measuring the DC levels, just as described in the workshop manual matrix. The matrix led me to the SRS unit main fuse, which has melted away. Thanks to this wonderful forum I decided to open up the unit itself (SRS control unit), and have a look. After a brief period gazing at the circuit board I spotted a small leak at one of the caps'.

I attached three pictures that might aid others with the same "frustrating" problem ;) Now, just bypass the test harness and measure directly on the unit receptacle. Just be sure not to short any pins with a clunky probe, preferably a small socket to push over.

Many thanks for the reply guys... now I need to decide if I'm up for the task of changing the caps... ;)

Matrix.jpgPlug.Recept..jpgCap.Leak.jpg
 
That leaking C24 is the same capacitor that was leaking on the SRS control unit that crxguy52 was dealing with. I recall that in his case both C23 and C24 were leaking. Removal of the capacitors is not that difficult. Removal is a bit fussy with solder wick and a soldering iron; but, pretty easy if you have access to a de soldering station. If you go the de soldering wick route, get fresh wick from an electronics vendor. De soldering wick is impregnated with flux which tends to disappear on wick stored on a shelf and left exposed to air, leaving it relatively useless when it comes to removing solder. The bigger choice is whether you replace the other small capacitors and whether this extends to include C15 (the biggy).

Crxguy52 also identified an issue with a failed transistor. You might want to PM him to see if he resolved that problem.
 
Hi guys!

Another update regarding the SRS light F.I. Unfortunately, the bulb still stays lit.
After disassembling the control unit itself, I removed the two leaking capacitors and cleaned the affected (and adjacent area) carefully using q-tips and isopropanol.
(The broken units were C23 and C24, respectively). So after cleaning I installed a new pair, to the same specifications. Happy and joyful, thinking “wow, that did the trick”, I went ahead and reconnected it to the car. Turning on the ignition key…. Fuse blows again, and light shines brightly as ever!

Now it really starts to be a pain in the ass! It seems (from the attached pictures that the old electrolyte was able to dissolve some of the old “top layer”. I went to school and learned very basic stuff about this, but I never worked in a component shop (with all of the neat knowledge and experience that follows). Seeing the “electrolyte damage” I kinda had a bad feeling; that the repair wouldn’t’ work flawlessly. Anyways, I thought that the damage at hand would result in cutting the circuit board lines – rather than shorting it. So it must be another faulty component then? “CRXGUY52 did some silicone, re-solder repair stuff to his board. As of right now I don’t have all that stuff available. By experience I also know what poking around with old shit (over-cleaning may do more damage that good.) One last thing; the adjacent transistor does not show any exterior sign of damage, atleast.
IMG_2900.jpgIMG_2896.jpg
 
My SRS light was constantly illuminated as well. The fuse was blown and after getting the SRS unit out, I found the capacitors leaking very severely and the circuit board was fried. I actually have a 1/4" charred hole in the board. I've been replacing bad capacitors for over 40 years now. I worked for Tektronix for 10 years and ABC Television in Hollywood for 28. I have certainly replaced thousands over the years. My advice is to replace ALL of the capacitors with Panasonic FC series. They are available online at Digi-Key. C15 (the large cap) is the backup power for the unit and I doubt that needs to be replaced but you may want to anyway.
 
Hi Craig,
I hope you are well and enjoying your NC. I am looking at your old NA1 here, still for sale at DCH Tustin Acura. Do you foresee any major maintenance or repair problems coming up? If so would you mind sharing with me? Just trying to make sure I wont end up with a big repair bill as soon as I drive off the lot. Thanks so much.
Henry
 

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