Gauge Cluster Question

[NSX_n00b]

Please forgive me if this has been answered. I've done what I think is a fairly exhaustive search of Prime and Google and this answer still eludes me. If it's been answered please link the thread and I'll put my dunce hat on and go sit quietly in the corner :redface:

It's my understanding that any USDM MY Tach and Speedo can be used in any USDM MY Cluster. The change was the PCB but from what I've been told and from what I think I've understood, I should be able to take say the tach and speedo gauge piece (not including the PCB obviously) from a 2002 and put it into the gauge housing of a 91 and it should work (provided I don't over tighten the screws on the back or man handle the needle). If I'm wrong correct me.

My question is, if my above understanding is true, is it also true for the oil/temp gauge and the volt/fuel gauges as well? I haven't been able to find a picture of the backside of either of these gauges so I don't know how they connect and if there are any OBDI vs OBDII implications with them.

 

[Bram]

Yes, all the gauges are compatible across model years, however the lights within the cluster will be different for 97+, due to the fact that these MY came with a security chip built into the key, therefore there is a security light on the cluster. The 02+ gauge faces is blue compared to the previous years in black.

The Volt and Oil gauges are available in Japan @ the NSX Shop

ODB1 vs OBD2 stuff differences are look after within the circuit PCB on the back of the Cluster.

Hope this helps

Bram

 

[drew]

I have the 2002 Update and I have scanned in the section on the cluster and will email it to you; if promise to publish a pin by pin comparison.

We all need to know.

 

[whrdnsx]

from what I understand you can use the Tacho, Speedo, Fuel/Volt from a 2002 to an early cluster but not the OilP/Temp.

For some reason the temp gauge is wound different

 

[NSX_n00b]

Yes, all the gauges are compatible across model years, however the lights within the cluster will be different for 97+, due to the fact that these MY came with a security chip built into the key, therefore there is a security light on the cluster. The 02+ gauge faces is blue compared to the previous years in black.

Bram

@Bram Yes that does help, although whrdnsx seems to contradict this.

I have the 2002 Update and I have scanned in the section on the cluster and will email it to you; if promise to publish a pin by pin comparison.

We all need to know.

I don't think I'm the right guy for a pin by pin comparison, but Johan might be the guy to help?

from what I understand you can use the Tacho, Speedo, Fuel/Volt from a 2002 to an early cluster but not the OilP/Temp.

For some reason the temp gauge is wound different

@whrdnsx I had heard that the oil/temp gauge was different but from a market standpoint not a MY. It was my understanding that a JDM 02+ oil/temp gauge would not work in a USDM cluster but not that there was a change in the USDM 02+ oil/temp operation compared to earlier MY.

Perhaps @Larry Bastanza, @Kaz-kzukNA1 or [MENTION=26435]Old Guy[/MENTION] knows definitively and could help shed some light and clear this up?

 

[Old Guy]

I don't have access to the service manual that covers the 2002+ (in any detail) so I can't compare the test values for the coolant sensor or oil pressure sensor in the pre and 2002+ cars. If the coolant sensor and oil pressure sensor part numbers don't change at 2002 then chances are pre and post gauge mechanisms are interchangeable.

 

[NSX_n00b]

I don't have access to the service manual that covers the 2002+ (in any detail) so I can't compare the test values for the coolant sensor or oil pressure sensor in the pre and 2002+ cars. If the coolant sensor and oil pressure sensor part numbers don't change at 2002 then chances are pre and post gauge mechanisms are interchangeable.

so the plot seems to thicken a bit...


The oil pressure sensor unit is the same part number from 91-05 (37245-PR7-A02) so I'm guessing the oil gauge piece would work. Where it gets interesting is with the coolant temperature sensor.


According to [MENTION=25737]Kaz-kzukNA1[/MENTION] in post #3 of this thread: http://www.nsxprime.com/forum/showthread.php/205064-Coolant-temperature-reading-high
the coolant temperature sender unit is P/N: 37750-PH2-014 and it works for all years. When I look up the Japanese parts diagrams I can find it on the Engine Wire Harness diagram for all MY so Kaz would be right.


However, when I go to the USDM parts diagrams on OEMAcuraParts it says the P/N only fits 91-99. The parts diagram shows the sensor in the picture for 2000 but it doesn't have a number you can click on. The parts diagram however does not show it in the picture for 2001, 2002, 2003, 2004, or 2005 and I can't find the unit anywhere else in the diagrams.


It looks like what changed is the water passage. From 1991-1999 P/N 19410-PR7-A00 and then 2000+ P/N 19410-PBY-A50. However, all JDM MY used the 19410-PR7-A00 P/N.


So now I'm really confused...why only a change in the USDM models? And if Kaz is right, is the coolant temperature sender unit just a different P/N from 2000+ in the US market but it still behaves the same way?

 

[Kaz-kzukNA1]

That's because for Acura late models, ECU is creating the sensor signal for the tempperature gauge.
It does not have the sender unit at the water passage compared to rest of other country spec models.

As I don't have access to later spec USDM ECU, don't know the temperature signal spec created inside the ECU but if you have one, should be able to utilise it fairly easily.
I helped someone a while ago on the same subject as I think he was trying to install JDM NSX-R gauge into his US later model.
I think he managed to make everything working apart from the shift lights so it's possible.

Kaz

 

[NSX_n00b]

That's because for Acura late models, ECU is creating the sensor signal for the tempperature gauge.
It does not have the sender unit at the water passage compared to rest of other country spec models.

As I don't have access to later spec USDM ECU, don't know the temperature signal spec created inside the ECU but if you have one, should be able to utilise it fairly easily.
I helped someone a while ago on the same subject as I think he was trying to install JDM NSX-R gauge into his US later model.
I think he managed to make everything working apart from the shift lights so it's possible.

Kaz

Kaz thank you for the clarification! It’s extremely helpful.

I’m wanting to do the reverse of what you mentioned. I’m wanting to take a 2002 USDM oil/temp gauge and put it into the 1991 cluster. It sounds like what I need to find out is if the internals of the gauge changed to accommodate the signal coming from the ECU or if it will accept the signal from the sender unit as is. Or I’m guessing since the rest of the world models still used the coolant temp sending unit I could just get the JDM blue 2002+ oil/temp sensor and use that as a direct swap.

Thank you again for helping clear up my confusion


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[Old Guy]

Kaz's comments illuminate some of my confusion associated with the 1997-2005 service manual .pdf that I have been looking at. My preference is to work from paper service manuals; but, my 2000 service manual is locked up in the trunk of the NSX in secure storage for the winter, so .pdf it has to be. The 1997-2005 .pdf has missing pages and more importantly doesn't seem to have complete schematics which makes it hard to be definitive about your specific problem (but, somebody scanned and put the document together and posted it for free so I don't complain about free).

From the 1997-2005 service manual, the 1997-1999 models have the 'conventional' type of temperature gauge measurement system with external sender and based upon the test resistance measurements for the sensor in the 1991 SM, looks to be the same from 1991 - 1999. Because the schematic of the guts of the coolant temperature gauge are not available and I have never gutted one I can't be 100% certain; but, my guess is that this is a two coil gauge movement. The changing resistance of the external sensor (at temp goes up and down) alters the split of current between the two coils causing the needle to move. So the gauge is sensing the change in current flow through the external sensor. If I am correct that is a pretty common system.

The 2000+ is where it gets interesting. With Kaz's comments providing guidance, the few pages of the 1997-2005 SM which are available covering the gauge become more clear. The 2000+ coolant gauge no longer has the conventional sensor and the gauge 'sense' wire is connected to the ECU. This does create some uncertainty. The ECU could be outputting a voltage signal to the temperature gauge in which case the temperature gauge has switched from a current sensing gauge to one that just measures a voltage. The ECU could have the output to the gauge just be an (internal) open collector transistor which is operated in pulse width modulation mode to simulate the changing resistance of the old temperature sensor. In this case the temperature gauge would remain a current sensing gauge. I am betting that the gauge remains a current sensing gauge because switching to a voltage sensing gauge would require that the ECU be equipped with a digital to analog converter on that port. The PWM output just requires a simple digital port just like all the ports for injector control, coil control, fuel pump, EGR ..... D/A converters cost more money than a digital port and would be a bit of an oddity in an automotive environment where analog voltage control is definitely not the norm. My bet is that the coolant temperature gauge in the 2000+ remains a current sensing gauge. The test procedures for the 2000+ gauge sort of suggest a current sensing gauge; however, the manual has one test procedure where you disconnect the ECU A connector (contains the sense line for the gauge), turn the ignition on and then measure the voltage between A18 and ground. However, its not clear whether this is between A18 and ground on the ECU side of the connector or between A18 and ground on the harness side of the connector. The SM says to check for approximately 5 volts. If that is on the ECU side, this would screw me up because a digital PWM output normally has no voltage on it unless they are trying to fake an analog voltage output by using an internal pull up resistor. - in which case the gauge is a voltage sensing gauge. All very confusing.

I would bet (easy for me to do when its not my gauge that could potentially be toasted) that the 2000+ gauge remains a current sensing gauge. Visual examination of the gauge assembly to confirm that it is externally identical and retains the same number of connectors as the 1991-1999 gauge would support this. Beyond that, it is pretty much going to be up to testing to confirm. If there are clear terminal markings on the outside of the oil/temp gauge module, you might be able to arrange an external test of the gauge connected to the sensor to see if the needle gives you a 'correct' movement. This would save you the hassle of R&R of the gauge cluster only to find that the gauge is not compatible.

Watching with interest! You must really want the appearance of the 2002 gauge because this is a serious amount of effort to go through.

 

[NSX_n00b]

Visual examination of the gauge assembly to confirm that it is externally identical and retains the same number of connectors as the 1991-1999 gauge would support this. Beyond that, it is pretty much going to be up to testing to confirm. If there are clear terminal markings on the outside of the oil/temp gauge module, you might be able to arrange an external test of the gauge connected to the sensor to see if the needle gives you a 'correct' movement. This would save you the hassle of R&R of the gauge cluster only to find that the gauge is not compatible.

Watching with interest! You must really want the appearance of the 2002 gauge because this is a serious amount of effort to go through.

Well in my mind this was going to be a piece of cake...hahaha whoops.

What’s interesting is the P/N for the gauge assembly changed between 1999 and 2000 so maybe it did go from a current sensing to a voltage sensing gauge? Why would the P/N change unless the internals changed when the external appearance of the gauge didn’t?

I have a USDM 2002+ oil/temp gauge on the way and I’ll order a JDM 2002+ one from Marc and compare the two and report back. My hope is that if the USDM one did change to voltage sensing that at least the JDM one is still a current sensing gauge since USDM is the only market that moved to the ECU sending the signal. If not I’ll have a lot of gauges for sale haha.


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[RYU]

not sure if important but the scaling on the RPM gauge of an Automatic NSX is different - lower redline...

 

[drew]

> I’m wanting to take a 2002 USDM oil/temp gauge and put it into the 1991 cluster.

Purpose? You are going to have a color issue to deal with as well...

>I have a USDM 2002+ oil/temp gauge on the way and I’ll order a JDM 2002+ one

It is reasonable to think that the only difference is that the Oil Pressure is going to be in Freedom Units?

 

[NSX_n00b]

not sure if important but the scaling on the RPM gauge of an Automatic NSX is different - lower redline...

Just for clarity this is all for a 91 MT cluster.

I knew the automatic tach would have the light cut outs for the lights but never even thought about the scaling being different. Good information to have for sure though.


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[Old Guy]

What’s interesting is the P/N for the gauge assembly changed between 1999 and 2000 so maybe it did go from a current sensing to a voltage sensing gauge? Why would the P/N change unless the internals changed when the external appearance of the gauge didn’t?

Are you talking about the part # for a complete cluster assembly? If so, that change might reflect (amongst other things) the fact that the pin assignments on the plugs connecting to the cluster appear to have changed. On the 1991 - 1999 it looks like coolant gauge 'sense' line is coming out on pin B28. The test procedure for the 2000 - 2005 refers to pin A12 on the cluster when checking gauge operation. In early cars the coolant sense line would have fed into the engine wire harness. In the 2000+ cars it would have had to make its way into the ECU harness.

Even though the plug pin count appears to be the same and they may be physically interchangeable, try and plug a complete 2000+ cluster into an early car and I expect you are going to get some surprises.

 

[NSX_n00b]

> I’m wanting to take a 2002 USDM oil/temp gauge and put it into the 1991 cluster.

Purpose? You are going to have a color issue to deal with as well...

>I have a USDM 2002+ oil/temp gauge on the way and I’ll order a JDM 2002+ one

It is reasonable to think that the only difference is that the Oil Pressure is going to be in Freedom Units?

The purpose is to try and do the entire cluster with the blue faced gauges.

I actually don't know what the JDM oil pressure gauge will be in, the gauge on my USDM 91 is in kg/cm squared and the gauge on the USDM 02+ is in 100*kPa which is almost a 1:1 conversion. I'm guessing the JDM will probably be in 1 of those 2 measurements. I guess I'll find out.

Are you talking about the part # for a complete cluster assembly? If so, that change might reflect (amongst other things) the fact that the pin assignments on the plugs connecting to the cluster appear to have changed. On the 1991 - 1999 it looks like coolant gauge 'sense' line is coming out on pin B28. The test procedure for the 2000 - 2005 refers to pin A12 on the cluster when checking gauge operation. In early cars the coolant sense line would have fed into the engine wire harness. In the 2000+ cars it would have had to make its way into the ECU harness.

Even though the plug pin count appears to be the same and they may be physically interchangeable, try and plug a complete 2000+ cluster into an early car and I expect you are going to get some surprises.

I'm talking about the P/N for just the Oil/Temp gauge assembly. For a 1999 it is P/N: 78150-SL0-J01 but for a 2000 it is P/N: 78150-SL0-A02. The P/N's for the Speedo/Trip and the P/N's for the Fuel/Volt gauges stayed the same between the 2 years. The Tach/Odometer P/N's do differ between 99 and 00 though.

My plan based on the feedback I have gotten and from what I've read from other threads is that I should be able to take the Fuel/Volt gauge assembly from my '91 out and put in the one from the 02+ with no issues. I should be able to take the gauge piece ONLY (face/needle and not the PCB) of both the Tach and Speedo from the 02+ and attach them to the '91 PCB's and not have an issue. And then I might be able to do a direct swap of the 02+ US Oil/Temp gauge assembly but if the internals changed it from a current based to a voltage based gauge then I should be able to swap in the JDM 02+ Oil/Temp gauge assembly since it still gets its signal from the sender unit and not the ECU like the USDM one.

 

[drew]

>My plan based on the feedback I have gotten and from what I've read from other threads is that I should be able to take the Fuel/Volt gauge assembly from my '91 out and put in the one from the 02+ with no issues.

Any update on this?

 

[NSX_n00b]

>My plan based on the feedback I have gotten and from what I've read from other threads is that I should be able to take the Fuel/Volt gauge assembly from my '91 out and put in the one from the 02+ with no issues.

Any update on this?

Unfortunately not. Still waiting on the 02+ Tach and JDM 02+ oil/temp gauge to show up


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[james0933]

Any update to this?

 

[NSX_n00b]

Any update to this?

I thought I had provided an update but I'm wondering if I just replied to drew directly. I'm still waiting on the JDM 02+ Oil/Temp gauge to do this myself but I know that the 02+ Fuel/Volt and JDM 02+ Oil/Temp will definitely work in a '97-'01 USDM NSX cluster. I know an owner that has them and they are working properly. So I'm hopeful that the setup will work in the '91-'96 MY.