Question about A/C Panel Lights - Not coming on as normal

[jawn101]

So I'm baffled by this. Up until today, my A/C panel lights worked as designed - always on with the key, regardless of the status of the LMS. I jumpered out the rheostat long ago because I have all LED panel lighting, which is why I like the original design rather than the "on with LMS only" style.

Today, the A/C panel lights don't come on at all. If I remove the relay and jump it out per the mod at http://www.dmcnews.com/Techsection/acpanellites.htm (basically connecting the A/C panel lights directly to ground) they work perfectly when I turn on the headlights.

I tried swapping in a different relay and it didn't help. The schematic is very hard to understand in this situation because there are tons of light green and red/orange wires that just vanish into huge bundles of light-related goodness.

I pulled out the red resistor and verified that it's not burned out, and that it reads as a resistor - not quite sure what it does, frankly. I do know that I tapped into one of the pins on it for key-on signal for Dave M's solid state dome light timer.

Does anyone have any idea what could be going on here?

[DMC5180]

Do your Windows move up/down. If not, check fuse 11

That's the supply feed for A/C panel too.

Remove the A/C panel relay and probe terminals 87 and 87a. You should see voltage on both. 87a (center) LG/W should be battery voltage. 87 will be reduced voltage from the resistor.

The resistor was used to drop the light level for night time illumination.

When the headlights are off in Daylight. The panel is at full brightness for daylight conditions.


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[jawn101]

Yes, windows work fine. If the fuse was shot I imagine the jumper in the relay socket wouldn't work, right?

[jawn101]

And when you say probe 87 and 87a, do you recommend the probe go to the ground pin in the relay or straight to the battery, or...?

[DMC5180]

Yes, windows work fine. If the fuse was shot I imagine the jumper in the relay socket wouldn't work, right?

No, when you jumper, you are using the 12v power that would normally just energize the relay coil. That feed comes from the headlight switch (R/O) wires. It's a separate circuit.

It does confirm the wire Circuit from the Relay relay to the panel is GOOD.

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[DMC5180]

And when you say probe 87 and 87a, do you recommend the probe go to the ground pin in the relay or straight to the battery, or...?

If you are using a 12v test light, connect the alligator clamp to Ground. Probe the Relay socket for Power.

Also make sure the thermals all appear to be seated in the top of the socket.


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[jawn101]

If you are using a 12v test light, connect the alligator clamp to Ground. Probe the Relay socket for Power.

Also make sure the thermals all appear to be seated in the top of the socket.


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What do you mean by all thermals? The thermal trip breakers? What about seating them?

[DMC5180]

Socket terminals, make sure none have been pushed down.


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[jawn101]

Socket terminals, make sure none have been pushed down.


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Oh, I gotcha. That was the first thing I checked - I did find that my (PO installed...) starter relay TSB mod used a terminal with no retaining clip so it was being pushed out slightly, but I fixed that. The others all seem OK. Will do some more ground testing today.

[DMC5180]

Not sure why you are saying Ground Testing. All Wires ( except Black or trace / Black ) are Live or Switched +12 V. You are looking For Power not Ground.


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[jawn101]

Not sure why you a saying Ground Testing. All Colored wires are Live or Switched +12 V. You are looking For Power not Ground.


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Sorry, confusing two sets of instructions. I have Dave McKeen telling me direct via email to run a few ground checks as well.

I will also test the A/C panel relay socket as you suggested.

[DMC5180]

To keep things Simple, reinstall your Jumper mod to confirm the panels lights illuminate. Then move the jumper wire end from right side location to the Center terminal (87a). Do you get illumination with Key ON? If you don't have lights, you have an Open in the LG/W + 12v feed circuit.

This Not a ground issue.


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[jawn101]

To keep things Simple, reinstall your Jumper mod to confirm the panels lights illuminate. Then move the jumper wire end from right side location to the Center terminal (87a). Do you get illumination with Key ON? If you don't have lights, you have an Open in the LG/W + 12v feed circuit.

This Not a ground issue.


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Just tried this. With the jumper in pins 30/86, I have panel illumination with the LMS turned on. With the jumper in pins 30/87a, there is no light with key on or LMS on.

[DMC5180]

What is LMS?




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[jawn101]

What is LMS?




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Lights Master Switch (headlight button)

[DMC5180]

Lights Master Switch

I figured you'd say, Lighting Management System. [emoji23]

Aka headlight switch.


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[jawn101]

I figured you'd say, Lighting Management System. [emoji23]

Aka headlight switch.


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I didn't make the term up :) Just a convenient shorthand.

So, given that there appears to be a problem with that pin... where is my next stop? The resistor appears to be the next connection on the schematic.

[DMC5180]

I didn't make the term up :) Just a convenient shorthand.

So, given that there appears to be a problem with that pin... where is my next stop? The resistor appears to be the next connection on the schematic.

There are 2 terminals in the Red socket.

One should have power with key ON. Do you recall how you tapped into the LG/W for The DLM mod. (Solder splice or Wire tap)?


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[jawn101]

There are 2 terminals in the Red socket.

One should have power with key ON. Do you recall how you tapped into the LG/W for The DLM mod. (Solder splice or Wire tap)?


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Yep, I checked that. There is power with key on at the resistor. I do remember that I cut the wire and spliced a butt joint. I wish mightily now that I had used a vampire tap so I could have preserved the original wire's integrity and back this out more easily, but there you go.

[DMC5180]

If you have confirmed power at the red socket, you are going to need to pull the bank of sockets up and look at what's going on underneath. You have a bad connection somewhere under there. The butt crimp is suspect to me. Detach and Turn the relay bank over post a photo of the wires between the Red socket and black (AC relay) socket.


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[Bitsyncmaster]

Sorry, confusing two sets of instructions. I have Dave McKeen telling me direct via email to run a few ground checks as well.

I will also test the A/C panel relay socket as you suggested.

I suggested ground checks because his relays (headlight, blower) were only working with some weird combinations. Those problems may be related to the AC light problem.

[DMC5180]

I suggested ground checks because his relays (headlight, blower) were only working with some weird combinations. Those problems may be related to the AC light problem.

Understandable, but when you don't have power on the A/C relay 87a ( the N/C pass thru circuit ) and you DO have power on the LG/W of the Red resistor.
Their is something weird happening between the to sockets.

Time to breakout the DVM for some continuity testing. Both resistor socket wires are directly connected to A/C relay terminals 87 or 87a.

I confirmed the configuration is

Red socket 30 to 87 (A/C relay). R/N wire
Red socket 87 to 87a (A/C relay) LG/W wire


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[David T]

Understandable, but when you don't have power on the A/C relay 87a ( the N/C pass thru circuit ) and you DO have power on the LG/W of the Red resistor.
Their is something weird happening between the to sockets.

Time to breakout the DVM for some continuity testing. Both resistor socket wires are directly connected to A/C relay terminals 87 or 87a.

I confirmed the configuration is

Red socket 30 to 87 (A/C relay). R/N wire
Red socket 87 to 87a (A/C relay) LG/W wire


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If it is working with the jumper (only on when the lights are on) why not leave it like that? Keeps the console cooler and you really do not need that panel lit up during the day.

[DMC5180]

If it is working with the jumper (only on when the lights are on) why not leave it like that? Keeps the console cooler and you really do not need that panel lit up during the day.

Good point, but I'd guess he has LED panel lighting. Being ON all the time doesn't hurt anything. For that matter the Resistor doesn't do anything other that complete the circuit in that configuration.




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[jawn101]

Yes, I already said this. I have LEDs and would like to figure out what's wrong before just shortcutting the jumper mod.

I did test continuity at the resistor. It's perfectly fine between both leads (Lg/W and R/N) at the relay socket and resistor. I also took out my shift plate to get at the rheostat jumper I made and confirmed I have continuity (from rheostat to relay) and voltage there on the R/O lines.

I confirmed the ground in the relay socket straight to battery just for completeness' sake.

I also just checked the voltage in the actual AC light relay socket. It's 0 volts across R/O and Black (ground) with the key in any position. But it goes up to 11.8 when I turn on the lights master switch. However even with the relay and resistor installed this does not illuminate the panel Lights....

[Bitsyncmaster]

The light green/white wire gets power from fuse 10 when the key is on. That wire feed the resistor and the center pin of the AC light relay. The center pin is connected to the light power when the relay is not energized. When the relay is energized it opens that center pin and connects the power from the resistor.

The resistor will probably not make any difference to the light intensity with LEDs. So the relay is not needed if you just jumper (bypass) it. If you don't like the looks of the jumper (I don't either), make the jumper (connection) under the relay socket.

I actually had one customer request a "jumper" made like the potted relays I sell.

[jawn101]

What I can't figure out is why there's no power going to the lamps in the stock config though. Been this way forever.

With the relay installed and lights off, key on, there should be no power at pins 85/86 (R/O and B) on the relay as these are the coil power.

There should be power at 30/87a as this is N/C, right?

Then turning on the lights switch should send power to 85/86 which engages the coil and switches so there is now power on 30/87 instead (N/O)

Pretty simple in theory. But that lack of power in the N/C config is what I can't figure out.

[jawn101]

Don't know why I didn't think to try this before, but when I turn on/off the headlight switch, I can physically feel the AC panel relay click on/off.

[Bitsyncmaster]

What I can't figure out is why there's no power going to the lamps in the stock config though. Been this way forever.

With the relay installed and lights off, key on, there should be no power at pins 85/86 (R/O and B) on the relay as these are the coil power.

There should be power at 30/87a as this is N/C, right?

Then turning on the lights switch should send power to 85/86 which engages the coil and switches so there is now power on 30/87 instead (N/O)

Pretty simple in theory. But that lack of power in the N/C config is what I can't figure out.

You have it stated correctly. You can test if there is voltage on the center pin (87a) without the relay in the socket. If there is voltage then maybe your relay "NC" connection went bad. You should also see power on pin 87 if the resistor is installed.

[DMC5180]

Yep, I checked that.. There is power with key on at the resistor do remember that I cut the wire and spliced a butt joint. I wish mightily now that I had used a vampire tap so I could have preserved the original wire's integrity and back this out more easily, but there you go.


Are you absolutely sure you have Power at RED resistor socket 87a with the key ON?

[jawn101]

I pulled out the relay and tried others, and did a continuity check on the original one- normally closed terminals are normally closed.

With the relay removed, resistor installed, key on, there is no voltage at pin 87a. But the other fuse 10 components work; the AC mode switch and door lock telltale are good

[jawn101]

Are you absolutely sure you have Power at RED resistor socket 87a with the key ON?

No, not sure anymore. My test when I stated that must have been suspect. I now see no voltage there.

[DMC5180]

No, not sure anymore. My test when I stated that must have been suspect. I now see no voltage there.

Okay, now things make more sense.

Deleted previous statements

[jawn101]

Unfortunately on my car there isn't one. This was changed to support Dave's dome module. So I have a yellow wire that receives key-on signal from the Lg/W wires in the resistor. This is also not working, but Dave originally attributed it to a failed dome light module (I do not currently have one installed and am waiting on the mail to bring me a new one)

Are you sure the original dome light module had a Lg/W wire? I don't see it on the schematic.

[DMC5180]

I honestly think you have an issue with the Butt splice.


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[jawn101]

I honestly think you have an issue with the Butt splice.


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But in my defense there, I confirmed continuity from the Lg/W pin of the resistor to the Yellow pin of the dome light module, and it's a double-crimped barrel and I only modified one of the two wires - so I should still see something from the other wire. I can try carefully taking it apart and re-crimping but that's not my preference, the wires are very short and I can't really spare to cut it out altogether.

[DMC5180]

But in my defense there, I confirmed continuity from the Lg/W pin of the resistor to the Yellow pin of the dome light module, and it's a double-crimped barrel and I only modified one of the two wires - so I should still see something from the other wire. I can try carefully taking it apart and re-crimping but that's not my preference, the wires are very short and I can't really spare to cut it out altogether.


The way I see it, you have a BUTT splice which means the LG/W wire was cut to install it. With a single LG/W wire on one end and a single LG/W + Yellow on the other side. If the crimp on the single wire side failed it would cut power to the opposite side.

I know its bugger but your going to need to check it. Do you have a needle pointed Test light that you can poke into the wire insulation of LG/W single wire out of the splice?

[jawn101]

I honestly think you have an issue with the Butt splice.


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Well, shut my mouth. I carefully crushed the splice backwards so I could remove it without cutting more wire and installed a brand new, smaller gauge one. Now the A/C panel lights come on no problem with the key!!!

Thanks Dennis :)

[DMC5180]

Well, shut my mouth. I carefully crushed the splice backwards so I could remove it without cutting more wire and installed a brand new, smaller gauge one. Now the A/C panel lights come on no problem with the key!!!

Thanks Dennis :)

Happy to assist :thumbup:

CASE CLOSED

[DMC5180]

Unfortunately on my car there isn't one. This was changed to support Dave's dome module. So I have a yellow wire that receives key-on signal from the Lg/W wires in the resistor. This is also not working, but Dave originally attributed it to a failed dome light module (I do not currently have one installed and am waiting on the mail to bring me a new one)

Are you sure the original dome light module had a Lg/W wire? I don't see it on the schematic.


No, I think that was an incorrect statement on my part. I have all my relay wires bundled up with Zip-ties and there is one LG/W wire that crosses from the front Relay bank to the Rear relay bank. For some reason I thought it went to the DLM. That said, I may have had some LG/W wire lying around when I did DAVE's DLM and used it instead of the Yellow wire you mentioned. You are correct, it is not shown on the Schematic.