Dash lights only work when lights off
11-10-2010, 03:53 PM
#16
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The only other items I saw during my 45-minute search to see if this topic already had a thread was:
1) Apparently there is a cluster of wires/connections (behind/below?) the clock...someone said to pull the ashtray unit out and check all connections behind there and clock area. Also, maybe something got disconnected during radio swap/re-installation work?
2) Another post said to pull every fuse related to lights and not just check them visually, but check them with a meter for continuity.
3) ...the obvious, check to see if wire at dimmer is shorted to ground or has too much resistance (dreaded green wire syndrome). My wire to the fuel pump had the green monster...had to run new one a few months ago.
4) Possibly the light sensor above the gear indicator lights is causing a fault (I may have misread this...might be related to some other issue). The person said to shine a flashlight unto the sensor to see if the dash dims when they are on.
5) Related to stereo work / someone may have tried to connect an aftermarket radio's light to the headlight switch fuse area and shorted/disconnected something by accident.
Again, I only searched for about 45 minutes; there may be other threads that answer this better.
1) Apparently there is a cluster of wires/connections (behind/below?) the clock...someone said to pull the ashtray unit out and check all connections behind there and clock area. Also, maybe something got disconnected during radio swap/re-installation work?
2) Another post said to pull every fuse related to lights and not just check them visually, but check them with a meter for continuity.
3) ...the obvious, check to see if wire at dimmer is shorted to ground or has too much resistance (dreaded green wire syndrome). My wire to the fuel pump had the green monster...had to run new one a few months ago.
4) Possibly the light sensor above the gear indicator lights is causing a fault (I may have misread this...might be related to some other issue). The person said to shine a flashlight unto the sensor to see if the dash dims when they are on.
5) Related to stereo work / someone may have tried to connect an aftermarket radio's light to the headlight switch fuse area and shorted/disconnected something by accident.
Again, I only searched for about 45 minutes; there may be other threads that answer this better.
Best,
Rob
11-22-2010, 12:21 PM
#17
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Thread Starter
Found the problem
It was as suspected...the dimmer for the dash.
I bypassed the dimmer and all the lights came on that were suppose to when parking lamps or headlamps are on.
I'm going to order a dimmer...didn't look easy to replace though, without taking apart more stuff. I'm going to get a small mirror to see what holds it in place.
Thanks for everyone's help
It was as suspected...the dimmer for the dash.
I bypassed the dimmer and all the lights came on that were suppose to when parking lamps or headlamps are on.
I'm going to order a dimmer...didn't look easy to replace though, without taking apart more stuff. I'm going to get a small mirror to see what holds it in place.
Thanks for everyone's help
11-23-2010, 06:01 PM
#18
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Thread Starter
I forgot to mention a few observations.
1) My digital clock started to show time (first since I bought the car in March), but only with parking/headlights on. I'm guessing there is a loose connection on the back???
2) Does anyone know if the aux a/c dials have a back-light?
3) How about the digital clock back-light?
4) How about main a/c fan switch?
5) How about the headlight switch?
...these are the only switches which don't light up/don't know if they are supposed to
I did notice the seat memory buttons also now light up.
1) My digital clock started to show time (first since I bought the car in March), but only with parking/headlights on. I'm guessing there is a loose connection on the back???
2) Does anyone know if the aux a/c dials have a back-light?
3) How about the digital clock back-light?
4) How about main a/c fan switch?
5) How about the headlight switch?
...these are the only switches which don't light up/don't know if they are supposed to
I did notice the seat memory buttons also now light up.
11-23-2010, 06:20 PM
#19
Electron Wrangler
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I forgot to mention a few observations.
1) My digital clock started to show time (first since I bought the car in March), but only with parking/headlights on. I'm guessing there is a loose connection on the back??? >>>YES Sounds likely
2) Does anyone know if the aux a/c dials have a back-light? >>>No - they are just black plastic ***** - (pull them off)
3) How about the digital clock back-light? >>>YES
4) How about main a/c fan switch? >>>No (AC on/off switch yes)
5) How about the headlight switch? >>>YES (always on with ignition)
...these are the only switches which don't light up/don't know if they are supposed to
I did notice the seat memory buttons also now light up.
1) My digital clock started to show time (first since I bought the car in March), but only with parking/headlights on. I'm guessing there is a loose connection on the back??? >>>YES Sounds likely
2) Does anyone know if the aux a/c dials have a back-light? >>>No - they are just black plastic ***** - (pull them off)
3) How about the digital clock back-light? >>>YES
4) How about main a/c fan switch? >>>No (AC on/off switch yes)
5) How about the headlight switch? >>>YES (always on with ignition)
...these are the only switches which don't light up/don't know if they are supposed to
I did notice the seat memory buttons also now light up.
11-23-2010, 06:29 PM
#20
Advanced
Thread Starter
Thanks for the quick/informative response. Your answers are pretty much what I figured, except for the headlight dial...I figured that should be lit when headlights are on so you can find it quick, in case you want to turn off. I see Porsche's logic though...
I read somewhere to pull out the ashtray assembly to check the clock lights / I'll post my results. Glad to know the clock works though, I almost bought a used one for $$$...I figured it went bye, bye / wasn't meant to work 21+years...
I read somewhere to pull out the ashtray assembly to check the clock lights / I'll post my results. Glad to know the clock works though, I almost bought a used one for $$$...I figured it went bye, bye / wasn't meant to work 21+years...
12-04-2011, 09:58 PM
#21
Archive Gatekeeper
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Drove the GTS for the first time in about a month yesterday, and coming home at dusk realized that I had no lights for anything in the center console (HVAC head, clock, ashtray). A few weeks ago, I did take apart the steering column a bit to see how it all goes together, perhaps that wasn't such a good idea... 
Don't recall touching the dimmer but obviously will have to double check. I hates them electrons....
Don't recall touching the dimmer but obviously will have to double check. I hates them electrons....
12-21-2011, 05:55 PM
#22
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I have seen this problem pop up a number of times. I had this problem also, but I figured it out. Here's my official trouble shooting write-up:
Problem: Dash lights (the back lighting) go out when headlights are on. Dash light works fine when headlights switched off. Digital dash display works fine in all cases, this is a back-lighting problem only.
Car: 90GT
Fix: There is a connector on the firewall above the foot pedals. This connector gets loose (it does not come off). Wiggle the connector and you get the lights back. You need to lay on your back with your head/back where your feet normally are (not an easy position). The connector is right on the firewall and pretty high up above the pedals (not easy to see). Have not permanently fixed it so I need to get under there and push the connector on every now and then.
Try this before you tear out your pod or the dimmer.
Problem: Dash lights (the back lighting) go out when headlights are on. Dash light works fine when headlights switched off. Digital dash display works fine in all cases, this is a back-lighting problem only.
Car: 90GT
Fix: There is a connector on the firewall above the foot pedals. This connector gets loose (it does not come off). Wiggle the connector and you get the lights back. You need to lay on your back with your head/back where your feet normally are (not an easy position). The connector is right on the firewall and pretty high up above the pedals (not easy to see). Have not permanently fixed it so I need to get under there and push the connector on every now and then.
Try this before you tear out your pod or the dimmer.
12-22-2011, 01:04 PM
#24
Racer
Join Date: May 2011
Location: West Chester Ohio
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I have similar problem on MY 86. Only time I've seen the intruments lit was when I had passenger side headlight burn out! when that was fixed they didnt work again.
It's on a long list of things to do this winter!
Jc
It's on a long list of things to do this winter!
Jc
12-22-2011, 10:44 PM
#25
Three Wheelin'
Still no solution. I have an 89. There is no connector on the firewall. The dash dimmer varies between around 5-15 ohms (or kohms, didn't look). No blown fuses.
Unless I get some help here I'll be driving around without dash lights.
Unless I get some help here I'll be driving around without dash lights.
04-13-2019, 09:51 AM
#27
Rennlist Member
I have seen this problem pop up a number of times. I had this problem also, but I figured it out. Here's my official trouble shooting write-up:
Problem: Dash lights (the back lighting) go out when headlights are on. Dash light works fine when headlights switched off. Digital dash display works fine in all cases, this is a back-lighting problem only.
Car: 90GT
Fix: There is a connector on the firewall above the foot pedals. This connector gets loose (it does not come off). Wiggle the connector and you get the lights back. You need to lay on your back with your head/back where your feet normally are (not an easy position). The connector is right on the firewall and pretty high up above the pedals (not easy to see). Have not permanently fixed it so I need to get under there and push the connector on every now and then.
Try this before you tear out your pod or the dimmer.
Problem: Dash lights (the back lighting) go out when headlights are on. Dash light works fine when headlights switched off. Digital dash display works fine in all cases, this is a back-lighting problem only.
Car: 90GT
Fix: There is a connector on the firewall above the foot pedals. This connector gets loose (it does not come off). Wiggle the connector and you get the lights back. You need to lay on your back with your head/back where your feet normally are (not an easy position). The connector is right on the firewall and pretty high up above the pedals (not easy to see). Have not permanently fixed it so I need to get under there and push the connector on every now and then.
Try this before you tear out your pod or the dimmer.
I cannot find this on my 90. Anyone have pictures?
04-21-2019, 02:05 PM
#28
Same problem
I've been dealing with the same problem on my'89 for a while. Now it's happening on my GTS. Dash lights work fine when lights are off but go dark when the parking lights or regular lights are switched on. My dimmer works with the console lights, which are still working so I'm not sure how that would be a problem. Guess I'll try and figure it out today.
04-21-2019, 04:52 PM
#29
Rennlist Member
I've been dealing with the same problem on my'89 for a while. Now it's happening on my GTS. Dash lights work fine when lights are off but go dark when the parking lights or regular lights are switched on. My dimmer works with the console lights, which are still working so I'm not sure how that would be a problem. Guess I'll try and figure it out today.
