Instrument cluster blues
Thread Starter
Advanced
Joined: Dec 2021
Posts: 97
Likes: 2
From: Atlanta GA
Instrument cluster blues
C4 1985
So, I installed new bulbs in my cluster, put the cluster back together and reinstalled it in the car (just plugged it in without reassembling all of the bezels etc.) Now, I get nothing on the cluster. The bulbs do not come on at all. I did notice that once of twice as I turned the key back towards me (as if shutting off the vehicle) I get a full light up but not reproducibly.
I assume that since I saw flashes there is some working integrity (as above) but I can’t get it to stick. I would say that it was brighter when it flashed on compared to before new bulbs put in.
I am reasonably certain that the bulbs were put in correctly and that I put the boards back together the right way.
Any Suggestions?
C
So, I installed new bulbs in my cluster, put the cluster back together and reinstalled it in the car (just plugged it in without reassembling all of the bezels etc.) Now, I get nothing on the cluster. The bulbs do not come on at all. I did notice that once of twice as I turned the key back towards me (as if shutting off the vehicle) I get a full light up but not reproducibly.
I assume that since I saw flashes there is some working integrity (as above) but I can’t get it to stick. I would say that it was brighter when it flashed on compared to before new bulbs put in.
I am reasonably certain that the bulbs were put in correctly and that I put the boards back together the right way.
Any Suggestions?
C
Drifting
Joined: Jan 2021
Posts: 1,312
Likes: 383
From: Northern California
I would start by undoing battery, then disconnecting and reconnecting the main harness connectors on the side of the dash unit. Having worked in IT a long time I can tell you that reseating cables often helps. Then see if you still have the same problem and report back.
Thread Starter
Advanced
Joined: Dec 2021
Posts: 97
Likes: 2
From: Atlanta GA
c
Thread Starter
Advanced
Joined: Dec 2021
Posts: 97
Likes: 2
From: Atlanta GA
So that is a good question. Which pins in the connector does one test to see if there is power and ground? Can you tell me or do you have an illustration that demonstrates? I did try to reseat the connectors but it didn't make a difference.
C
C
Drifting
Joined: Nov 2018
Posts: 1,787
Likes: 579
From: Mays Landing, NJ
On your 85 I have no clue which pins are hot and ground, but hopefully someone comes along that can advise you., I do think however that checking proper power to display should be your first step.
Team Owner
Joined: Sep 2003
Posts: 25,373
Likes: 2,734
The FSM has correct diagnostics for the Cluster 'pin-out' and I don't believe you have BUT I'm quite sure Bryan (Batee.com) includes that in his offerings. You no doubt should go there and spend some time. Is there a 'solution' there? I'd think so!
Racer
Joined: Mar 2020
Posts: 387
Likes: 148
From: Langton, Ontario, Canada
2025 C4 of the Year Finalist - Unmodified
The fact that you were inside your display is giving me a bit of a clue that this is where your problem is, and you may have to remove the display unit (again) and have another look inside.
You need to look at the line of pins on the upper left corner. The lights are powered through these pins. If you see any that are discolored dark, due to heat discoloration, that may be your problem. The springs inside the sockets get weak and heat up with high levels of resistance. This may be why they showed dim for a bit. One way to fix it would be to take a dental pick to the sockets and try to pry them out a bit to contact better. It's a temporary fix at best. If a pin or its socket is obviously black, you could also solder a wire onto the pin base and socket base, and then put an insulated spade connector, male and female on them to bypass the pins. You'll have to manually take them apart in the future if you ever go into it again.
Good luck!
You need to look at the line of pins on the upper left corner. The lights are powered through these pins. If you see any that are discolored dark, due to heat discoloration, that may be your problem. The springs inside the sockets get weak and heat up with high levels of resistance. This may be why they showed dim for a bit. One way to fix it would be to take a dental pick to the sockets and try to pry them out a bit to contact better. It's a temporary fix at best. If a pin or its socket is obviously black, you could also solder a wire onto the pin base and socket base, and then put an insulated spade connector, male and female on them to bypass the pins. You'll have to manually take them apart in the future if you ever go into it again.
Good luck!
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