Car at shop - No Instrument Cluster lights after new BCM - Updated

[doity]

I had my 88' in the electrical shop for a number of problems, the biggest was that the dash and CRT would not come on but would occasionally come on for seconds and then back off.  I actually drove it like that for a couple of months as the car was still functional and the headlights still worked but once winter came without the HVAC system I was screwed.  After some tracing they narrowed it down to the BCM and they ordered a new one.  Well, he says that the CRT is now working as well as some things like the chime when the door is open, etc., but there are no dash lights.  He said it would need a few hours of digging to find the problem and at the shop rate of $$$ I said that I would post here to pick the brains of the forum members first to see if there is something obvious that they should look at.  

 

They have the Reatta service manual but he says that it is a bit confusing and/or cumbersome to work with.  Is there any logical places to check first so they to get the dashboard back up and working?  Much thanks!!

Edited June 11, 2017 by doity (see edit history)

[Dashmaster]

The term dashlights, Do you mean the background lighting of the switches or are you referring to the main dash display? The back lighting is controlled by a photocell sensor in the top of the dash, You need to cover it so it thinks its dark outside to see if its working. If the senor is bad they will not work.  

[89RedDarkGrey]

10 minutes ago, doity said:

They have the Reatta service manual but he says that it is a bit confusing and/or cumbersome to work with

 

That says a lot about "Mechanics" we have to rely on now days. Back in '88 the FSM was the only resource for Reatta info, and they worked it out. Everyone's so reliant on the Internet for everything- we've been dumbed down as a society.

[89RedDarkGrey]

3 minutes ago, Dashmaster said:

The term dashlights, Do you mean the background lighting of the switches or are you referring to the main dash display? The back lighting is controlled by a photocell sensor in the top of the dash, You need to cover it so it thinks its dark outside to see if its working. If the senor is bad they will not work

 

http://reattaowner.com/roj/component/content/article/index.php?option=com_content&view=article&catid=61:digital-dash-panel-a-crt&id=181:instrument-panel-lights-troubleshooting

 

http://reattaowner.com/roj/component/content/article/index.php?option=com_content&view=article&catid=59:interior-lights&id=192:twilight-sensor-photocell-replacement

 

My own work on my '89-

 

 

[89RedDarkGrey]

Ask the Shop to install the OLD BCM, then verify the "dashlights" come on like before?

[doity]

Sorry I was running late today and maybe did not make myself clear.  I did not mean the photocell as they already replaced that.  I mean the main dash display with the speedometer, fuel gauge, odometer, clock, etc.  

[89RedDarkGrey]

Have all of the grounds (under seats, under hood) been repaired and cleaned?

[D-a-n-i-e-l]

Did you swap bcm proms? If I recall (years ago) if the prom is missing or from a different year the dash will not work. 

Once again it has been years sense I messed with the bcm proms

[doity]

I got at call from the shop yesterday and they traced it to a bad central power supply.  I wonder if that was what it was after all and not the BCM?   They said that after the new BCM was installed that the CRT started working but not the IPC.  Hmm.  He told me that the Instrument cluster was not getting the 7 volts that it needed from the CPS.  

 

This might be good info for someone with the same problems and might help in saving troubleshooting time.

[89RedDarkGrey]

7 minutes ago, doity said:

they traced it to a bad central power supply

 

http://www.rockauto.com/en/catalog/buick,1988,reatta,3.8l+231cid+v6,1019898,electrical,power+supply+module+(tipm),13581

 

That's great news