I have an odd issue with my 1989 Brougham.

The ECC Control Panel operates fine with ignition ON and engine not running.
Start the car and the ECC Control Panel is dead and dark.

This used to happen on rare occasion. Last week it became permanent.

I've been thru the service manual.
The ECC Power Module seems okay, puts out 8v whether the engine is running or not.
The ECC Control Panel connector has 8v coming in whether the engine is running or not.

I'm not sure where to look next. Anyone have any ideas?
I'd sincerely appreciate any suggestions.

 

Is the ECC the dash lights and warnings?
if so my 1996 dims when put in drive
part of the ambient light sensing circuit, annoying
the head lamp switch in 1996 I believe has the sensing circuitry
the schematic for electrical is incredible
I wonder if it can be unwired or rewired to ignore ambient light

 

No. The ECC is the climate control panel. Thanks for the response tho.

UPDATE to OP: Issue is still intermittent.
The ECC always comes on when key is set to ON. When the key goes to START, the ECC goes out (dark, dead, whatever) - which I think it's supposed to do.
After the car is running a few seconds the ECC should come back on but most of the time it doesn't.

Nothing is visibly wrong (ie: melted) with the ECC control panel, programmer or the power module.
The 8v leads at the control panel & power module test good.

Any suggestions are welcome.

 

Here is a snap shot of the 1988 Brougham service manual. Should be the same for 1989. Looks like you need to jump pin 12 of circuit 155 to ground and see if you get a display or not. Since it's intermittent, it should be fixable