Im having issues with my idiot cluster, the lights don't come on in the test phase with the ignition on but the engine not running. I have re-soldered both the CPU and the Cluster itself and it work for about 20 minutes after I put the CPU back in. The horn and key/lights on beep still work. So im lost now anyone have any ideas?

 

Update. It seems that the CPU I have is messed up and shorting its self out. When sitting it drains all its battery, and when running the alternator cant keep up and it wont charge the battery. I have had the alternator bench tested and it passed both times. Does anyone have any ideas on this? The CPU is out of my 88 so I have the original one still, Im going to put it back in tomorrow and see if that fixes it, but it needs re-soldered too.

 

W/key to on and the engine off the White/Black wire in the 7 wire CPU plug should have a ground on it. If it does not then the idiot lights will not light up. You can jumper a ground to this pin and see if that changes anything or you could measure the voltage on this wire and it should be close to 0 volts (usually it is 1 to 2 volts or so but definitely not 12 volts). The W/B wire comes from the alternator and if the voltage is high (close to 12 volts) w/key to on and the engine not running then there is a problem w/the alternator or the wire in question is receiving voltage from coming in contact w/another wire that has voltage. The Meter fuse also needs to be good for the lights to turn on. If voltage is placed on the Y/L wire in this CPU plug then the lights should turn on. The other possibility is if the Black wire in the CPU plug, which is a ground, is not doing its job as this is another cause for the lights to not turn on when they should.

 

i hate to say it, but you may have to take the dash out and do i visual check on the wiring!