Hello, First off I know that John in RI is the subject matter expert, but I thought I'd ask you guys to see if anyone can help. About a month ago I purchased a 1984 Berlinetta and have been working since to correct a number of minor electrical issues in the car. A few still have me stumped. Initially, I had thought that my gauges were all shot, none of them functioned correctly and just pegged themselves when the car was turned on. The tach would never display RPM's on the dash either. The more I drive the car, every once in a while I get some level of function from the gauges! The volts gauge works most often, but not always. The fuel gauge is hit and miss, as well as the water temp gauge, and I've only seen the oil psi gauge read correctly a couple of times. None of them work at the same time, and they are all intermittent. If one is functioning, it might stop while driving down the road-- or it may quit once the ignition is turned off and back on. Any idea? Also, I found that I can get the tach to operate ONLY when the parking brake is engaged! Any thoughts on this one? My digital read-outs fade when the headlamps are turned on, and I've read that this is due to the light module going out. Can it be rebuilt or refurbished, or do I have to track down a new one? Thanks ahead of time!

Intermittent and irregular as everything is, would warrant a thorough inspection of the ground(s) to the gauges and dash.... An extra ground wire from the gauge panel ground to the firewall or a brace under the dash someplace may help, too. Grounds tend to attract corrosion, doesn't take much to effect how the gauges work.....

Yeah, I've been meaning to tear the whole dash out and take a look.

Anybody know where exactly the Light Module is located?

Hi Austin,

The Light module is mounted "piggy back" to the ECM. To remove it you'll need to remove the passenger side 'hush' panel, then unscrew the ECM bracket from the dash housing and pull the ECM/Lighht Module down and towards the center console.

If you do end up pulling that cluster out for a better look than check the printed circuit on the back of the cluster. The "fail point" on the printed circuit is right at the printed circuit plug where it connects to the internal circuit boards. You would need to pull the circuit boards from the cluster in order to see this area ( BE SURE THAT YOU GROUND YOURSELF before touching ANY circuit boards !

P.S. That Tach/E-Brake thing is still making me scratch my head !!!

Thanks John! Once I pull the light module, is there any way to refurbish or repair it, or is it pretty much shot if it's acting up?

All of these digital 80's electronics and doo-dads have been making life interesting. I'm shooting a trouble code 54 right now, which should have something to do with a mixture control solenoid. Is this located on the carb? I tried calling numerous parts stores and they all said that this solenoid is a dealer part, that they couldn't order one.

I have never repaired a dead light module...... I'm sure it can be done - but I've never met the dude that can do it. ( I have never soldered anything ! ) I've got a bunch of these things in my "core" collection, And someday I will be forced to find someone cabable of repairing them.

The only thing on your list that the light module is related to is the dash/console/paenl lighting once the headlights are turned on. The light module sends a variable signal to those areas so the brightness can be adjusted up and down. Usually the dimmer circuit simply fails and there is no Digital display or panel lighting at all when the headlights are active.

What you should do is gain access to the ligth module wiring and probe the "dimmer" circuit wire with a voltmeter while adjusting the rheostat dimmer on the Blinker pod to see if the voltage changes (as it should)



http://berlinetta.info/help/LightModule.jpg

Thanks for the diagram!