'88 GMC K1500 4x4
5.7L/350ci TBI engine

It has the premium Stereo System from GM. Inlcudes AM/FM, Remote Cassette & Equalizer combo, 4 speakers.

Overt teh last few years thedisplay for both of these moduals would blink irratically and have little or no control. Ambient Temp seemed to be part of the problem in the past. Wouldn't work when cold, (say below 40'F), and would work when warm. or you could give it a "bump" and it would sometimes work, but lately not so much.

Now the radiomodual does not work at all. Just displays the incorrect time and will not turn on.

TheClimate Control modual just blinks irratically and doesnot control temp. It will control the fan speed.

I looked at the wiring diagram and both units (and most of the dash and PW controls) show they ground at S207 then on to junction G202.

Anybody know where these junctions are located???

Is S207 a solder, or crimp connection?

Are there other ground connections I should check?? (other than the battery & passenger side frame rail in engine compartment, the two grounds under the plastic cover on the passenger side firewall)

The truck being so old, I am thinking it may be a ground issue.

If it turns out that it's the moduals themselves that are bad, where do I go to get a replacement or get it fixed?

I have put in requests on a few auto salvage sites but I never get a reply.


Thanks for your help.....

 

Still looking for where the G202 & S207connection points are at on the truck but I did get the clusters working.

In the process of removing my dead clusters to test new ones I decided to take them apart to see if there was anything I could fix myself. Burnt Resistors, Capacitors, etc.
When I took them apart I looked over the boards with a flashlight and found nothing out of the ordinary. I did noticed they both have the "display cards" plug into the "mainboard" of the cluster. I noticed a very small amount of "buildup" or wear maybe, on the pins that make the connection after being plugged in.
I cleaned these with one of those 3M pads and made them all nice and bright.
Plugged them back in and while holding my breath I turned them on. Both of them came back to life and control perfectly!!!!!!
These marks were very small. It looked like the square pins have worn over the years causing a small 'wear mark' & 'grit' to appear, causing the partial connection. Which would explain the flashing display, and why it would work once in awhile after I gave the dash a firm "bonk".
So for those who have a similar display problem, on a similar vintage truck. Take a shot at doing what I did above.
Yea, pulling them out of the dash can be a fun project. Be aware you will need to unplug switches after you pull the dash panel out enough to get your hand back there. Switches being head/running lights, fuel tank switch, rear defogger, etc. They don't give you alot of room but if you stand on your head and contort your arms into a pretzel, they do uplug. It took me about 4 hrs from start to finish.

Big Red rides again. . . . Well, after I get the A/C leak checked and charged back up it will.

 

They are very succeptible to power removal...as you've discovered...

I'm not 100% sure on g202...but any 200 means that its in the cab.