DavidDeBord

Greetings Ya'll!

This is my first post & more than likely there will be many more, as I rebuild my van

I bought a wrecked in the front end 2007 Chevy Express G2500, & after having straightened the frame, replaced the bumper & grill, lights, & hood, the Dash Cluster Gauges, & Indicator lights which had no problem before, then began to operate in an insane manner! The Temp., Oil, & Battery Gauges would rise & fall, & the "Security", "Check Engine", & "Chimes", would go on & off. I put a "load" on the system by tuning on the headlights, heater, & radio, but they had No Effect on what was happening, BUT,...... when the Gauges fell to 0, the radio also quit working every time, but the Heater Blower, Hazard lights, & Headlights continued to operate with no problems.

I found by accident that by pressing on the brake pedal, & releasing it that everything would return to normal, including the radio for about 3-5 seconds, but then the "Van Possession" would then return. Again, nothing happens to the Hazards, Blower motor, nor Headlights.

Now here's Th' Kicker,... When I depress the Brake Pedal, the Dash Cluster works perfectly, as does the radio. When I release the brake pedal, then within 3-5 seconds the Dash Cluster & Radio then start the whole insane process over again.

Has anybody experienced this, & if so, how did you fix this nightmare? Is there a ground that may have become disconnected during Our Repairs, that is specific for the Dash & Radio?

And, can anyone tell me where to get the Dash/radio wring diagram?

Much Respect

mountainmanjoe

sounds like you have a fault in the brake switch.
You can check for schematics are on gmupfitter.com

DavidDeBord

Greetings Mountain!

First,... I can not thank You enough for that link, & I've downloaded the Electrical & Body PDFs, & printed up the schematics for the Grounds, & Devices.
Now that I know where to look,... It's like a light being turned on, in a dark room.

As far as the brake switch, do you have any data for it, such as Manufacturer, Model/Serial Numbers, NO & NC Contacts, as well as any resistance values?

And again, THANK YOU SIR!

William Kisselstein

Sounds to me like a ground issue. A brake light switch is like $20 on Rock Auto, cheap to change (or get one at a wrecking yard) and see if that solves the problem. Going to have to look over the wiring and make sure something's not shorted together or broken from the accident. Could be a wire is broken and the power feeds through the brake light switch when it's engaged.

mountainmanjoe

you should be able to find part info on rockauto.com

DavidDeBord

Thank You William & Mountain!

I'm looking at the Rock Auto site now & the GM switch D891A is $18.53, which I'll order,but as far as any deeper technical info such as Manufacturer,which I'm thinking is ACDELCO , NO/NC Contacts, SP/DP switching, etc., isn't there.

I gotta say here, that one of the best Teachers that I had for the HVAC/Refrigeration trade taught me that when a Bad Compressor, Reversing Valve, TX Valve, Contactor, etc.,etc. ,was replaced, that a lot could be learned by taking the failed part,apart. And, in My Belief,he was correct in that Teaching. And, I'm curious as to how, & why the switch failed, if it does turn out to be the problem.

Correct me if I'm wrong,but any voltage that passes through that switch should be within 12 Volts, & not the approximate 5.2 volts used in the motor sensors etc.?

mountainmanjoe

that can probably be deduced from the the schematics. Why do you want to know?

DavidDeBord

Any data available about the brake switch, as in normal voltages, to be found at what pins at the input connector. From the data that I've gathered from the GM PDFs, (& again Thank You for that link Mountain!) Pin A4 at the dash cluster receives Input from the brake switch. What I don't know yet, is if this is 12 volts, or the 5.2. From the schematic I also know that the dash cluster has two grounds,which are located at pin B4 & B3, & that these grounds connect at the #350 &#351 ground terminals located at the "Left Kick pad". I think that one of them, via the wiring harness, is also to be found at the brake switch.

I also tried yesterday to find an "Internal Schematic" for the brake switch, so as to get an idea of how it would fail, & cause the dash & radio problem. But,... so far the best data available is what I found at Rock Auto.:

https://www.rockauto.com/en/moreinfo...=10474&jsn=943

Much Respect Mountain!

mountainmanjoe

If you look on page D-53 of the electrical manual, there is the brake switch in the top right corner.
The input pins are labelled IGN-1 (hot when ignition on), and BAT+ (battery positive). These are both 12 Volt circuits.
You can also see the pins are being fed from the fuse block. Everything on the fuse block is 12V. There is also a label PWR DIST, so that you can refer to the Power Distribution schematic (hint: it's all 12V)
5.0V is typically used for signals and logic, not power distribution (eg sensors, control modules etc.). The only source of low voltage on cars will be PCM, BCM etc.

William Kisselstein

What needs to be determined is if:

A - the lead from brake switch to cluster should always be hot and is for some reason shutting off. At this point you may as well change the switch when the new one comes and that will probably rule this in or out. Alternatively a voltmeter on the lead, depress pedal, let off, watch what happens, would show.

B - if it's supposed to cut off, where does the cluster get power from when the switch is turned off? In this situation clearly whatever it should get power from is damaged.

Just for the heck of it, we did check the fuses first? IIRC there's one for the cluster. Probably you did but it's an easy thing to forget.