Electrical Issues

[Aidan Justin Bowles]

Hello, posting on mobile so sorry if it’s a mess. 

A few weeks ago I purchased a 199 GMC Sierra 1500 Z71. Since than I have noticed a few issues regarding electrical. 
 

The radio has no power but the hr and min buttons show the clock. 
 

The wiper switch does not work but the washer switch does. 
 

Overdrive does not show on the dash, the orange wire is not broken. 
 

The window switch does not work, there are two wires pulled out of the drivers window switch. 
 

There is a wire under the hood by the Ac compressor that does not go into anything (see pic)

 

When I bought the truck the 4wd worked fine. Now the light on the 4wd switch just flashes when I push it. I am able to get it to switch with the shop tool hooked up but not with the buttons on the dash. 

 

I did some troubleshooting and found that the fuse that says radio, along side a few other fuses in the cab do not have power when the key is at the Run position with the truck off.  Also, all maxi fuses are good. A side note, the maxi fuse for “air pump” calls for a 30 and there is a 40 in its slot, also, I did not think it had an air pump. 
 

The scanner tool shows a B1478 (Rap circuit high) and B2647 (Ambient light circuit low). 
 

Also shows ABS pump circuit open (Bad valve assembly) 
 

My question is could this be all tied into one thing or could it be multiple issues?

[jorgef4x4]

That picture you provided is next to the accumulator and as far as I know it isnt plugged since its considered a add on from GM. My own 2002 and my brothers 02 as well as my uncles all have that loose wire pigtail. For overdrive not showing on your dash, most likely a burnt incandescent bulb, common on this year of clusters. The ambient circuit is located on your dash in the middle uptop, a small black bulb of sorts. Changing this sensor has fixed my issue with that in the past. For everything else id follow back to a bad ground or a problem with the Electronic Body Control, which I've linked with my project truck to be a fault in the ecu. 

[Colossus]

Those are digital LCD displays so no incandescent bulb for the gear indicator.  More likely a bad LCD or something on the circuit board. 

 

You need a new 4WD switch.  Very common issue on the early GMT-800s.  My old 99 Silverado had that issue.

 

You likely also need a new multi-function switch (wiper/turn signal)

 

I'd also get a new window switch and figure out those wires.  Window switches failing was also somewhat common.  Someone may have tried to repair it or perhaps prevent it from being used (bad regulator?)

 

There might have been an aftermarket radio installed at some point and then the previous owner pulled it out and put the stock radio back in, and didn't wire it up right. 

 

Multiple issues.

 

But I'd also check to see if any wires look like they've been gnawed on by rodents. (mice)  You'll have to look closely all over the place. 

 

 

 

 

[Aidan Justin Bowles]

So I did more digging. The two wires I found not connected to anything are in fact to a speaker that someone removed. The wire in the engine bay is for an air pump that the truck does not have. 
 

I also held 12 volts to the RAP wire of the window switch and it started working. I also held 12 volts to the radio fuse and the radio started working. I’m starting to think the RAP relay is bad and is triggering the RAP circuit high code. Is there a way to test this theory? I don’t see a RAP relay to remove but the device manual says there is one, just will only say it’s in the LBEC.