• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Window switch - 01 Sierra - Questions on how it operates

SnowDrift

SnowDrift

Ultra Conservative. ULTRA!
Messages
3,226
Reaction score
4,208
Location
Central Ohio map dot
I put my driver side window down last night and it would not go back up. I could hear clicking in the switch, but nothing else. I put in a switch from a buddy's truck and it worked fine, so I put the window up. Immediate problem solved.

Now the question portion - when I was testing for power wires, I had a standard test light that I grounded to the dash. I found the power coming in, but then when I went to touch another terminal, the passenger side window went down. I went to the next terminal and the passenger side window went back up. Is this normal?

I'm 99% certain it's the switch, simply because the donor switch did the trick, but the part where the grounded test light was able to activate the passenger side window is puzzling to me.
 
GMT-800 trucks do not use a standard window switch where it powers the motors directly. The window switch sends a signal to the BCM, and the BCM in turn sends the power to the window motor. By probing with the volt meter you were simulating the switches signal to the BCM. Be careful because you can blow your BCM doing that stuff if you're not careful.
 
Haha, yeah. Um.. I can attest to what Ferm is saying. I was trying to figure out the system over a stupid bad drivers switch that later I figured just wore out. When I figured out the damage I had done, my test light hit a brickwall at about 82mph.
I will never again ‘probe to learn’ a system. Schematics are golden, even though reading them isn’t a fun thing.
 
I had a notion I would go and attempt the same with dad's truck today, with a known good switch, to see if I could duplicate this action, but if there is such a risk, then I won't do so.

It sounds like I would be safe to throw a switch at it, then, if this type of function is normal. Would you agree?

All was doing was grounding that circuit and allowing the completion, by how it sounds. I don't read electrical schematics well, so this is the reason for my question. I started to post this, below, but I think some of the circuitry changed from '01 to '05 and I think someone said this one below is from an '05.

circuit.PNG
 
I dont know what that diagram is, but it sure doesn't look like what I seen in my 01 diagrams when I was going over my parts truck. You have to be real careful because some of these are 5 volt systems that run to the bcm. I know 03+ use door modules where everything ties into the j1850 data bus, and its all class 2 data signals that do everything. The system is much more complicated, but it uses far less wire overall, and is all controlled via a central controller(bcm).
 
Refurbished switch fixed it and my window went back up. I noticed, though, that the backlighting didn't work on the new switch, so I'm sending back for a replacement. Switch City USA was the refurbish company. $20 for the switch seemed reasonable - hopefully, they'll make it right and send one where the lights work.
 
You must log in or register to reply here.
Back
Top