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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3304
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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I have a GMC T7500 and need a diagram of the relay box (9)

Customer Question

I have a GMC T7500 and need a diagram of the relay box (9) in my truck.
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 year ago.

My name is ***** ***** I will assist you.

Gmc site is currently down due to updates. If you can provide full VIN, once it is up, I can see what diagrams are available.

GM has a lot of their servers down because it's the one day they have a mandatory closure for all shops and plants. They go down every year on Christmas. That's why response is late, but I didn't want you waiting in the dark.

Customer: replied 1 year ago.
Hi Jeremy, here's the details: 2001 GMC T7500 VIN: 1GDJ7C1C81J510159 The relay box is 9 slots (3x3) and upper left was the one that was where a small noise was coming from under. This is one I replaced. I found a part store that they only $8.95 and was thinking of just replacing all. The problem started after I started the truck then went to use lift gate. It's switch has been tricky and sometimes required making sure the plug going into the motor box for the lift but this was different. Like it was locked up and quickly killed the truck. Then trying to re-start the grounding out starts when moving key from accessory to start. (Bad ignition switch?) Looking like I will be tracing down a ground short either between the ignition to it's relay or between the lift gate motor to it's relay? But need to know which relay is to what? Eight of the relay's are identical in brand and I think #'s with only the top right being a different brand. Is there an easy way to tell if a relay is bad other than switching out with a new one? When I got the truck to start once (let idle for 30mins) I notice all the relay's were warm but the top left so that's the one I replace with new. Just guessing here and it did not fix problem. Thanks for any help, electrical problems are the worse to diagnose. Sincerely, ***** *****
Expert:  Jeremy replied 1 year ago.

I don't know why this has me as a opt out because I didn't opt out...


This is all that the GM site offers for the fuse box diagram. I hop it helps you. It shows what fuse and what coler wires are for the fuse. They don't go into the details like Ford does with the pictures and all.

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