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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3320
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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My blower motor runs on its own when I start my truck I

Customer Question

My blower motor runs on its own when I start my truck I pulled the bunk fuse now I can work my cab controls but my ac don't kick on 2004 peterbilt 379 exhd
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 year ago.

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

Which blower runs all the time? Front or rear?

When you pulled the fuse, did you leave it out? If so, when you put the fuse back in does the A/C then work properly?

I'm trying to narrow down on where to look and what to check further.

You want a 5 star service and I want to provide a 5 star service. Please consider that I don't know your skill level as well as I can't see,
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Customer: replied 1 year ago.
Front blower my ac clutch burn up now my ac compressor locked up now im going to replace ac unit dryer orvice but the blower quit acting up when I put a shorter belt on it to bypass the compressor so I could get home but my bunk controls don't work at all now peterbilt told me to replace the compressor and then ill have to troubleshoot from there what do you think
Expert:  Jeremy replied 1 year ago.

I agree on replacing the compressor to troubleshoot the remainder, but if the compressor burned up because the compressor stay engaged all the time, that could be bad. I would put a headlight onto the A/C circuit and shine it up to the cab. Then I would pull the A/C control panel out of the dash and look on the back of it to see if there are any wires melted on the plug which could keep the fan and compressor engaged. Also replace the blower relay and the A/C relays, just in case one is sticking and causing power to hold onto the system. Then I would troubleshoot from there.

Go HERE if you need any diagrams for your unit. Scroll down and look on the right and you will see a section for schematics. You will find all you need there. These are the exact same ones that we have in the shop.

Expert:  Jeremy replied 1 year ago.

Do you still need assistance with this?

Customer: replied 1 year ago.
Expert:  Jeremy replied 1 year ago.

Thank you for the reply. Have a great day!

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