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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 2784
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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Ford F650: 2000 ford f650 with 5.9l cummins diesel. A/c compressor

Customer Question

2000 ford f650 with 5.9l cummins diesel. A/c compressor is engaged/ has power all the time the vehicle is running, even if both pressure switches, and dash controls are all disconnected. Do you have an actual wiring schematic for the a/c system?
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 1 year ago.
My name is ***** ***** I will assist you.Here is the full AC System Diagram at your request.The clutch on this system does get its power from the PCM on this vehicle. You will see that in the diagram. It will be pin 41. Not the ECM, the PCM. They are 2 different modules. I would check the Ford side with the Ford IDS tool and see if there is something wrong with the PCM itself. __________________________________________________________________________________________________________________________You want a 5 star service and I want to provide a 5 star service. Please consider that I can't see, touch, smell, hear, ortaste the vehicle/machine in question. Please provide as much detail as possible and I will provide as much back.The system DOES NOT automatically give me credit from your deposit. A rating is REQUIRED. You are rating me for the information I provide,not the website. I have no control over the site fees, site errors, category errors, or how long it took for a response for these reasons.I am not an employee of this website, so please rate with a POSITIVE (green) rating for me to get credit for assisting you. You still paidfor negative and no ratings I just get nothing.I want you pleased with my service to you so please inform me before rating negative (red) and I will do my best to make it right. Follow upsfor same question are always free.Thanks,Jeremy
Customer: replied 1 year ago.
Thank you for the schematics, but they are not correct.....the low side cycle switch wire colors are black, red w/ yellow stripe,high side switch is a light blue, black wire, the compressor coil is a black w/ yellow stripe,and a black wire. Do you need the vin of the truck.
Expert:  Jeremy replied 1 year ago.
This is the diagram provided from Ford for all 2000 F650 trucks. The colors are not that important. The routing is what is the most important. The power goes from the low pressure, to high pressure, to the PCM. On the compressor it goes from the PCM to the clutch to ground. Check your power in at the low pressure, which should be hot at all times the A/C controls are turned on and no power when off. See if you have that on/of. If not, then you know there is an issue at the main control switch. If you get your on/off like you are supposed to have, then check for the power on/off coming from the high pressure switch to determine if there is a short to power between those 2 switches. If all is good, move to the next.Check the black wire on the clutch to determine that you have a 100% ground at all times on that wire. If so, you are good. Then move to the yellow striped wire and see if the power goes on/off. If not, as you stated, move to the PCM and see if the output for that wire is going on/off to determine if there is a constant coming from it. Also check the input to determine the same to verify there is no short to power going into the PCM.This will determin if there is an issue with the PCM or the signal going to the PCM, or out of the PCM with short to power.Don't be surprised to find the relay is sticking in a constant on position in the relay box. When relays go bad, they can stick on or stick off so I would check it first by swapping with a known good relay and then do the other tests from there.
Customer: replied 1 year ago.
Where would the pcm be located? With this having a 5.9 cummins engine, I didn't think it has a pcm, also where would the ac relay be located? I had removed all relays in the fuse panel below the steering wheel, and under the hood fuse boxes, non would disconnect the ac clutch while running. I traced/ homed out the black/ yellow stripe, 12v compressor wire, and it goes to pin31 of the cummins Ecm plug, which according to schematic per engine sn on quick serve says its "intake heater #2 control... As for the black wire that comes from the compressor,- wire ohm out to the black wire on the high and low side switch
Customer: replied 1 year ago.
I just talked to the local ford dealer, they do not show a pcm listing for this truck, nor an ac relay... None of the wiring schematic you sent me earlier matches up. My conclusion is the schematics you sent me were for a 2000 ford f650 with like a 7.3 power stroke engine in it which would have a pcm...
Expert:  Jeremy replied 1 year ago.
I'm going to opt out for that is the wiring diagram that comes up on my end. It isn't showing any others for the year and model.

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