E350 SD AC question: PLZ READ< detailed info

got a retired diesel mini school bus as my work truck. im pretty sure the ac worked when i got it, but it sat in my driveway for 3 months while i was waiting for the changed title to come from the state. Looks like an aftermarket replacement compressor. The clutch would never engage, so after troubleshooting to much pressure, not enough pressure, ect ect, i discovered that there was no power to the plug on the compressor. So i ran an indipendent hot from an unused switch that was once part of the schoolbus light system, (none of the schoolbus related stuff exists anymore)and bingo! clutch started engaging. i thought, great, i finally have AC. except when i start the motor, or even just close the hood, it stops working. i thought maybe i had a bad connection, went as far as cutting the plug completly off and butt splicing the wires directly, but same thing. basically if the engine is off, the clutch engages. once i start it, sometimes it works for a while, ( like 3 minutes) but mostly it doesnt work anymore. hot stays hot the whole time. i dont want to spend 300 dollars i really dont have on a new compressor just to find out i still have the same problem. so is there anything im missing here? something i dont know? any help will be greatly appreciated. tell me how to fix it and ill build you a shrine a sacrifice samll furry mammels to you every week cause its a big interior and gets very hot.

This is not something you can fix yourself.A/C systems are complicated and costly to fix.


I’m going to be really blunt . . .

You’re not going to fix this without the wiring diagram for the ac system

don’t worry about the fact it’s a school bus

It’s still an Ford Econoline 350 . . .

Look for the ac wiring diagram for an Econoline 350 with the proper model year and engine

Getting that wiring diagram is a lot less than $300 . . . a Chilton or Haynes would probably be fine in this case. And the problem may very well be electrical nature.

Have you checked all the fuses concerning the ac system?

There should be a separate fuse labeled ac compressor, I would think

Do you even have the owner manual . . . which should have the fuse chart for the vehicle

How are your electrical diagnostic skills?

The reason I’m asking is because of the way you tried to rig the system . . . that’s not something I would have done

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You might be low on refrigerant.

I don’t think it’s a good idea to bypass all the factory wiring for the A/C. The computer will never know when the compressor is on and adjust. Turning on a hot switch will never allow the A/C to automatically turn on and off as required/needed. Most important, unless you know the current draw, high’s and low’s , you might be asking for a nice warm fire if connected to the wrong wire size or fuse.

Get a diagram and use existing wiring. Hey, with that awesome screen name of yours it shouldn’t be that difficult with some patience.