OK, I've always had electrical issues; but now, my bus does too. Last trip, my ACs quit working but it wasn't a big deal because the weather was nice. I expect warmer climes for my next run across the CA desert, maybe both ways. So, I pull out my gauges, the ones I don't trust because they won't hold a vacuum, and immediately find a bad o-ring, so may have fixed them.

With the engine off, both gauges were around 100. When I start it up, I can't get the compressor clutch to kick in. I crawl underneath and am able to easily turn the clutch by hand, no resistance at all. So, I go back up top, find the pressure switch, make a jumper, and try to get the compressor to turn on after starting the engine back up. Nothing. Tried all combinations of the 4 pins in the connector.

I ran out of time, but I'm assuming this means I'm not getting any juice to the compressor - i.e. some electrical issue, i.e. I'm screwed.

Back up: I've had issues with the bus since I bought it a few months ago. The dash lights have never come on and the front fan hasn't worked. I haven't had a need for the AC, so hadn't really tried the front unit. I have turned on the rear AC (completely separate systems) and it worked great (big roof mount unit), so I wasn't worried - it cools down the whole truck by itself.. The heater works, but without a fan it's kinda weak. There is a 12v (I assume) aux heater in the back with a dash switch that works, but not very well.

As well, the day I bought, you may recall, I had to replace an injector, and when I finished, the key quit working the starter. I get the PATS alert on the dash every time I start it up, but I don't think it has a PATS system (and I read that was normal). On second thought, I can't swear the dash lights/fan didn't work before the key quit; I never tried to use them in the brief drive before it broke down.

But, I definitely know the rear AC was working, and when it worked, I can't explain why, cool air would come out of the front vents as well if I set those on Vent (cooler than outside air, although not as cold as AC air). But, on the last trip, the rear AC quit working, although it's fan still works.

If I can just get one of the two to work, I'll be good for this next trip. So, I first tried to just add some freon to the rear AC (at least see what the gauge said), since it had just been working. Those connections are under the truck in lines running from the engine compartment to that rear roof mount unit. It wouldn't take any freon at all. I assume because the compressor wasn't pumping. FYI, on the Eseries, that second, rear air compressor is on the driver's side, above the power steering, below the exhaust manifold, behind a vacuum pump, obscured by the air box and CAC tube, and covered up by the gas lines running to it. I am totally serious - I did not even know these had a second compressor until this bus, and this is my third E450 with the dual AC set up, they're that hard to see.

Well, I don't have a clue where the pressure switch is for that compressor, or the relay, or the fuses since they're all aftermarket and hidden. NOTE: I have checked every fuse I could find, by (pardon my electrical stupidity) using one of those circuit tester lights with the alligator clip and metal probe. I touched it to both contacts on each side of the fuses and every fuse, every contact, made the light come on. That was disappointing - thought I'd at least find the dash lights and fan issues.

I should add that there's a rat's nest under the dash with additional wiring added for a wheel chair lift, high idle system (both inoperable), and Telma electric driveline brake system.

So, I moved on to the front, OEM AC system, which is where I'm stuck now. How can I make that compressor kick on? I bet it blows cold if I can just get the compressor to turn. What would stop it from working if the clutch seems to spin (or am I doing that wrong?) and the pressure switch is jumped? Could it just be the clutch completely shot? If so, wouldn't I hear it trying to kick in? The low side pressure does go up and down, like it does when a compressor is turning on and off, but I confirmed that the compressor is not turning when it does that.

I was going to take the clutch plate off any way to see, and I don't know what brand compressor this is, but it doesn't look typical. First, the center bolt is tiny, smaller than the 5/16 socket I tried. And there's a raised lip around the outside circumference, which makes it impossible to jam a bar/screwdriver across the other bolts to hold the clutch while you break the center nut. And those bolts wouldn't hold even if you could reach them. They have a smooth round head, more like a rivet than a bolt head. I don't know how one would hold that clutch in order to get that bolt out, although it's possible that such a tiny bolt isn't hard to break.

Is it possible that my electrical is all working fine, and it's just that the clutch is completely shot and that's why it doesn't turn when the pressure switch is jumped?

 

Here's a link to a compressor with a clutch that looks like mine. How do I get that off?