Dang, I'm enjoying a few weeks off the road, but not for much longer. I haven't done anything on any projects. So, before I run out of money, I gotta get my bus up to speed. It's got a PS leak, old gold coolant, neither AC works, the heater didn't work, and the blower motor does nothing. Both ACs, the heater, and blower did work (always gotta say that on these auction vehicles).

I'm hoping to get, at least, the factory AC working, and the heater. The aux AC is aftermarket on this bus and I have no info on it - yet. So, on that factory AC...

The compressor doesn't turn on when I have the engine running. When I jump the pressure switch under the hood, nothing happens. When I use my cheapo lightbulb voltage probe to test that harness connector, nothing ever lights up. So, I'm assuming the circuit is broken somewhere? Or a relay/fuse is bad? Or the PCM? is not telling the AC to turn on? I haven't a clue, but I gotta get this fixed.

I've taken my other bus around to a few shops and no one wanted to work on it. My trusted buddy in Dallas, who doesn't do diesels but I hoped might work on my AC, wants no part of it. Two places referred me to the same RV repair shop, and the vibe I got from them was that they were going to just replace every component with new parts. He didn't sound interested in figuring out what was wrong with it. Had a yard full of $500k RVs.

So, I think it's up to me. I'm going to buy one of those power probes y'all recommended, and read the directions, lol. I downloaded AC schematics, but I'm a little confused. I don't see the blower motor anywhere in the schematic. I see an aux blower motor with a switch in the dash, but I believe my bus has rewired that switch to run the back AC. It doesn't have a factory aux/blower. But, I don't see the main blower, the one under the hood.

I'm hoping y'all might look at these schematics and point me to likely places to probe. I've got the diagnostic procedures as well, but circles and arrows would be great. Or, if you know where the blower motor is. I thought the heater issue might be that valve in the heater hose, but I don't see one of those on my bus. Any other ideas? Truck runs fine otherwise. I think all this is electrical. Recall that my key quit engaging the starter to, although none of these other problems coincided with that event.

One more random question - am I messing something up, maybe the starter, by starting the truck with the under hood wire all the time? I notice that the hot wire I'm using to reach the jump post on the battery (original wire doesn't reach that far on Eseries) has slowly burned down all it's copper wires. I'll soon have to strip some more plastic off it to have bare copper again.

 

Ron, that's not enough diagrams for anyone to follow.

 

Thx, Jack. So it not just me. Supposed to be a subset just showing the AC wiring. I'll get another version.

 

Maybe my fault. The second version is for E350-450s "w/o stripped chassis," whatever that means, and it shows the blower motor. I'm trying to imagine why the vans "with stripped chassis" wouldn't have a front blower motor. I'd think they all have that built into the dash.

Anyway, here's a version that shows the blower motor. If anyone could point me to likely places to probe, I'd appreciate it.

If jumping that pressure switch at the accumulator doesn't kick the compressor on, would jumping the relay do it? Not sure which relay that is, but I'll find it. Or, if it didn't work at the switch, will it not work at the relay as well?

 

Geez, I can't imagine why no one wants to work on it. If you wanted to pay the bucks, probably someone who normally repairs ambulances or airport transports would be the most familiar and get it done for the least big bucks.

No start with key - you should upload a diagram for the starting circuit to see if there are related circuits.

Here is a comeback to you. Unfortunately, I only have a 2003 manual, so not sure how relevant, but it might help. I also consolidated what you had.

 

Thanks, Jack. Yeah, my friend in Dallas keeps telling me to take it to the schoolbus yard and ask those guys. But, I'm such a paranoid, with this amazing personality that just attracts and motivates abusers (or that's the paranoia), so I've come to trust very few people. In fact, the guys on this forum comprise a significant percentage of all the people I trust.

While auto AC techs are above home AC repair on my Trusted list, with plenty of others below that, auto electrical techs are even scarier than the AC guys...to me, scarier than the transmission rebuilders. We're always scared of what we don't know. I think there's a boogie repair bill under my bed, his power probe glowing, wires dangling from his claws.

f I can't fix this electrical problem myself, this might become a cool-weather only vehicle.

 

So, I'm running out of time and got to make this truck AC work. I bought a powered circuit tester today, an Innova 5420 for about half of what the Power Probe was. Ever heard of it?

But, I'm flying blind now - lost my access to ProDemand Online where I could get all the diagnostic info on any car. So, I'm starting from scratch.

I checked the fuses and found #13 under the dash was blown. According to something I found online, that fuse controls the AC function selector(s) and blend actuator, which is exactly what I see in the wiring diagrams I downloaded and that one Jack provided. However, my truck doesn't exactly match up with those diagrams. They show two function selectors, front and rear, and two fan switches. My truck has one function selector and two fans. My rear fan switch does operate the fan on the rear Carrier overhead AC in this bus and, I assume, is actually turning the rear AC compressor on since there's no other switch to do that. But I haven't checked under the hood to watch - for all I know, that one AC switch on my dash could trigger both compressors, such that the rear fan switch really is only operating the fan.

But anyway, when I replaced that fuse, my rear AC fan began to work, but not the front fan. I didn't actually start the truck though, so I'm not sure if the rear AC compressor will kick in. If so, I'm good to go - that rear AC cools the whole bus by itself. But, I want to get the front working as well, for winter - recall that the heater quit too.

So, it's all a little confusing. Why would a fuse that protects the blend door and function selector affect the blower motor? Or better, why did it make the rear work and not the front?

I'm thinking that maybe my front blower motor went out. It only has two wires going to it, a red and a yellow. Should I be able to use the power probe to pierce the plastic and energize the wire to power on the fan and confirm it works? Or do I need to have the key on, or ground the other wire, or anything?

Also, this Innova came with no instructions and none on their website. I tried to power that fan with it - easily pierced the plastic and when the tip contacted the wire the probe lit and displayed system voltage But, when I pressed the rocker button on the Innova, nothing happened. Don't know if the blower is bad or I was doing it wrong.

Next, the wiring diagrams show a violet wire coming out of the dash selector switch and going to the "AC Clutch Switch." Where is that? I initially assumed it was the pressure switch on the dryer/accumulator(?) that I jump to trigger the compressor. Then I saw a wire leaving that switch in the diagrams and going to a "Dual Pressure Switch" that I now assume is that connector on the dryer. I'm guessing the AC Clutch Switch is where the wires connect to the AC compressor.

Ditto with a Blower Motor "Resistor." Where is that? It connects to the the blower motor switch on direction and to the blower motor the other way. I can't tell if these are power or ground, or which way the current flows.

 

OK, my front blower motor is bad. Bought a new one, and it was bad out of the box. Should get the replacement installed tomorrow.

 

I have nothing to offer but a pair of not-totally-incompetent hands and a good imagination but I live in DFW and I have a driveway.

If I can help just let me know. Your experience with the 6.0 will be very helpful to me in the future as my own truck is at 225K.

Mark

 

Thank you so much for the offer, Mark. As for my experiences helping anyone - eek, lol. Maybe as the role model for what not to do, lol. But, I'd be glad to try, and I can definitely twist wrenches. I am in Houston though, moving home after 30 years in the DFW area. I still have a couple of vehicles in storage up there and many friends/family.

I felt ill today and didn't work on the truck, but I'm hopeful that fuse might have been the issue. I'll install the new blower motor tomorrow and that should fix that issue. I see that fuse controls the selector switch, which outputs to the AC clutch switch, wherever that is. That clutch switch is also connected to the dual pressure switch, which connects to the PCM.

I can't tell whether any of those connections are power, ground, or ?, but I'm hopeful that somewhere in there I'll get whatever current needs to go to that pressure switch in order for me to jump across it and make the compressor turn. Or, even better, that's the reason it wasn't turning and now it will lock up without me jumping. If I can get the compressor to do something, anything, and it still doesn't work - I can figure it out from there, at least on the front, factory AC, even if I have to replace every component.

And, worst case, I can make do with that front AC - I'd just hang a tarp across the inside of my bus to block off the back end and just cool up front. The rear AC would cool the whole truck by itself, but dang, I don't want to dive into that. It's compressor is buried on the driver's side of the engine, above the PS pump but below a bunch of stuff. I literally can't even see it from under or over. And, I don't know anything about it's condenser/blower unit in back and on the roof.

225 - your block has plenty of life yet. My 450 was running great at 305k, until the thieves messed it up. You'll prolly be replacing a lot of bolt-on parts over the next 50k, and maybe some injectors if they're original. I'll PM you my phone number if you ever need help.

 

Have you ever considered adding a rooftop ac to your bus? I am not sure how involved it would be to get power to it. At least it would be easily accessible to service or just change out the whole unit. There have to be many rooftop units on wrecked vehicles just waiting for a buyer. That is assuming you can even use these while running down the road and not on shore power.

 

Thanks, BB. It has a rooftop AC, that's the second unit. That's why these OEM wiring diagrams aren't accurate - it's all aftermarket. Honestly, I expect it works just fine now that I got it's fan blowing again. I'll find out today. If it works, I'm OK to drive - not comfy though. These Eseries diesels get a lot of heat coming through that doghouse, and with only the rear rooftop AC, I still feel it, and it ain't good, but I can do it. Mostly, I worry about my 15-year old dog, and that rear AC does keep him cool.

 

Well, the new blower motor works fine, and the blend door works fine, and the blower resistor works fine. All fan speeds coming out all front vents now.

But, still no compressor turning. Dang, I can't even see the aux air compressor, but the air coming out isn't cold, so I assume it's not cold either.

First time I started the truck in over a month. Bogged down when I first started it, sounded like it might die but kept going, a little white smoke out the exhaust. Checked codes and had a P0269 and P0620, along with several U-series codes for networks not connecting. Dang, that was Torque Pro, I should have also checked with Forscan.

Another thing - it was just idling in my driveway for 20-30 minutes max and the ECT/EOT got up to 185. Doesn't that seem high for just idling?

 

Frustrating. Found some diagnostic procedures that Sean uploaded long ago. It refers to an AC Cycling Switch - C1081 - and the AC Pressure Cutoff Switch - C1078. The pics of the connector look the same although they're testing voltage on different pins. None of my wiring diagrams include any Cycling Switch, and I know of no other connectors in the system. Here's the pic:




Are these both the same connector and they're just calling it different names? Or, maybe the individual pins in that connector are different "switches"? I'll go check again, but I don't recall there be voltage on more than one pin. What am I missing?

 

I'm hopeless. I can't even tell which way this current is flowing through this diagram. Can anyone explain?

Just checked the voltages on the dual pressure switch connector.

With the key off there's no voltage on any pins. Three of the pins make the green light come on, one (the red/yellow) does nothing.

With the key on, there's only voltage on one pin, the green/orange, and it's 11.7v.

I can't tell what that means. The wiring diagram shows the gr/or coming from the PCM and the relay grounds it.

The procedure says red/yellow should have voltage with the key on, but it doesn't. I can't tell if it supposed to get voltage from the AC clutch switch, or if voltage is supposed to come from the relay.

I pulled the connector on the compressor, then jumped the pressure switch from red/yellow to ground and from the gr/or to ground. With the key on, AC switch on, neither jumper sent voltage to the AC compressor connector. Where does voltage come from going to that connector? It's other wire leads to the function selector, which is on the circuit with that blown fuse I replaced. Wouldn't that be the voltage supply? Yet, the procedures say red/yw comes from the pressure switch and that it's supposed to have voltage.

I'm wondering about my PCM since I have other electrical problems, and since I did swap in the PCM from my ambulance after not getting the PCM connector to lock in on the old one. Maybe it's not a coincidence that the other AC compressor isn't engaging either, and the way it no longer starts with the key.

I have another PCM in my other ambulance I could swap in, but hate to scavenge more parts off it - I need to get it running too.

Any suggestions/answers?

I've swapped relays in the junction box, so I don't think that's it, but maybe I need to check voltages on the sockets for that relay?

I was hoping the AC compressor connector was that AC Cycling Switch they refer to, but it only has two pins, just as it shows in the diagram. One of those pins shows ground all the time, but that other one never shows anything, as stated above.

That AC connector is a PITA to reach, but maybe I can get a wire with an alligator clip on the red/yellow pin, then apply power to that wire with my probe? Should that make the clutch pull in, and if so, confirm that's not the issue?