[Bernie]

If the compressor is running the fans should be operating.

[Archived]

My 95 chassis condenser fan will occasionally cycle on/off if A/C is turned on in shop when temp is fairly cool outside. Also in same scenario there is a delay before condenser fan starts after turning on compressor. When outside temp is high I haven’t noticed that other than the initial (shorter) delay on fan starting.

[Archived]

Mine come on shortly after turning on a/c and I have never heard them cycle. I have had trouble with my condenser fan relay, the large one located in my condenser fan compartment.

[ed]

My evaporator and condenser fans never cycle when ac is selected unless R38 and/or R39 solenoids are going bad. Here are 2 threads on the subject

http://www.prevostcommunity.com/forum/threaddetails.asp?Category=HVAC&ThreadID=5674

http://www.prevostcommunity.com/forum/threaddetails.asp?Category=HVAC%3E&ThreadID=6464#59691

[Towson]

I think that’s my problem because mine work whenever they like, if I just the power at the relay no issues they run all day, so I have ordered a relay to replace the one on there and hopefully that resolves the issue

[rafael]

Oh so I changed out the condenser fan relay and still a no go after further inspection what my problem seems to be is that the signal wire that tells the relay to close and open has no power, meaning what ever tells it to turn on is not working, if I put power to that signal wire the relay clicks and fans come on. Question is what tells that relay to activate or deactivate? Is it a sensor in the compressor or cooling system? Is it the dash control?

[Jeff]

If you turn the OTR ac switch on and the clutch on the compressor does NOT engage, and the fans don’t come on, my bet is you are low on freon, or the low pressure safety switch is bad. The switch could be bad too. There are safety switches on both the compressor and the accumulator.

[Archived]

Compressor comes on the fans do not, I installed new relay and same issue I then checked further and my issue is what ever tells the relay to turn on is not working the little signal wire has no power I just don’t know where that signal comes from.

[Chuck & Katrina]

Well found the source of my problem, turns out the pressure switches by the compressor on that aluminum block are bad and have failed there is a low fan speed switch and a high fan speed switch and both have failed, prevost has them in stock for $70 each. So just an fyi preventative maintenance for you folks out there don’t want to get left out there with no ac for a pressure switch.

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2000 Featherlite H3-45

2024 Jeep Grand Cherokee

Leesburg, FL

[Ron]

I’m not sure what you’re talking about?

Pictures speak a thousand words.

[Archived]

These

[Jack]

The Prevost OTR ac system(R134a) on my bus doesn’t have that aluminum manifold. Maybe what you have is an H chassis thing? or Featherlite thing? or a change Prevost made for your later model?

My XL has at least 6 pressure switches. On top of the compressor there’s a brass fitting with 3 low pressure switches, and another brass fitting with 2 high pressure switches. On my bus, there’s one other pressure switch on the side of the receiver/accumulator tank. Some buses have 2 switches on the receiver/accumulator.

Of the 5 switches located at the compressor, 3 are for controlling the unloader valves, and the other 2 protect the compressor from damage by way of clutch disengagement in case pressure gets of too high or low.

I looked in the PrevostCar online technical publications, parts manual, for my unit#, which led me to parts manual# PA-1189, to find the above mentioned compressor pressure switches for my bus. These compressor switches are on pages 2117 & 2118 of this 2426 page pdf file. The receiver/accumulator switches are on pages 2199 and 2200.

The switch(es) on the receiver/accumulator control the condensor fan(s). 40 foot buses have one pressure switch for 1 pair of fans. 45 footers have two pressure switches that control 2 pairs of fans at different pressures from each other.

In a last ditch effort to protect the ac system, there is a pressure relief valve on the receiver/accumulator that opens at 450 psi.

How the OTR system works and is protected can be found in the PrevostCar online technical publications, technical manuals, for my unit#, which led me to maintenance manual# PA-1082. I found the above info on pages 393 & 394 of this 466 page pdf file.

As always, your results may vary.

[rafael]

I don’t have that aluminum manifold either. Mine looks like Don’s other than his compressor is clean – where mine is dirty oily due to a shaft seal leak. Only other difference is that my condenser fan will cycle at lower ambient temps. Haven’t looked at accumulator to see how many pressure switches are there. Can’t get the door open without moving some things.

I went thru the online parts manual page by page shortly after buying bus. Printed all pages that were specific to my VIN range. Couple hours a day for a few weeks – suprised the printer survived. Throughout all that, there were a few things that didn’t match my XL40 MTH, however did match XL45 ENT. Adding to that, on the electrical diagram inside LR engine door, on the bottom of that diagram is printed XL40MTH/XL45ENT.

[Frank]

Guess it an H thing or Featherlite but also fun fact that stainless line that feeds the aluminum manifold has a screen filter at the other end of it which in mine was clogged up not allowing Freon to flow to that aluminum manifold which turned out to be my issue, since Freon wasn’t flowing the switches where not reading the pressures and not turning on the fans. We guess now I don’t have to worry about the relay and the switches for a while and if they do go bad I have some spares lol.

[Chris]

Billy, If your bus is like mine, that single pressure switch on the receiver/accumulator opens the condenser fan circuit when/if pressure drops to 90 psi . When pressure climbs back up to 120 psi the circuit closes and the condensor fan runs again. This will happen in low ambient temps with the 3 position AC/OFF/HEAT dash switch in the AC position.