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When should OTR compressor run?
Hi all,
I got my AC serviced (recharge after hose failure) in Winter Garden and the techs could not answer this question. I have a 96 XL.
AC is working fine when AC is selected on the dash controls. When heat/vent is selected on the dash, we noticed that the AC compressor continues to run. My question is if that is expected or should the compressor only engage when AC is selected? The techs thought it should not run but given the age of my coach, they really didn’t know.
Can someone give me some guidance on how their coaches operate in this capacity? If it shouldn’t run when on heat/vent any ideas on what could cause it to do so? I am guessing a failed relay but no real idea.
Thanks for any advice!!
Mike Harper
2004 Marathon XLII -
21 Replies
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Good question and rather than guess I will send an email to the Prevost experts and post the answer.
I do know mine runs when the temperature selected is calling for heat but not when it is extremely cold. It does modulate the temperature when A/C is called for with coolant through a heat exchanger.
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL -
A VERY good ?. I always assumed mine did not run for heat/vent but I’ve never actually checked. If it runs for heat/vent, it would seem very wasteful in terms of fuel consumption and compressor longevity.
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Mine is an older coach with the O5G Carrier Bus Compressor and think mine kicks in and out like your car. Pulls clutch in as needed. By the way have a Carrier O5G Bus 41CFM that I bought a year or so ago and after checking all mine needed was a seal. Fully loaded with dual belt pulley and clutch on ready to go. Was/is charged with Nitrogen if anybody needs one.
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My 96 (95 chassis) XL 40 only runs 05G compressor when dash switch is in A/C position. Center is off, other position is HEAT which does not operate compressor.
I haven’t been able to determine if compressor “cycles” as do vehicles with CCOT system, as opposed to TXV systems which do not cycle (my experience). My assumption is compressor runs continuously when A/C is selected. Condenser fan on curbside will cycle occasionally.
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Like BGLogistics, my 95 chassis/96 Liberty #331 bus OTR compressor doesn’t come on when the 3 position switch is in the heat position.
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There are different iterations of OTR and their controls so I awaiting a response from Prevost.
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Mike, Prevost needs your VIN to accurately answer your question. If you don’t want to post it email it. My email is activated.
To all others…..this is a strong clue what might be the correct answer for Mike’s coach may nt apply to yours.
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Jon,
Sorry the late response and thanks for your effort. I have to figure out how to get emails when people post as I have to remember to come in and look right now.
Anyway, sent the in email and again thanks for anything you can find out. I was surprised that the Prevost shop couldn’t find out.
Mike
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See my response in an email. I can forward Robert Hitt’s full response if needed. It is very detailed and long.
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Jon or Mike is that info something you would share? I’m interested in Prevost’s response also.
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Don’t know the answer to the question, but some systems in automotive use run the compressor any time the system is on for AC or heat to provide dry air to the defroster system to make it more efficient.
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL -
What John said is correct, but some vintage Prevost coaches have a switch to select heat or A/C. On those the compressor is not running unless A/C is selected.
Prevost suggests having it on, even when heat is called for to keep the windows from fogging.
Newer Prevost coaches have the compressor running all the time.
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Yes I’m familiar with automotive systems engaging compressor for defrost/defog. That has been common for probably 30 years or so and does do an effective job keeping humidity low in interior and windows clear.
And I have manually done the same in the bus (turning on A/C) to defog the windshield while temp was set to warm side.
Jon when you said Prevost’s response was very long and detailed, call me a nerd but I was interested in that mostly what changes/differences in system they had or used throughout the years.
Not trying to be a PIA. Just curious. Part of the reason for that is after I bought coach in Dec 18, OTR compressor shaft seal was leaking/throwing oil. Bought the seal from Prevost and had a charter bus shop replace shaft seal, change compressor oil and add about 4lbs 134A refrigerant. Ran at fast idle in shop for 1-2 hrs no issues great coooing. Shop did tell me compressor had more shaft end-play than he likes to see, and not to be suprised if in a year or so it’s leaking again. That happened on the 2 hour drive home, however since then it seems to have nearly stopped. In any case, I saw the 05G listed for sale above. What I don’t know is if there were any differences in those as far as cycling clutch vs non-cycling clutch, and if so may not be any difference in compressors anyway. Also are they the same for R12 vs R134A (which I have). Maybe I read too much into Jon’s reply but I thought there was a chance some answers might be there when “long and detailed” was mentioned. Thanks.
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Prevost makes running changes so for answers in some cases to be accurate the VIN may be required which is why I am reluctant to post information specific to a particular production range.
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Then I think you should post that this is applicable for 1996-1999 Prevost’s coaches by these converters. :). But it would be good to have that information available for people to know. 🙂
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