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OTR AC COMPRESSOR OIL LEVEL
Looked for an article…can’t find. As an owner of 3 Liberty’s, I can’t believe Jon hasn’t written one on OTR service and recharging.
Seriously, I recharge my OTR every June or so; seems like it takes 2-3 pounds or so. Been doing this for a few years and thought I’d take a look at compressor oil level as someone told me you lose some oil with freon loss and the oil should be replenished. My OTR manual says sight glass on compressor should show about 1/2 full and oil level should be raised or lowered through the fill plug.
1. My sight glass appears to be completely full of oil with compressor not running. Am I correct in assuming this level should be checked with a/c off?
2. Can’t find fill plug. Can anyone help with picture or diagram.
Talking about a 1999 XLV chassis.
1999 XLV X-6872, liberty #440 -
18 Replies
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There is an oil fill plug just above and off to the side (slightly ) of the sight glass. The Link below shows it.
Both Prevost and Carrier have excellent instructions of their respective manuals for the AC system and would be far better than anything I could write. I suspect you are OK with respect to oil level, but it should be 1/2 way up the sight glass. Too much overfull is not good. Oil level is checked with the unit not operating.
http://www.manualslib.com/manual/806808/Carrier-05g-Twin-Port.html?page=10#manual
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Thanks, got it. My compressor has a sight glass on the curb side and another sight glass with fill plug on the road side.
Oil level appeared to be high in both sight glasses, so I cleaned the area around the fill plug and cracked it loose. Greeted by the escape of a mixture of high pressure gas and oil. Let it hiss for a minute or two thinking it would stop but… Closed the fill plug.
Anyone know what’s going on? I’m guessing there may be something wrong internally allowing freon to leak by the compressor pistons/rings and pressurize the compressor crankcase or should I just let it hiss away for as long as it takes to depressurize? The OTR is functioning normally at this time.
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Leave it alone if you don’t have a vacuum pump, you have to valve the compressor off to open the fill plug, if not you will lose all your freon and let mositure in. Darrell
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Joel, the reason for the pressure is the piston rings are not a perfect seal and the pressure of freon in the system is also pressurizing the crankcase. Darrel is correct.
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AHA Well, there’s definitely plenty of oil in the compressor; I guess I’ll just top off freon as usual.
Is there any way the oil level (fluid level) in the compressor could be rising?
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No. If anything it goes down as freon leaks from the system, that is why around all leak points you see that black oily residue. Typically the greatest amount is behind the clutch, but since the system has multiple connections and devices you caould see traces of oil everywhere.
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Joel Where is the level with it running for 5 to 10 min? Back when I had 3 coach’s [ 2 Liberty’s 1 Marathon] with road air I would change oil in the compressors every 2 years
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That’s what I was told…I should check oil level if adding 2-3 # freon/year for several years.
Don’t know where the level is when running but I can check when I top off freon in a few days.
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Curious, what kind of oil these take??
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P O E oil for 134a Joel Don’t foreget to purge your freon hose first
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Thanks Darrell. Need to add some to my 134 system ( it was changed over from R12 years ago) and have seen where if the rings don’t seal will have pressure in bottom of compressor at oil fill plug. Can’t see where you would lose all freon if just adding oil unless rings are leaking by big time. If I do , I have a dual stage Robinaire vaccum pump i use of the other vehicles out here.
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You will lose a lot of freon if you don’t block off the compressor and you cannot put oil in if freon is rushing out.
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If you remove the plug without back seating the compressor valves you will loose all of the freon. Stop and think about it, if you loose freon there is oil there at the leak.
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When we speak of back seating the compressor valves, are we talking about the valves, one by the low side schrader and one by the high side schrader that have a square stud sticking up under a plastic cover that takes a 3/16 open end wrench? If yes these are always back seated except when vacuuming or charging. Prevost manual says 3.5 turns clockwise to open.
We have one site glass on curb side. Looks like it is over full as there is no oil line visible, or its empty and we are seeing residue staining the glass.
I too have been trying to find a leak the past couple seasons after seven no problem seasons. Finally bot a leak detector kit, and it found the leak in the -20(20/16″) aeroquip hose that runs from the condenser bay to the evaporator bay, one inch ID, 1.5″ OD. The leak is in the pores of the hose not at a fitting. Got the last one out of New Jersey, and going to Prevost Quebec next week seeking the genius on this system.
When I vacuum to 29 inches of mercury (HG), does this remove the oil?
From the vacuum state, does charging with 24 pounds of 134A put oil into the system?
Or do we need to add oil separate from the freon?
Since we have a drain and fill plug near the bottom of the compressor case, it infers that oil may be added separate from freon? -
Don I chased a leak on my last Liberty 3 or 4 mouths, condensor hose was leaking behind the spiral wrap, the fittings on the hose or reuseable they screw on & off, I gave Jon 2 pcs of hose last year at Bella Terra
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