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Another HVAC question…
This is not my motorhome, but my church bus. Our church owns a ’94 H3-45/series 60, 56 passenger bus. Of course, it has over-the-road a/c.
Here’s the problem….the low a/c pressure light comes on with maddening regularity. Any pattern is vague at best, but I’ve been looking at and putting up with it for years…I’m one of about 5 drivers for the bus. When the AC is first used…at the first of a trip, etc….it seems to do well, for a while….not always but most of the time. Into any trip…might be 5 minutes but more likely, 30-45 minutes, the icon warning light will start coming on and stay on an indeterminent length of time. Most of the time, in a few minutes….if you’re lucky… it will go out and, once again, the AC is putting our cold air. When the icon lights up…the vents are not flowing cold air.
A few years back, we replaced the compressor and thought the problem would go to the graveyard with the old compressor, but the same problem quickly reappeared.
I was driving the youth back from Charleston last week (about 4 1/2 hours) and had the AC set where it should have given everybody frost-bite, but it only managed to stay around 77-79 degrees. The AC/low pressue light continuously, and at random, came on and off for virtually the entire trip.
This thing has been looked at by any number of “experts” none of whom have ever managed to whip it. This includes the people we bought the bus from…and they have about 65 Prevosts and their own shop.
Any thoughts, anyone?
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6 Replies
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The low AC press light is activated by the low pressure switch which is mounted in the Freon line.
Any time mine has come on, it has always been low on Refrigerant. Normally due to a leak in the system somewhere.
When the light comes on, it will keep the compressor from coming on when low on Freon.
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Why not add some freon.
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Do you have the dryer with the two floating balls? The tech at Prevost told me both balls should be floating. If the bottom one is not floating, the system is low on freon, which is what it sounds like. We had to replace the suction valve mounted on the compressor a couple of months ago. A qualified tech should be able to pinpoint the leak.
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Per offered a good tip, however the floating ball is in the black receiver tank. That is a quick check on the freon level, not precise, but close enough.
The issue could be a faulty pressure switch but I would also want to see the system pressures when the light is on to make sure it is not associated with something else such as an expansion valve issue.
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There are 2 sight glasses on the side of the black accumulator tank in the condenser compartment. When the system is properly charged, the red ball will be floating in the lower sight glass only.
*Note* don’t hold the door open very long, the condenser is mounted on this compartment door and needs to be closed to have air drawn thru it so as to condense the freon from vapor back into a liquid so as to float the lower red ball in the sight glass of the accumulator.
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Thanks, y’all….I’m on a trip myself, but I’ll pass this info to someone back at home. I appreciate the tips…don’t know why I hadn’t thought to ask before now….what a great resource to have: Prevost Community!!!!
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