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Dash Air 1999 XL Featherlite
Can anyone tell me what the function of these pressure switches on my dash air,they are after the compressor just before the air dryer. Installed new compressor,dryer, and expansion valve and refilled with 134a but will only cool to 63 degrees,see next post for pics.
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12 Replies
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Low pressure and high pressure sensors. If 63 what was the differential. I have new compressor, dryer and expansion valve as well and the best we got was 59 with ambient being close to 80.
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Thanks Tom for the reply.That was the actual temperature blowing out the dash vents the outside temperature at the time was about 85 degrees so 63 degrees at the dash is not cold enough to cool things off.It used to blow at 50 degrees but can’t seem to get it down there now.
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Temperature Differential??
Isn’t a 20 degree temperature
differential between the between the intake air and and the cooled
air coming out of the evaporator about right? That’s has been my
understanding for a long time.80 degree air going into the evaporator
should be about 60 degrees coming out.75 degree air going into the evaporator
should be about 55 degrees coming out.You get the idea.
As the coach gets cooled the intake air
gets cooler and cooler as does the air coming out. Systems with any
more temperature differential are more likely to have ice form on the
evaporator coils.Maybe some AC experts will chime in.
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Yes, I think 20 is good. I do compare the intake and output, I should have been more clear. If I see 20 that’s really good, mine is usually in the high teens.
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It doesn’t seem very cold at that differential so do you find it cools ok we find it doesn’t really cool that good.
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One factor to consider is if the system is on recirc of inside air or if the system pulls in outside air.
Trying to cool hot outside air by 20°F could be more difficult than a gradually cooling of recirculating inside air. The outside air never gets cooler so the 20° delta stays the same. Dropping cooler inside air by 20° eventually gets much better.
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One other item to check is the low-pressure bypass valve. It is in the picture above at the bottom left center. It has the copper tubing going in and out from it. It is used to prevent the system from cycling on the low pressure side by allowing hi-side gas to be inserted into the low side line to prevent this low pressure cycling. This device was added long ago due to the long a/c lines in the dash a/c system. It is normally set to begin allowing high side refrigerant into the low side line when the low side pressure get around 28-30 psi. If for some reason the valve is not closing properly or is opening too soon you keep the low side pressure too high and the system does not cool as effectively.
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Thank you we will check that out.
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would prevost have this valve?
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They should have them as they began to use them again on the motor home shells a few years ago because of a change in expansion valves.
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I have ordered from Prevost and it is on its way thanks again.
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changed the pressure valve and system works great blows at 47degrees thanks again for the tip.
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