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Old 07-26-2014, 12:32 PM   #1
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dash air not cold enough

i have a 2004 38 foot alpine that the dash air will not get cold enough. when i purchased the unit the dash a/c would not cool at all. the system had a leak at the compressor clutch so i replaced compressor, dryer and expansion valve and pulled a vacuum on the system and charged. when the out side temp is 95 or more the dash air struggles to blow 60 degrees. when the out side temperature is 80 or less i have seen 40 degree at the vent. is this normal for an RV, or do i have another problem. oh ya i failed to mention i checked my heater valve and it does shut off which keeps the hot water from circulating through the air box. maybe this is normal but all of my cars blow 40 degrees.
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Old 07-26-2014, 01:37 PM   #2
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The reality is this, an A/C system is considered to be working properly when it blows 30 degrees cooler that outside ambient temp.

I just serviced my A/C as well, and have come to the conclusion that the Generator and the house A/C's running is more comfortable and more economical.

Besides, at those temps ( 90+), unless you install a divider panel just behind the front seats, the dash A/C has no chance of keeping up! Too much volume inside the coach.

BTW are you measuring temp at idle speed or 1500-2000 rpm?
What kind of pressures are you seeing (h & l).
how long ago did you make these repairs?
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Old 07-26-2014, 02:20 PM   #3
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On my '04 I get better performance from the dash air if I use the MAX setting, recirculating the air inside the coach instead of pulling in hot outside air. My dash air does a decent job of keeping us cool until the outside temps get above around 95. Above that we often run the generator and the roof air to keep the coach to a livable temperature. And the rest of the coach is comfortable whenever we stop for lunch, etc.

A 36' RV (or 38' in your case) is a lot for the dash air to keep cool all by itself, especially if the sun is beating in that big windshield. Usually all we need is cool moving air hitting us in the driver and passenger seats to keep us comfortable on the road.
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Old 07-26-2014, 02:22 PM   #4
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Not sure what the exact physics are but the differential between [inside] ambient air and the A/C vent can only be about 20-25 degrees. By comparison, your car has a relatively small amount of ambient air [by volume] to cool while the dash air in a coach has the entire coach to deal with--the heat load sitting in direct sun shine is enormous. Generally, the dash air will work ok in the 70s and 80s but struggles above 90, unless you use the divider curtain behind the driver/pass seats to help limit the volume of air the dash is air is trying to "condition"......Ref a number of posts on the forum, I believe the 04 has an electronic engine fan controller vs the mechanical wax valve so fan speed should not be an issue for you.
Ditto on using the "max air" setting to recirc inside air vs bringing outside air in.....
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Old 07-26-2014, 02:43 PM   #5
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Quote:
Originally Posted by Jim A View Post
On my '04 I get better performance from the dash air if I use the MAX setting, recirculating the air inside the coach instead of pulling in hot outside air. My dash air does a decent job of keeping us cool until the outside temps get above around 95. Above that we often run the generator and the roof air to keep the coach to a livable temperature. And the rest of the coach is comfortable whenever we stop for lunch, etc.

A 36' RV (or 38' in your case) is a lot for the dash air to keep cool all by itself, especially if the sun is beating in that big windshield. Usually all we need is cool moving air hitting us in the driver and passenger seats to keep us comfortable on the road.
When the outside air is 85+, we use the dash air on max setting(coach&towed vehicle and it does not fail to keep the coach very comfortable about 6-8 ft back. We also run the overhead defrost fans on low to help circulate the air. Above 85 degrees, the genie comes on and the front a/c. If the ambient temp stays in the 90s, we fire up the rear coach a/c also. The vent temps of our dash a/c have always registered in the low 40s. Anything higher than 50+ would denote a problem to me.
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Old 07-26-2014, 04:13 PM   #6
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I usually start the generator and run the roof AC units. To do this I turn off the engine. Start the gen. Turn off the Zantrex charger. Restart the engine. This procedure is to prevent the gen from shutting down when the engine and gen are running. Many other posts on this.
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Old 07-26-2014, 05:18 PM   #7
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Quote:
Originally Posted by krob911 View Post
i have a 2004 38 foot alpine that the dash air will not get cold enough. when i purchased the unit the dash a/c would not cool at all. the system had a leak at the compressor clutch so i replaced compressor, dryer and expansion valve and pulled a vacuum on the system and charged. when the out side temp is 95 or more the dash air struggles to blow 60 degrees. when the out side temperature is 80 or less i have seen 40 degree at the vent. is this normal for an RV, or do i have another problem. oh ya i failed to mention i checked my heater valve and it does shut off which keeps the hot water from circulating through the air box. maybe this is normal but all of my cars blow 40 degrees.
I think there are 2 questions here. First, is your a/c working as designed? If you have put gauges on the system and confirmed you are correctly charged with freon, then it is WAD. Second, is it cold enough for you? I think all the previous comments have covered this. If the curtain and recirculating the air doesn't work, then the roof a/c is the only solution.
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Old 07-26-2014, 05:34 PM   #8
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What I have found here in the desert southwest is if it's near 100 or so, the dash air will get progressively warmer the longer we drive at interstate speeds. I believe the refrigerant lines pick up heat in the length of the coach, therefore reducing the cooling. It cools off immediately when rolling through towns or construction zones. Probably just poorly insulated lines........ JB
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Old 07-26-2014, 07:18 PM   #9
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All - No one mentioned freezing up of the dash a/c, and it would under certain conditions. It happened to us once in CA coming out of AZ on our way bay home to WA state. Pulled over and check to see if it was in fact freezing up. It was, turned on the fan only for 45 minutes and then it was fine the rest of the way home. Check that and see if this is the problem. Normally the Delta T Split on an RV dash A/C system is 20-25 degrees less than outside air, and that is if it's not 90+ degrees outside. There is no way the dash a/c can keep the whole coach cool, does not have enough power and was never designed to do that anyway, you need coach cool, start the genset, once it takes over coach load, disable the charger and then start the main engine and genset can run together. Then you can use both roof a/c's. They have enough to keep the coach at least 20 or so degrees cooler than outside, but they won't keep it 70 if it is 100 outside.

You had a leak, I hope you vacuumed it down for at least 4 hours before you recharged it, because it takes that long to get all the moisture and atmospheric air from the system. The amount of refrigerant and oil that must go back into the system is on a data plate on the compressor, since you changed that, use the new data for the new unit.
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