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Old 05-16-2019, 12:42 PM   #1
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Air Conditioning Problems

2017 Montana 3730FL.
We're in Austin TX. Weather is starting to get warm. The AC's aren't keeping the rig cool. It's only 83 out, both AC's have been running all day but can't get inside temp below 78.
The air comming out the ductwork is in the low 50's. Seems like the rig should cool down but it's not.
Anyone have any ideas?

Bill
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Old 05-16-2019, 01:00 PM   #2
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Are both AC's feeding the same duck work, is the air volume ok, are filters clean. Low refrig. coolant can cause poor cooling but both having the same issue might rule out that problem. I'd like to see temps in the 30's/40's coming out the duct work.

CLIFFORD
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Old 05-16-2019, 01:18 PM   #3
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Quote:
Originally Posted by clifford j View Post
Are both AC's feeding the same duck work, is the air volume ok, are filters clean. Low refrig. coolant can cause poor cooling but both having the same issue might rule out that problem. I'd like to see temps in the 30's/40's coming out the duct work.

CLIFFORD
In this system, both ac's feed the same ducts. I cleaned the filters this morning.
Bill
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Old 05-16-2019, 01:43 PM   #4
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If you have a return air temp of 78 and a supply air temp of 54... that is good. A 24 degree differential is very good.

Mine does the same thing sitting in the sun. If you find a miracle cure, please let us all know.
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Old 05-16-2019, 01:48 PM   #5
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id be very disappointed. but this is common prob for entry level units. tint the windows. window awnings on every window. patio awning out.

last resort trade it in for used rig of better quality. 87 outside in OK and its 70 in here.
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Old 05-16-2019, 01:59 PM   #6
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In this system, both ac's feed the same ducts. I cleaned the filters this morning.
Bill

Assuming (from the pics) your duct output temp is 54, your outside temp is 82, and your inside temp is 77.
Correct operation of A/C is measured using the Delta between A/C intake temp and the A/C output. Dometic and others spec that Delta as about 20 - 23 degrees. In your case, that means 77 minus 54. That's 23 degrees and well within spec. That also means the only way to get a lower inside temp is to reduce loss of cold to the outside or reduce gain of heat to the inside. Typically, the easiest method is to add insulation to the windows, park in the shade, shade the windows with awnings, change direction of the vehicle to reduce sun exposure, or all of these.
You have bumped up against the "need another A/C unit" or "need more insulation".
To put it another way, you are gaining heat as fast as you are cooling. The A/Cs are working at capacity .... you need to reduce the gain of heat. The 30s/40s mentioned by another poster is not possible unless the inside temp was 53-63 degrees (the Delta of 23).
Using your IR gun, look for hotspots ... windows, walls, entry door, etc. Very small changes can make a big difference.
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Old 05-16-2019, 02:04 PM   #7
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78 and 54 your A/C 's are working just great. They can not do any more. 20 degree differential is by design. Close curtains. Tint windows.
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Old 05-16-2019, 02:24 PM   #8
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Quote:
Originally Posted by bruceisla View Post
Assuming (from the pics) your duct output temp is 54, your outside temp is 82, and your inside temp is 77.
Correct operation of A/C is measured using the Delta between A/C intake temp and the A/C output. Dometic and others spec that Delta as about 20 - 23 degrees. In your case, that means 77 minus 54. That's 23 degrees and well within spec. That also means the only way to get a lower inside temp is to reduce loss of cold to the outside or reduce gain of heat to the inside. Typically, the easiest method is to add insulation to the windows, park in the shade, shade the windows with awnings, change direction of the vehicle to reduce sun exposure, or all of these.
You have bumped up against the "need another A/C unit" or "need more insulation".
To put it another way, you are gaining heat as fast as you are cooling. The A/Cs are working at capacity .... you need to reduce the gain of heat. The 30s/40s mentioned by another poster is not possible unless the inside temp was 53-63 degrees (the Delta of 23).
Using your IR gun, look for hotspots ... windows, walls, entry door, etc. Very small changes can make a big difference.
I understand the 20 rule. But right now it's only 82 outside but 79 inside. Surely two ac's should lower the temp inside more than 3. I might as well open the windows and turn the AC off!
Bill
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Old 05-16-2019, 02:32 PM   #9
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Originally Posted by consolenut View Post
id be very disappointed. but this is common prob for entry level units. tint the windows. window awnings on every window. patio awning out.

last resort trade it in for used rig of better quality. 87 outside in OK and its 70 in here.
Entry level unit? I didn't realize a Montana was entry level.
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Old 05-16-2019, 02:40 PM   #10
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Entry level unit? I didn't realize a Montana was entry level.
It's not. As others have mentioned, if you are parked in the sun and or don't have the windows covered, you are not going to get too cool. Also having dual pane tinted windows helps a lot. Good luck.
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Old 05-16-2019, 02:42 PM   #11
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......but this is common prob for entry level units.
Montana is an entry level 5th wheel? Where do you get your information from?
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Old 05-16-2019, 02:46 PM   #12
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I understand the 20 rule. But right now it's only 82 outside but 79 inside. Surely two ac's should lower the temp inside more than 3. I might as well open the windows and turn the AC off!
Bill

Well ... I think your question should be:
If the 2 A/C units are outputting 54 degrees, why can't the inside temp drop below 79 degrees? The answer has to be your are losing the cool air to the outside or you are gaining massive amounts of heat, or both. Stop the heat gain ... really .... it's just like a parked car ... block the sun! BTW, check your outside wall surfaces with your IR gun .... bet they are much hotter than 82 !!
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Old 05-16-2019, 02:52 PM   #13
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Old 05-16-2019, 03:03 PM   #14
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Quote:
Originally Posted by bruceisla View Post
Well ... I think your question should be:
If the 2 A/C units are outputting 54 degrees, why can't the inside temp drop below 79 degrees? The answer has to be your are losing the cool air to the outside or you are gaining massive amounts of heat, or both. Stop the heat gain ... really .... it's just like a parked car ... block the sun! BTW, check your outside wall surfaces with your IR gun .... bet they are much hotter than 82 !!
The outside wall with the sun on it is 130. That same wall inside is 88.
Bill
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