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Old 11-05-2008, 12:02 PM   #1
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a/c testing how-to

Sorry folks if this has been covered before, I couldn't find it mentioned. I need to know just how to test my ac in place before I bite the bullet and take it in. If I can see if it works, then I need to know what to do to maintain it. Such as blowing out with air or washing it out with a hose or leaving that to those who should know better.

I can't seem to find a thermostat, just the buttons on the unit itself. It also has the heat strip. Needs to be tested as well. The unit is a coleman and I would think it to be the original at 1976.

In additrion, will I need a generator that puts out a minimum of a true 2kw to perform this test?

Thanks in advance to all....Dan
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Old 11-05-2008, 01:43 PM   #2
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It's almost too cold now to get a good test on an AC. The thermostat should be with the buttons on the front of the unit. It may be a slide bar or may just have setting using the buttons.

You want at least a 2500 watt generator. Generator are generally rated much higher than they can provide when a starting load is applied.

You should be able to test the heat strip in these temperatures and test air flow at the same time. If you get a good strong air flow the unit should not need any level of cleaning. This type of AC seldom needs coil cleaning.

If you do run the AC remove the cover at the ceiling and reach up and feel the cooling coil while the AC is running. It should feel COLD. If you can test it on a rainy day with the trailer opened up to allow outside air and humidity in the trailer you should see condensate forming on the coils.
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Old 11-05-2008, 02:53 PM   #3
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Dude, that unit is over thirty years old! Get the Dometic low profile. You will have to get
the pan from Inland. There is a "Airstream" cowl for those; maybe Andy & Terry have that, as well.
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Old 11-05-2008, 03:41 PM   #4
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Maybe, maybe not

Quote:
Originally Posted by Mike Leary View Post
Dude, that unit is over thirty years old! Get the Dometic low profile. ...
Don't assume the original unit is still installed. Howie gave good advice; karma to him.

My advice, in cold weather, is to turn the propane furnace on AND switch the air conditioner on at the same time.

If the AC pumps out cold air while battling the heat load then stop troubleshooting.

Tom
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Old 11-05-2008, 04:01 PM   #5
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As far as I know, the Coleman was the only ac installed in, at least, mo/hos? Old ac units look dorky.
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Old 11-05-2008, 04:04 PM   #6
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Quote:
Originally Posted by HowieE View Post
It's almost too cold now to get a good test on an AC. The thermostat should be with the buttons on the front of the unit. It may be a slide bar or may just have setting using the buttons.

You want at least a 2500 watt generator. Generator are generally rated much higher than they can provide when a starting load is applied.

You should be able to test the heat strip in these temperatures and test air flow at the same time. If you get a good strong air flow the unit should not need any level of cleaning. This type of AC seldom needs coil cleaning.

If you do run the AC remove the cover at the ceiling and reach up and feel the cooling coil while the AC is running. It should feel COLD. If you can test it on a rainy day with the trailer opened up to allow outside air and humidity in the trailer you should see condensate forming on the coils.
Some nice thoughts, but unfortunately, they are not totally on the mark.

First, a Yamaha EF2400iS will start and run a 13.5 K roof unit. I can't vouch for any others unless they are at least 3000 watts running.

TomW's advice about heating the inside of the trailer is a good one, but the will probably not operate below 50* outside ambient temp anyway, but worth a shot.

I have found that keeping the coils clean is an almost yearly maintenance task on many of the units that I service, so I would definitely look at the condenser and evaporator coils and clean them with a commercially available coil cleaner before you do your testing.

Testing for 'cold' is not an acceptable performance test for a roof air unit. You should be testing the difference between the return air temps (measured at the return air inlet to the unit) and the exhaust air temp measured at the air distribution box. There should be an 18*-22* difference between the two measurements. If you are not getting this difference and it is below 18*, your unit is not operating to the specifications and may be in need of a re-charge of refrigerant (only if there are provisions for this on the unit. New Roof A/C units DO NOT GET RE-CHARGED, but rather get replaced if the refrigerant level is below spec.). Further, if you are getting low temp differentials, there is a very specific way of testing the amp draw of the compressor when running to determine the state of refrigerant charge with-in.

There are no such performance tests for heat strips, and they generally do not produce a lot of heat as these elements are typically in the 500 watt range and work best on low fan speed.

Hope this helps.
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Old 11-05-2008, 04:30 PM   #7
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Some nice thoughts, but unfortunately, they are not totally on the mark. they generally do not produce a lot of heat as these elements are typically in the 500 watt range and work best on low fan speed.
They only work on one fan speed and are very nice to heat up in the morning.
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Old 11-05-2008, 08:58 PM   #8
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Hey strmstr69, I've got the MH owners manual in hand. It has trouble shooting charts for cool & heat. I'd post it here but it's 22 pgs long. PM me with your e-mail & I'll send it over to ya. FWIW I've got Super Mach Coleman A/C with heat
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