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Old 06-26-2013, 04:53 PM   #1
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Roof air issues

98 monaco diplomat with 2 Duo therm roof air units they have trouble keeping cabin cool seems like it does not blow air very fast of cold even with the thermostat on high? Is my thermostat bad or need replaced, on my last older RV the roof air worked great.

Thanks in advance!

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Old 06-26-2013, 05:00 PM   #2
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Hi Ohorn,
Consider the next step is to have a technician do a test on the air temp going into the unit and the temp coming out of the unit. Depending on the results, it will determine how you proceed.

If the main concern is between 3-8 PM and you are in summer heat, it may be what you have is the best you are going to get. If the coach is facing west, consider covering the windshield.

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Old 06-26-2013, 05:06 PM   #3
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Originally Posted by Ohorn View Post
98 monaco diplomat with 2 Duo therm roof air units they have trouble keeping cabin cool seems like it does not blow air very fast of cold even with the thermostat on high? Is my thermostat bad or need replaced, on my last older RV the roof air worked great.

Thanks in advance!
Before you throw any money at it get an Infrared thermometer gun and check actual temps at the inlets, outlets, and interior surfaces of the RV. The rule of thumb is that you should get at least a 20 degree differential between inlet and outlet temps.

Check this before assuming anything else is failing (since you have an older Rv). Tape and seals in the ductwork just don't last 15 years.

A/C Ductwork collapse and rehab
2005 Newmar Essex 4502, 2013 Caddy SRX
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Old 06-26-2013, 07:49 PM   #4
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you might check to see if the filers and coils are clean since you indicate the air doesnt blow very fast. The thermostat is just a switch that turns the unit off and on at trmperature. While it can change the fan speed, it doesn't make the compressor cool any more or any less.
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Old 07-02-2013, 02:36 PM   #5
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We had the capillary tube/bulb/thermistor/sensor/thingamajig on our roof AC unit pushed really deep, up into the ventilation intake for the roof air. I have heard that this can give a false reading of cool air inside the airbox, while the interior of the coach never quite cools down enough....

Look for an uninsulated, thicker "copper" solid-core type wire on the intake side of the roof air unit. The wire should be pliable and bendable, but not bent at sharp angles. (You will have to remove the filter and/or the shroud to access) Make sure that this conductor is at the same level/close to the open foam air filter media of your intake to the Roof air. Make sure you do not put any sharp angles on the conductor as it could fatigue and break off. (Think of flexing a wire coat hanger over and over....*snap!* )

Give time for the system to adjust to the new thermal zone in the intake and I think you'll be pleased with the result. It's not going to get you down to deep freeze temps, but you should notice a difference.
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Old 07-02-2013, 02:44 PM   #6
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I'd start by cleaning coils on the roof and the filter behind the grid in the ceiling. Once the grid is off the ceiling, look for poorly sealed joint between ceiling and A/C.


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