Question about Dometic Rooftop RV Air Conditioner

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Ac fan will not run on auto only on on. the thermostat has been replaced

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  • camper2001 Sep 28, 2010

    the ac works great in the on position. The compressor still runs but the fan stops in the auto position.

  • camper2001 Sep 29, 2010

    duo therm camper roof air works only in the on position. When switched to auto position the ac still runs but the blower stops.The thermostadt has been replaced. thanks

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Hi,
From what you are saying there must be two separate relays that run the fan. The switch or thermostat must run two separate wire from it to something. one wire would be the "on" and the other the "auto". These would have to go to separate relays and the relay for the "auto" is bad...the realys may be on a circuit board and the whole board may need to be replaced.
Best thing to do is to follow the power for each position and find out where the power is stopsing in the auto position and why it is not turning on the fan. It may take a bit of detective work to actually trace down the problem. It could be as easy as a loose connection...

heatman101

Posted on Sep 29, 2010

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If the A/C compressor relay is not starting the compressor then the fan will not run. The compressor should kick on, then the fan will start blowing. But it sounds like you have a problem with the compressor, starting relay, or the starting capacitor. You can check voltage on the compressor side of the relay to see if you are getting power to the compressor. If you are getting power to the compressor then check continuity on the capacitor. Be sure to unplug the unit before testing capacitor. If you have continuity on the capacitor then the capacitor is good. I don't believe this system has a low pressure switch. So this would mean that your compressor is bad.

Posted on Sep 28, 2010

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Posted on Jan 02, 2017

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2 Answers

2002 4 ton Bryant air conditioner shuts off, fan still runs but not cooling is problem in the controls in the attic or in the AC unit or both?


With a non heat pump it is a simple 24 volt AC control circuit. In the attic there is a relay that is actuated via the fan control wire directly from the thermostat. On the thermostat there is an auto/man switch that controls the fan. Manual the fan runs all the time. Auto fan turns on and off with the outside compressor.

If the system is not calling for cool and the fan continues to run the fan relay is sticking. common problem. Sometimes after running for several days the relay will stop sticking if not, replace relay.

If the system is calling for cool and the compressor stops I would still expect the fan to run until thermostat tells the A/C to off. Some compressor units include a safety switch or high-pressure cut-out switch A blocked internal valve bad control board or external fan in outside unit defective no air flow in outside unit.
High pressure cut out not good,

Suggest turning temp max cool and observe. If acceptable cool and the compressor runs without interruption all is good, except for the blower in the attic. Safely check relay in attic blower circuit.

Hope this helps.

thermostat-heat-cool-fan-on-czwsw2ci0layswcsyy3dj4dr-4-2.jpg

basic-thermostat-wiring-diagram-czwsw2ci0layswcsyy3dj4dr-4-5.jpg

Jun 28, 2017 | Bryant Heating & Cooling

3 Answers

Fan doesn't work in heat mode it works on all other functions. Heat does come out but fan doesn't kick in. Outside unit is operating


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Nov 01, 2015 | Heating & Cooling

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No fan when ac kicks on Ihave a eb15b funace with a coleman ac


The heat will normally use a low speed on the fan, & the AC along with the fan switch on the thermostat will use the high speed. The thermostat turns that high speed on when there is a call for cooling & is the same switch if you were to manually turn the fan from auto to on. Try turning the fan on @ the thermostat. If it works, then replace your thermostat. If it doesn't, it could be a bad fan speed, a bad fan relay on a control board or external relay, or a loose or broken green thermostat wire.

Apr 14, 2014 | Coleman Home Electric Furnace Eb15b/Eb15d

1 Answer

I have an old RUUD central AC unit that started blowing hot air. I set the thermostat to off and set the temp gage higher than air temp to turn the unit off and save money, but inside blower unit runs...


Hello

Okay did you check your thermostat to see if you have the fan switch on auto? The switch must be on auto or the fan will continue to run. If the thermostat fan switch is on auto then there is a malfunction in the thermostat probably. You can go to your forced air unit and on unplug the unit. That way it will not turn on at all, because the forced air unit is controlled by the thermostat. Hope this helps.

Jul 26, 2009 | Heating & Cooling

2 Answers

Unit will run if the thermostat is switch on ON, but if left on AUTO unit will hum and won't run.


For most Thermostats on and auto is for the fan switch function. There s usually another button for heat off cool. When you turn a\c or heat on , the fan switch should be on auto.

Jul 10, 2009 | Heating & Cooling

2 Answers

Fan will come on for heat(auto), but not for AC or set to ON


You have a blower relay in the furnace that's probably bad. In the heat mode the blower is on a temperature relay, in cooling mode the blower has to come on immediately so there is another relay for cooling. The green wire on the thermostat feeds that relay, so if you go to the furnace and shut the power off and find the green wire from the thermostat that feeds that relay and replace it, being careful to mark all the wires before removing them, also the relay terminals have numbers for identification.

Apr 07, 2009 | Heating & Cooling

1 Answer

WHEN TERMOSTAT IS IN AUTO POSITION THE HEAT OR AC WILL START BUT THE FAN WII NOT RUN. THE FAN WILL RUN IN THE ON POSITION.


you either have a wrong connection or a defective thermostat.

the fan when switch to auto will run as the heater or ac is running and when in the "on " position, it will always run.

there is a problem in the connection of the cool or heat contact to the fan relay that is why it is not running if you place it on auto.

trace the diagram of the thermostat and you would know where the problem is...

i hope i ws able to solve ur problem..

pls rate me

tnx 4 using fixya..

drcool




Jul 23, 2008 | Heating & Cooling

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