Duo Therm Front A/C not working correctly

[BigLar368]

Well since day one our front A/C (zone 1) has not worked properly (2004 Monaco Camelot). Sometimes it take a while for it to start but usually works well on hot days. Getting ready for a trip and have it hooked to shore power testing everything and the front does not want to start. Fan functions correctly in manual mode but the compressor does not even try to start. Do some investigating and find there is a temp sensor wire hooked up to the control board. Wife located the sensor near the front TV. There is no cover on it. Wife pulled it our some and now it seems to be working. I have not ohm'ed out the sensor yet as I am at work. Could this sensor work intermittently? Can the control board work intermittently as well? I went ahead and ordered a control box even if it is just used for a spare down the road. If it happens again I will try and unplug the sensor and default the temp sense to the thermostat. Thanks in advance.

[wa8yxm]

Re the sensor
Two possible issues: Bad sensor. Loose wire "pulled it some and now it works" strongly suggests loose wire.

page 2: Many RVers have a few screws loose... Specifically the screws that hold the wires in the Power Distribution panel, Power inlet (And shore cord outlet) and if the wires connect to that sensor with screws.... Them.

(I hope you did not think I was speaking of a different kind of screw)

[BigLar368]

Thanks for the help. As of now it's working just fine. I will keep the temp sensor and the control box in the RV as a spare. Thanks again for the help.

[dougrainer]

BigLar368 wrote:
So you are saying just plug in the new temp sensor and leave it in the air return so to use the return air for the sensor to work off of? Thanks for the help thus far.

Yes. Some OEM's did that. Doug

[BigLar368]

So you are saying just plug in the new temp sensor and leave it in the air return so to use the return air for the sensor to work off of? Thanks for the help thus far.

[dougrainer]

BigLar368 wrote:
Doug, Thanks for dropping in. This front unit has me baffled. As of the last 2 days the unit is working properly. Dometic customer service told me that there would not be a remote temp sensor for the front unit and were not much help. My wife found the front temp sensor and tugged it out of the hole. Every since then it has worked properly. I have noticed it takes a couple of minutes to start as compared to my zone 2 unit (bedroom) which starts as soon as the thermostat is selected. I have read some posts that suggest the temp sensor should be routed to a more even temp area. As of now it's about 8 inches away from the windshield behind the front TV. I have since purchased a control box and remote temp sensor. I will keep them as a backup for future use.

1. Dometic and RVP Tech lines are NOT for retail people like you. Both will not talk you thru with defects. They will explain HOW the system operates. Most RV's the Wall tstat is the Zone 1 sensor. But, on some RV's they run a remote Thermister for Zones 1/2/3/4. Monaco made a mistake by installing the front Zone 1 sensors in the drivers side wood valance and up front by the TV cabinet. BOTH areas will not allow correct inside temp sensing. But, that is a Install by Monaco fault and not a Dometic fault. What I would do, is connect the NEW remote sensor to the Zone 1 control board and use the area above the intake filter as the sensor area.
2. That bulb at the end of the Temp Thermister. IF it is pinched or has any type pressure on it or the white wire loom holder is pinching it, that will cause incorrect operation of the AC unit, usually short cycling
3. The TIME of waiting when selecting various modes in each zone can vary. If you select AUTO/COOL, the fan will come on within 30 seconds and the compressor from 5 seconds to 2 minutes 45 seconds. If you select HI FAN/Cool, the fan will usually come on within 15 seconds and you will still have that 5 second to 2 minutes 45 seconds wait for the compressor(same with Lo or Med Fan speed). Doug

[BigLar368]

Doug, Thanks for dropping in. This front unit has me baffled. As of the last 2 days the unit is working properly. Dometic customer service told me that there would not be a remote temp sensor for the front unit and were not much help. My wife found the front temp sensor and tugged it out of the hole. Every since then it has worked properly. I have noticed it takes a couple of minutes to start as compared to my zone 2 unit (bedroom) which starts as soon as the thermostat is selected. I have read some posts that suggest the temp sensor should be routed to a more even temp area. As of now it's about 8 inches away from the windshield behind the front TV. I have since purchased a control box and remote temp sensor. I will keep them as a backup for future use.

[dougrainer]

sdianel wrote:
1. Try a thermostat reset. Instructions should be in the manual for the thermostat or you can find them online. I have the instructions for the Comfort 5 button model if you need them, send me a private message.
2. We have 2 AC's in our '04 Country Coach. Both AC's must be on same fan mode "Low, Med or High" (one can't be on low and the other high). Have no idea why.
3. We recently had problems with our front AC not cooling and talked to a tech. He said in hot humid weather to run the fan on high. That keeps the unit from freezing and shutting down.
4. There is a phone cord connection inside the units. Unplug and plug back in.

1. A reset will NOT fix operational problems.
2. You can set EACH AC individually.
3. The units CANNOT freeze up. They have a Freeze Thermister that prevents freezing regardless of ambient conditions. Doug

[sdianel_-acct_c]

1. Try a thermostat reset. Instructions should be in the manual for the thermostat or you can find them online. I have the instructions for the Comfort 5 button model if you need them, send me a private message.
2. We have 2 AC's in our '04 Country Coach. Both AC's must be on same fan mode "Low, Med or High" (one can't be on low and the other high). Have no idea why.
3. We recently had problems with our front AC not cooling and talked to a tech. He said in hot humid weather to run the fan on high. That keeps the unit from freezing and shutting down.
4. There is a phone cord connection inside the units. Unplug and plug back in.

[BigLar368]

It's not trying to start. The problem is intermittent. In my experience when a start or run capacitor fails it's for good and will not work intermittently.

[MountainAir05]

did you also check the compressor start Cap, There are two, one for motor and one for compressor.

Easy to check, swap the cap for the compressor from the back and if works then the front one is bad.