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Old 03-24-2015, 01:33 PM   #1
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Dometic Roof AC stops briefly then resumes

Hey gang,

So the front Dometic rooftop AC in our 351 GT will sometimes stop for about 3-5 seconds, then resume. It tends to do this mostly when we turn it on and it's cooling down the coach initially. Fan is set to "auto". This happens whether both AC's are on or just the front. It cools fine, but the occasional stop/start cycle seems odd.

Theories?

Thanks,

-Mike
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Old 03-24-2015, 01:37 PM   #2
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Mine does the same thing. Normal ops as it switches from high to low (or vice versa) fan ops I think. My previous RV's Dometic AC did the same thing too. Never caused or seemed to be a problem.


Setting the fan to Low or Hi stops this switching but the fan will run constantly that way too.
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Old 03-24-2015, 01:56 PM   #3
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Normal operation. May be due to freeze prevent or fan speed change (typically will switch to low fan speed when within about 4 degrees of set temp). That's the way mine functions.
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Old 03-24-2015, 10:02 PM   #4
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Quote:
Originally Posted by 43D18 View Post
Hey gang,

So the front Dometic rooftop AC in our 351 GT will sometimes stop for about 3-5 seconds, then resume. It tends to do this mostly when we turn it on and it's cooling down the coach initially. Fan is set to "auto". This happens whether both AC's are on or just the front. It cools fine, but the occasional stop/start cycle seems odd.

Theories?

Thanks,

-Mike
Normal operation, when in auto the compressor starts, with the fan in high. As temp approaches set point, unit stops then shifts to low speed fan. With set point reached, unit will cycle off.
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Old 03-25-2015, 01:57 PM   #5
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Air cond

The fan will change speeds automatic when it does the unit will hum for a second or two then come on at a different speed that's normal
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Old 03-26-2015, 08:00 AM   #6
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Hi guys! 43D18
Today my THIRD AC unit will be installed. Both previous units did the same thing as yours sooo it's possibly the speed change but the delay is too short from shut down to start up. The compressor doesn't stop my guess is the thermostat is the problem. These are single zone units. Th RV repair service I use was told that RF signles could cause the problem. I doubt that very much. If that was the problem it would happen whenever the Microwave started, your router or indoor/out door thermometer signaled the indoor unit etc. It appeares to me that Dometic has very serious issues with these units. One of mine was out of refrigerant the second unit freezes up (low refrigerant) even though I installed a new freeze sensor. There is something with the electronic controls and possibly the thickness of the tubing used in the evaporator and condenser. Good luck!
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Old 03-28-2015, 08:37 PM   #7
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Normal operation, when in auto the compressor starts, with the fan in high. As temp approaches set point, unit stops then shifts to low speed fan. With set point reached, unit will cycle off.
Thx for the replies, gang. That's exactly what it happening and makes perfect sense.

-Mike
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Old 03-29-2015, 06:31 AM   #8
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Hi 43D18
Just a note about my AC. The new one was installed (under warranty) and for the first time this unit works properly as in VinceU's post. This time the unit was replaced along with the controller and thermostat
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Old 07-15-2015, 06:39 PM   #9
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We have had the same issue with cycling on and off. Still not fixed 2015 Columbus 375RL.
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Old 07-15-2015, 07:12 PM   #10
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Sometimes the ac will pause for a second or two and will switch fan speed this is normal don't know if that's what you are hearing but just a reminder that the ac will do that


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Old 07-15-2015, 08:22 PM   #11
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I always run mine on Low and never really use the Auto mode (well, very rarely). Mine does this even on Low, especially when we first turn the unit on. I am concerned but it seems to always do this. I've been monitoring and think I might have to at least question it. I'm with oldProf....so wondering if there really is a problem.
My previous unit (travel trailer with a 15K BTU unit) never did this. Turn it on and it just ran....
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Old 07-15-2015, 10:28 PM   #12
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From my understanding this is normal when the unit is in the auto mode. I know on some TT and FW there is no auto mode and only works in low/high fan speed that is why they did not cycle. On my MH both my units do the cycle mode and have not had any issues.
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Old 07-16-2015, 08:52 AM   #13
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Update- the unit continues to do this but operates fine and it seems clear that this is a normal phenom.
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