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Old 07-21-2021, 08:40 AM   #1
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AC cycles too fast

Our Dometic AC cycles too fast. It will run, kick off, and less than 5 seconds later kick back on. It's 15000btu on a 2018 297RKS. This year we added a second AC thinking it was just working too hard, but it is still doing it. Any ideas as to why? Is it something to worry about or just put up with? Thx guys and gals. I love this forum.
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Old 07-21-2021, 09:05 AM   #2
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Check to insure that cool air is not blowing directly on Thermostat.
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Old 07-21-2021, 12:09 PM   #3
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Is it even possible for it to come back on just seconds later? I thought pressure had to come back down for compressor to re-start.
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Old 07-21-2021, 12:18 PM   #4
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Is it even possible for it to come back on just seconds later? I thought pressure had to come back down for compressor to re-start.
The delay timer usually only controls the compressor and not the fan.
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Old 07-21-2021, 12:22 PM   #5
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Yes, I thought he was referring to compressor since he said it 'cycles' too fast.
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Old 07-21-2021, 08:10 PM   #6
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I dont honestly think it's just the fan. The ac stops then kicks right back on. Its cold air. There is nothing blowing on the thermostat.
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Old 07-21-2021, 08:34 PM   #7
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Are you in the shade when this happens are wide open sun. What temp do you have the thermostat set on. Except for the very upper end, high priced units, these things heat up like a carboard box in the desert. Could be the setting on the thermostat and sunlight making your AC work harder. Very hard to get these rigs to stay constant in temp. Slideouts are not energy friendly either.
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Old 07-21-2021, 09:03 PM   #8
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I dont honestly think it's just the fan. The ac stops then kicks right back on. Its cold air. There is nothing blowing on the thermostat.
We were parked next to a GeoPro this winter in FL. Theirs did the same and it was annoying as hell. When we asked them if this behavior was normal, they said yes and that the unit had an inverter compressor. It had done this since new and their dealer said it was how the new inverter compressor units operate, the compressor ramps up and down. They said it was even more annoying inside and would turn it off at night because they couldn't sleep with the constant cycling.

I hadn't realized this technology was available in R/V units but according to them it is. I've since looked them up and Dometic makes them. Much lower start up amps too. Should be good for generator use though.
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Old 07-21-2021, 09:08 PM   #9
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Originally Posted by S.kimbruce View Post
Our Dometic AC cycles too fast. It will run, kick off, and less than 5 seconds later kick back on. It's 15000btu on a 2018 297RKS. This year we added a second AC thinking it was just working too hard, but it is still doing it. Any ideas as to why? Is it something to worry about or just put up with? Thx guys and gals. I love this forum.
Does your other ac do the same thing? That doesn't sound normal, Are you perhaps operating another appliance, like the microwave, that might cause and interruption of power?
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Old 07-22-2021, 07:02 AM   #10
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We were parked next to a GeoPro this winter in FL. Theirs did the same and it was annoying as hell. When we asked them if this behavior was normal, they said yes and that the unit had an inverter compressor. It had done this since new and their dealer said it was how the new inverter compressor units operate, the compressor ramps up and down. They said it was even more annoying inside and would turn it off at night because they couldn't sleep with the constant cycling.

I hadn't realized this technology was available in R/V units but according to them it is. I've since looked them up and Dometic makes them. Much lower start up amps too. Should be good for generator use though.
I just looked up that Dometic inverter AC unit too. Interesting. Must be on brand new units, previously Coleman Mach units were used. Couldn't read much on them though, Dometic site was trying to force me to accept cookies.
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Old 07-22-2021, 08:08 AM   #11
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Does your other ac do the same thing? That doesn't sound normal, Are you perhaps operating another appliance, like the microwave, that might cause and interruption of power?
The other unit does not do it. Nothing else is on. We are qite often outside when it does it.
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Old 07-22-2021, 08:16 AM   #12
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Are you in the shade when this happens are wide open sun. What temp do you have the thermostat set on. Except for the very upper end, high priced units, these things heat up like a carboard box in the desert. Could be the setting on the thermostat and sunlight making your AC work harder. Very hard to get these rigs to stay constant in temp. Slideouts are not energy friendly either.
It happens under both conditions. We usually park by trees so shade most of the time. The thermostat will vary from 72-78. It isnt even when it is the hottest out. Our thermostat is reasonably protected so as to not be influenced by air blowing or sun baking.
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Old 07-22-2021, 08:19 AM   #13
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This could be a faulty thermostat that doesn't allow enough cycle delay between the time the temperature reaches the set temperature and when it wants more cold (or heat depending) on the setting.

Look for one that allows setting of the cycle rate. This will probably require reading a lot of fine print.

Too tight a cycle rate like 1 can cause very frequent cycling simply 'cuz the temperature swings 1 constantly.

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Old 07-22-2021, 08:45 AM   #14
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This could be a faulty thermostat that doesn't allow enough cycle delay between the time the temperature reaches the set temperature and when it wants more cold (or heat depending) on the setting.

Look for one that allows setting of the cycle rate. This will probably require reading a lot of fine print.

Too tight a cycle rate like 1 can cause very frequent cycling simply 'cuz the temperature swings 1 constantly.

-- Chuck
That makes sense. We will have to check it out.
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Old 07-22-2021, 08:49 AM   #15
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Ok. Hubby took thermostat cover off and blew a lot of dust out. ��*will see if getting all of that out of the way will help. Has so far. Of course, I dont dust, but he does. Too easy��
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Old 07-22-2021, 08:52 AM   #16
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That's called the hysteresis setting in a thermostat, btw, if you have a thermostat which allows for adjustment of it.
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Old 07-22-2021, 09:08 AM   #17
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The Dometic A/C's also will revert to the low fan mode automatically when the temp is within approximately 4 of set temp. This is with fan mode set to auto.
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Old 07-22-2021, 09:29 AM   #18
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The Dometic A/C's also will revert to the low fan mode automatically when the temp is within approximately 4 of set temp. This is with fan mode set to auto.

To expand on this, when the A/C decides it needs to change the fan speed from high to low, or low to high, it momentarily shuts the fan off completely. This may be all that is happening. And it is annoying.
When mine is doing this, I usually lower the set temp by a couple of degrees and it solves the problem. (For a while)
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Old 07-22-2021, 09:54 AM   #19
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I don't know about the dometic but I have a furion that cycles too often in my opinion but not as bad as the OP.

In the furion the temperature sensor is in AC unit, not in the thermostat. I believe this is the main issue. If I want it to run steady I set the thermostat 10-15 degrees below what I want until the temperature inside gets close to what I want
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Old 07-22-2021, 10:34 AM   #20
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Mine does that. I've learned to live with it. Try taking your fan out of auto and see if it solves the problem.
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