A/C unit cycles excessively

[Denny and Angie Miller]

Hello all,
I am having excessive cycling issues with the main A/C unit. Runs a while, shuts off completely (no fan) then starts up again after just a minute or 2, does this constantly. 2017 HC 353RL. Acts as if there is no "dead band" between shutting down and starting up again. I thought it would be a simple thermostat fix, but after reading some other posts I'm wondering if the unit is freezing up. 95 here today with high humidity, water pours off the back. I read in another post about a service bulletin recommending running the fan constantly to prevent freezing...does any one have a copy of this bulletin?

[kdeiss]

Yes run on high fan do not close any of your vents to restrict air flow.
My guess is you are freezing up and freeze sensor is shuting the unit down but it should not be coming on that quickly

[Razrbk]

[QUOTE=Denny and Angie Miller;1067589]Hello all,
I am having excessive cycling issues with the main A/C unit. Runs a while, shuts off completely (no fan) then starts up again after just a minute or 2, does this constantly. 2017 HC 353RL. Acts as if there is no "dead band" between shutting down and starting up again. I thought it would be a simple thermostat fix, but after reading some other posts I'm wondering if the unit is freezing up. 95 here today with high humidity, water pours off the back. I read in another post about a service bulletin recommending running the fan constantly to prevent freezing...does any one have a copy of this bulletin?[/


How's your inside temperature?

[DQDick]

Once the rig starts to heat up in the morning I put both AC's on high fan and let them run all day.

[8amps]

Ours is doing that but coming back on within a second or two.

[kdeiss]

What I think you are hearing if you have fan in Auto when it shifts from high to low fan speed or low to high it will shut off for a few seconds then cycle back on! That is how my Dometic Brisk Air II works

[8amps]

Originally Posted by kdeiss

What I think you are hearing if you have fan in Auto when it shifts from high to low fan speed or low to high it will shut off for a few seconds then cycle back on! That is how my Dometic Brisk Air II works

So that is normal? It ran all day today, never shut off. It was warm today (80ish) but not broiling...

[kdeiss]

Yes that is Normal, On those real hot and humid days I recommend turning the fan from Auto
To high speed your fan will run constant.
When in auto fan ..if the set point is 5 degrees or more less then the room temp the fan will operate on high speed 4 degrees or less will run on low speed
Example stat set at 72 room temp 78 fan speed High ..... stat set 72 room 73 fan will run on low. Hope this helps

[Denny and Angie Miller]

Thanks kdeiss, I was unaware of the fan speed/temperature interlock while in auto.

[Denny and Angie Miller]

As an update, I found my return air ducts were both collapsed down to about 1" opening. I cut 1 1/4" pvc pipe into 6" sections and stuck those in there to hold the return duct open. I used aluminum tape to seal the duct/vent transition on the supply side. While doing that I used my phone as a video camera to inspect all the supply ducts, and didnt find any other issues. I did find 2 holes about 6" diameter each in the lower corners of the garage where cold air was pouring out, so I bought some black "great stuff" foam sealant and filled those. While I was there I went ahead and sealed the garage from the 2 propane compartments to prevent mud dobbers/wasps from getting in. I guess I'll surrender the propane compartments to them....Anyone use window screen to cover the large lower opening on the propane compartments?

[happy camper x2]

Dennys
after reading your post I went out and found a couple areas I fixed. Take down the divider in the basement there is a few areas you can plug to help keep cool. could you go more in detail about where you taped duct vent transition
thanks

[Denny and Angie Miller]

Originally Posted by happy camper x2

Dennys
after reading your post I went out and found a couple areas I fixed. Take down the divider in the basement there is a few areas you can plug to help keep cool. could you go more in detail about where you taped duct vent transition
thanks

I removed the vent covers for 3 reasons, to inspect the supply duct, to check if I needed to cut the vent flange down as other have done so it's not sticking up into the flow path of the air, and to remove every other slat on each supply vent cover. Here is a pic of a duct/vent transition that is partially taped with aluminum tape.

[unclesam]

I'm having the same problem with my 2016 Montana High Country 352RL, same rig as yours except I don't have residential fridge. My dealer eventually replaced my A/C under warranty and it's still less than spectacular. Will check return air ducts. Also I found an instruction manual online for our thermostat, see attachment.

[Denny and Angie Miller]

Originally Posted by unclesam

I'm having the same problem with my 2016 Montana High Country 352RL, same rig as yours except I don't have residential fridge. My dealer eventually replaced my A/C under warranty and it's still less than spectacular. Will check return air ducts. Also I found an instruction manual online for our thermostat, see attachment.

Thanks unclesam, the changes I have made seemed to have really helped. We have been camping in our rig all week and we have kept the thermostat at 71. Bedroom unit not aligned to the air ducts but fan on lo all the time. I switch the main unit from hi fan speed to auto at night

[unclesam]

Originally Posted by Denny and Angie Miller

Thanks unclesam, the changes I have made seemed to have really helped. We have been camping in our rig all week and we have kept the thermostat at 71. Bedroom unit not aligned to the air ducts but fan on lo all the time. I switch the main unit from hi fan speed to auto at night

I checked my return air and found some garbage; saw dust, wood chips and pieces of foam. I cleaned it out, measured duct (1 inch) and also installed a couple pvc pipes to increase space to 1 1/2 inches. I also removed the supply vent covers and just left them off. The unit seems to be working much better, no cycling on and off every 60-90 seconds. I forgot to mention before but during the on/off cycling, the A/C compressor didn't always kick on and then the unit would shut off for 10-15 seconds, then start up and go thru the same process again. I'm glad your unit is working better and mine seems to show much improvement also.

[Denny and Angie Miller]

Originally Posted by unclesam

I checked my return air and found some garbage; saw dust, wood chips and pieces of foam. I cleaned it out, measured duct (1 inch) and also installed a couple pvc pipes to increase space to 1 1/2 inches. I also removed the supply vent covers and just left them off. The unit seems to be working much better, no cycling on and off every 60-90 seconds. I forgot to mention before but during the on/off cycling, the A/C compressor didn't always kick on and then the unit would shut off for 10-15 seconds, then start up and go thru the same process again. I'm glad your unit is working better and mine seems to show much improvement also.

I have read in other posts that some theorize there could be some icing going on, and the unit senses this and goes into some sort of thawing cycle. I'm no a/c technician, but I do know that reduced air flow through the unit can create icing conditions, so providing an improvement in air flow through the unit has got to be helpful. Thanks again for the thermostat manual, I didn't have that before and it has some useful info.

[PeteandJoan]

Originally Posted by Denny and Angie Miller

I have read in other posts that some theorize there could be some icing going on, and the unit senses this and goes into some sort of thawing cycle. I'm no a/c technician, but I do know that reduced air flow through the unit can create icing conditions, so providing an improvement in air flow through the unit has got to be helpful. Thanks again for the thermostat manual, I didn't have that before and it has some useful info.

My living room AC did that off/on, shutdown, start back up routine until I cut down the vent lip and started running fan on high (or med some time but not low or auto). I actually heard what I figured was ice drop. Much better now....Thanks to the info I got on this forum about a year ago!

[Denny and Angie Miller]

Originally Posted by PeteandJoan

My living room AC did that off/on, shutdown, start back up routine until I cut down the vent lip and started running fan on high (or med some time but not low or auto). I actually heard what I figured was ice drop. Much better now....Thanks to the info I got on this forum about a year ago!

I have only been on this forum since May, but it has already helped me with several issues, and given me others to look out for in the future, especially before warranty runs out!

[8amps]

Originally Posted by happy camper x2

Dennys
after reading your post I went out and found a couple areas I fixed. Take down the divider in the basement there is a few areas you can plug to help keep cool. could you go more in detail about where you taped duct vent transition
thanks

What are you using to plug the openings? Expanding foam? Non-expanding foam? Steel Wool? Socks? Something else ?

[unclesam]

Originally Posted by 8amps

What are you using to plug the openings? Expanding foam? Non-expanding foam? Steel Wool? Socks? Something else ?

I used expanding foam in all holes under sinks etc. I also cut cardboard to plug all furnace vents in the floor and furnace return ducts under the steps. I did everything I could think of to prevent cold air from escaping, I'll remove cardboard in furnace vents and return air when A/C is no longer required.