A/C starts & stops

Slap · 08-27-2020, 04:51 PM

Hello.
I have a 2019 White Hawk 32KBS and have a question on the ac.
When using the ac it cools nicely as it should, but as it reaches the desired temp the compressor starts and stops with no delayin the cycle.
Is the problem in the thermostat or the ac?

CAG · 08-27-2020, 05:18 PM

I am not sure I am following what you are explaining. Are you saying the fan continues to run but the compressor cuts off once it reaches the set temp? If so that is what it is supposed to do. With mine if it is set on hi or low cool it does that. If set on one of the auto cool settings (hi or low) it shuts everything off when it reaches the set temp. When it warms up, everything comes back on.

Slap · 08-27-2020, 05:52 PM

The fan does not stop and there is no delay between the compressor starting and stopping. There is no 1 or 2 degrees between cycles.

CAG · 08-27-2020, 05:56 PM

So then what are you saying? I'm confused. What is it doing?

Slap · 08-27-2020, 06:01 PM

What is happening is the fan continues to run constantly while the compressor cycles on and off without a pause between cycles.

CAG · 08-27-2020, 06:21 PM

That is normal. At least in mine. If your thermostat is set on Hi or Lo Cool the fan will continue to run and the compressor will cycle as needed. If your thermostat has an AUTO setting, set it on hi or low AUTO. It will shut off between compressor cycles.

Cavie · 08-27-2020, 06:21 PM

Quote:

Originally Posted by Slap

The fan does not stop and there is no delay between the compressor starting and stopping. There is no 1 or 2 degrees between cycles.

If you are seeing 1 or 2 degrees between cycles then you must have a good digital t-stat. Put the fan on "Auto" and it will stop and start with the compressor. You get a few min of quiet time. You should only need low fan speed at night. Close the ceiling dump on the main unit and let it all go into the duct work if you have a ducted unit.

JaycoMLOK · 08-28-2020, 05:01 AM

I think what the OP is saying that when the compressor shuts off it’s only seconds and it back on. If so it shouldn’t be doing that at least I’ve never had any that supposed to work that way.

CAG · 08-28-2020, 11:37 AM

Quote:

Originally Posted by JaycoMLOK

I think what the OP is saying that when the compressor shuts off it’s only seconds and it back on. If so it shouldn’t be doing that at least I’ve never had any that supposed to work that way.

Unless you live in a very hot climate like Arizona. Granted a few seconds might be a little fast but it does not take these badly insulated RVs long to heat up.

RogerR · 08-28-2020, 11:49 AM

Any chance the thermostat is in a hot location with a direct flow of air blowing right on it?

Test this thought by putting a cardboard box with one side open over the thermostat. Move the side with the hole away from air flow and see if it stops this problem. Some thermostats have an adjustment as to amount of temp drop before it triggers and you might also consider looking at that.

Or the thermostat is toast. If all else fails and you have your old one reinstall it and see what happens.

2edgesword · 08-28-2020, 12:09 PM

On my unit the fan is so loud I can't hear when the compressor is or isn't running. My question would be are you sure it's the compressor starting and stopping rather than just the fan?

Slap · 08-28-2020, 01:09 PM

Yes the fan is very loud, in fact too loud.
When I used it it was in the 90s. This is a new trailer so the thermostat may not be the problem. The thermostat is on an inside wall, I will check if it gets overheated and
i will check if there is an adjustment for cycling.
Thanks all it gives me something to check.

CAG · 08-28-2020, 01:55 PM

They are all loud. Nature of the beast, unfortunately.

Screwby · 08-28-2020, 03:11 PM

You could be having an issue called “short cycling” mine used to do that until I read up on the issue. To solve it just leave the fan in the “on” position not the “auto” position. Something to do with the fan keeping constant air moving across the coils/radiator in the AC to keep the temp constant, also prevents icing up in humid weather.

Mine would be cooling and then shut off, and immediately turn back on. Once I set the fan to “on” it never did it again

JimD · 08-28-2020, 05:14 PM

I believe there should be a built-in delay to prevent the compressor from immediately coming back on. This may be able to be verified by turning off the thermostat and as soon as it has stopped, turn it back on. I don't think it should be able to immediately come back on.

I read online that there may be a delay in the ac itself and in the thermostat (if it is not the mercury switch cheapie). Sometimes the one in the thermostat can be disabled or adjusted.

I have always thought, probably from researching, that the compressor delay is there to let the high condenser pressure dissipate allowing it to start easier the next time and save some component stress.

**JFlightRisk** · 08-28-2020, 05:28 PM

snip...

Quote:

Originally Posted by JimD

I have always thought, probably from researching, that the compressor delay is there to let the high condenser pressure dissipate allowing it to start easier the next time and save some component stress.

That's exactly why there's a 136 second delay on our EMS. If there's an outage that comes back right away, it'll delay power to the TT for that length of time to keep the A/C happy.

Screwby · 08-28-2020, 05:58 PM

Google “short cycle AC in RV”

It’s a very common occurrence

Fire&Ice · 09-09-2020, 05:54 PM

If you have an electronic style thermostat then you very well could have what is known as a "differential" setting you can program so that you can stop compressor short cycling. If you have the old mercury style, not so much. You can go into many of the electronic style thermostats and raise your differential setting up a couple degrees eg compressor shuts off at 75 degrees and comes back on at 78degrees. You might have your current t-stat with a one degree differential setting currently.

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