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Topic: AC on and off (Read 645 times) previous topic - next topic

AC on and off

My bedroom AC will cool anywhere from 15 to 45 seconds and then shuts off for a minute or so before it kicks back in.  This cycling keeps repeating it self no matter what temp I set the thermostat at.  If I set the fan on either high or low it continues to run even when the AC cycles on and off so I'm eliminating a communication problem between the thermostat and unit.

I'm thinking the compressor is locking up and it's time to replace the original Duo-Therm.  Would very much appreciate any thoughts...

Gary
Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"

Re: AC on and off

Reply #1 –
Gary,
Is the air flow restricted? Dirty filters and cooling coil fins?
John Duld
1995 U320C SE 40'

Re: AC on and off

Reply #2 –
John...filter and coils are very clean, when the unit runs I ihave cold air and good air flow.

Gary
Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"

Re: AC on and off

Reply #3 –
Gary,

Do you have  heat pump A/C units?
Or do  you have a standard A/C units with strip heat?

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: AC on and off

Reply #4 –
Gary,

It probably the compressor "run capacitor" is out of tolerance and needs replacement.

Jim
Jim Frerichs
2002 U320 42'

Re: AC on and off

Reply #5 –
Pamela & Mike the unit has a heat pump

Jim...I was reading in the manuel there is a way to test the run capacitor with a volt meter which I will attempt to do since I do not have a capacitor tester.  Would using a meter be a fairly accurate way to determine if it is out of tolerance?  I hate to just throw parts at it but it would be worth it if I'm not able to test it.

Thank you, Gary
Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"

Re: AC on and off

Reply #6 –
Gary,

You also need to check the coil that activates the cool or heat.  It should be energized when the unit is in the cool mode.  If the coil is overheating it can cause the unit to oscillate on and off. Most of the time the coil just dies but have seen them overheat also causing symptoms you describe.

If you are getting cold air as you described in reply #2  then your compressor isn't locked up as you mentioned in OP.

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: AC on and off

Reply #7 –
Gary,

I think the only way be accurate is to use meter that has as capacitance scale(s) to see if the values are above or below the number printed on the capacitor. Too high or too low is not acceptable. Using capacitors with the wrong (high or low) due to degradation will make the motor run hot and thus eventually hit the thermal limit cut-off and causing the compressor to stop...which may be what you are having happen. However, your symptoms of short-cycling also could be caused by something else entirely, as other have suggested.

The capacitance value for the start capacitor is quite a bit bigger than the capacitance for the run capacitor. It takes more to boost the motor to start as compared to keep it running efficiently.

Often you will find both run capacitors and start in the same package - three terminals instead of two. Follow the wires from the compressor (or fan motor as well) to find them. Photo what you see and maybe label the wire connections too before you touch and remove the wires. AND be sure to discharge/short together all the connections on the capacitor with a screwdriver tip before touching them- there can be a very nasty shock if you don't do this before touching them.

Usually you can find a replacement capacitors from most air conditioning service vendors, electronics supply warehouses or on-line from providers such as Digi-Key or Mouser. It is best best to buy capacitors with values that are the same as what is printed on the old capacitor.

Jim

2002 U320
Jim Frerichs
2002 U320 42'

Re: AC on and off

Reply #8 –
Most of these small units will have a capacitor for the fan a compressor run capacitor and a separate start capacitor . there also will be a potential realay tht is attached to the start capacitor.  the relay is supposed to take the start winding out of the circuit once it starts to run.If it goes bad it will keep the start winding engaged and the compressor internal overload will trip as the compressor cools it will try and start a gain. It will continue this on and off cycle.
You can purchase a replacement at about any place thst sells sppliance parts or Grainger carries them as well as the capacitors.
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: AC on and off

Reply #9 –
In the fall of 2014 I replaced the coil when the unit would cycle between cool and heat.  When trouble shooting that problem I found the coil would get hot while cooling and that's when heat would automatically kick in.  Once the coil cooled the unit would start cooling again.  So after Pamela & Mike's post I'll be checking the coil for heat before replacing the run and start capacitors.

However, before I do anything I'm going to bring the coach home tomorrow and check and see if it acts the same when I turn the heat on.  Not sure if that will help in narrowing down the cause of the problem but I'm so far in over my head when it comes to trouble shooting AC problems it will be worth a try.

I really appreciate all the feed back in helping me solve this problem.  When I find the cause of this problem I'll report back.

Gary
Gary Mauck
Deerfield Beach, Fl.
2005 U320 40' PBGB

"Elks Care, Elks Share!"
 

Re: AC on and off

Reply #10 –
Quote from: Gary & Jeannie –
In the fall of 2014 I replaced the coil when the unit would cycle between cool and heat.  When trouble shooting that problem I found the coil would get hot while cooling and that's when heat would automatically kick in.  Once the coil cooled the unit would start cooling again.  So after Pamela & Mike's post I'll be checking the coil for heat before replacing the run and start capacitors.

However, before I do anything I'm going to bring the coach home tomorrow and check and see if it acts the same when I turn the heat on.  Not sure if that will help in narrowing down the cause of the problem but I'm so far in over my head when it comes to trouble shooting AC problems it will be worth a try.


I really appreciate all the feed back in helping me solve this problem.  When I find the cause of this problem I'll report back.

Gary
The compressor works the same in heat or cool mode. The freon flow just reverses from heat to cool when the coil is activated. If the unit runs well in heat mode, and cycles on and off on the thermostat setting, you can be pretty sure the start and run capacitors are okay. You can check the reversing valve [coil]  by pulling the coil off the reversing solenoid valve and putting a screwdriver in the coil. With a call for cooling from the thermostat the coil will attract the screwdriver, [coil will normally be actuated and allow cooling], if it does not, coil or wiring is bad.
You can also feel the reversing valve when the coil is on it. There will be a noticeable click when the valve opens for cooling mode, nothing happens when in heat mode because no power is sent to coil.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.