RV A/C compressor not kicking on

K

KRS

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My dad's Wildcat trailer has a Dometic Dual Therm Quick Cool High Efficiency A/C unit on the roof.

The compressor quit working and I'm wondering if it's low on cooling gas (R134...?).

Is this like my truck, can I get a can, find the fitting, turn on the A/C and add R134?

I'm comfortable doing this on my vehicles, but this trailer setup is new to me.

Thanks for the help,

KRS
 
K

KRS

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Re: RV A/C compressor not kicking on

I don't see any gas fill-up fittings :(
 
SS MAYFLOAT

SS MAYFLOAT

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Re: RV A/C compressor not kicking on

I looked at the spec tag on the compressor. Under the 115 Volt is R22. This is the refrigerant that it uses. That unit sure looks as if it was underwater at one time. I've seen that flood mud many times :D....(Aug 2007,,,my shop)

If it was under water, the stat and safety switches could have an open circuit not letting the compressor get its power. Small units like that does not have a low pressure cut out like a car does. The only protection that unit has is a thermal overload which is located under the plastic cover on the compressor. Absolutly do not mix R134a with R22. The oils will not be compatable.
 
K

KRS

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Re: RV A/C compressor not kicking on

Thank you for the reply.

It's very dusty, live in the desert SW.

Hasn't been underwater, I won't ask about yours..... :)

KRS
 
SS MAYFLOAT

SS MAYFLOAT

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Re: RV A/C compressor not kicking on

If you had a leak, the oil would attrack a lot of that desert dust and would look wet. If everything is dry like it looks, your charge should be okay. Does the condenser fan kick on when you turn the unit on? If it comes on, then your compressor should come on as well. If the condenser fan does not come on, then you have an open in the circuit not allowing power to get to the compressor and fan.
 
K

KRS

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Re: RV A/C compressor not kicking on

Didn't know about condensor fan, let me check tonight,

KRS
 
hrdwrkingacguy

hrdwrkingacguy

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Re: RV A/C compressor not kicking on

does that unit have a dual shaft motor thats a blower motor on one side and a condenser fan on the other? The schematic shows only one motor...If the motor runs and its a combo condenser fan and blower motor but the compressor doesn't then the next step is to check for power across the overload when you turn on the unit...If you put a meter on each terminal of the overload(there should be two, a blue and something else) and you have power then the overload is open..If its not then its time to look at the PTC and start cap...Testing the PTC isn't something I can explain now, but the cap has a microfarad rating at a voltage like 25uf @ 220v...You need a meter with a |( or microfarad setting to test it...I don't see low pressure or high pressure switches in the pictures or in the schematic...The compressor should run if their is power and the starting accessories are good...

So power to the compressor and no start means...

open overload
bad starting accessories
bad compressor windings

To check for bad windings take off the wires to the C S and R terminals at the compressor...The readings should add up when you ohm them...Something like C -> S = 14ohm C -> R = 6ohm S -> R = 20ohm...That's just and example but if the something read 0ohms you have an open winding and a bad compressor...:eek:

PS never "jump" anything...That's a recipe for a bigger bill, weather it be repair or hospital...This unit has nothing but a 2TK overload for a saftey...So if the compressor dome is hot and the overload is open it needs to cool...if the compressor is cool and the overload is open it needs to be replaced...My initial thoughts are the run cap and PTC are bad due to heat...They are cheap and easier to replace if the compressor and the overload is good...
 
hrdwrkingacguy

hrdwrkingacguy

Petty Officer 1st Class
Joined
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Messages
368
Re: RV A/C compressor not kicking on

you have a run cap(The silver thing with two terminals) a start cap and a PTC thermistor...Any of these things can be bad and cause a problem...The PTC is the black, round thing with wires on either end...

Link to test a PTC...

So the things we no so far...

You do have power to the machine
The relay/contactor that starts the compressor is good
the overload is closed

things we don't know...

Are the compressor windings good
is the start cap good
is the run cap good
is the PTC good
is the compressor locked up

ohms test on a capacitor doesn't tell you anything...Basically it had a little charge and when you connected your meter is dissipated the voltage and then had no resistance from one side to the other...That basically tells you that it is in fact a capacitor...You need a cap tester to tell you if its good or not...Or you can go the a parts store and buy a new one for 5$...The start cap is the same thing...The PTC is a thermistor that opens as it gets hotter and removes the start cap from the circuit...My guess is one or more of these devices are bad...:eek:
 
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