AC freeze up

[Chris013]

AC is freezing up. I have cleaned the coils as previously suggested and thought it worked. However, this weekend it froze up again; any suggestions?

[TXiceman]

Have you checked the air flow?

Are you running the fan on low speed....if so, go to high speed.

Have you checked for air leaks between the inlet and outlet side of the unit?

The coil you cleaned...was it the inside coil (evaporator)?

Is the "freezestat" sensor located in the proper place on the evaporator?

A few thoughts. Have you seen any oily residue on any lines or fittings ...this could be a clue to a leak and you could be low on refrigerant.

Ken

[cb1000rider]

I would start with the freeze sensor.
We'd need to know make and model of your unit.
Dometic has a freeze sensor in the coil, I'm sure Coleman and others have the same. New ones are thermistor - meaning they change resistance with temperature and your AC control should kill the compressor and keep the fan going when it gets too cold.

Thermistors don't go bad very often, but they can be tested via a ice water and an ohm meter.

There may be a "switch type" freeze sensor too - someone else will have to chime in...

[Shadowcatche]

The ultimate cause may be low freon and an HVAC place should be able to recharge it (with less cost than an RV repair place). BUT try the other less expensive stuff first.
I find that some times having some one that knows what they are doing is worth the cost and lack of frustration.

[TXiceman]

Recharging an RV unit is not as simple as a home unit. The RV units are sealed and therefore no access ports.

First you have to install a saddle or piercing valve to gain access to the systema nd remove the remaining refrigerant. The system needs to be pressurized and checked for leaks first. Once the leaks are identified they need to be repaired. To solder on the copper lines, you need to purge thesustem with nitrogen to prevent contaminating the system. Now you need to solder in Schrader valves to finish the job. Now, evacuate the system to get the nitrogen out as well as any moisture. Now you are ready to recharge the system.

A refrig tech will probably charge you 3 to 4 hours for the work plus the parts and refrigerant. You can be up to a $500.00 bill pretty quickly.

At 1/2 the price of a new unit is when I would consider replacing the unit in total and getting a warranty on the NEW unit.

Ken

[Rockdad]

TXiceman described very well the 'proper' refrigerant leak repair. And thats exactly why I stopped doing RV AC repair work at our shop. The cost on refrigerant leak repair and recharge often cost as much as the AC unit was worth. Had to many people want a quicky recharge job without fixing the leak which often led to a 911 calls on the weekend because it went low on refrigerant again.

It can be be a few other things as well though. I see you checked for dirty coils. Ive found motors that were actually turning slow to even slowing down after a period of run time. If everything checks out your up to installing a service port and getting some gauges on it to check the refrigerant charge.

[WOMD]

Originally Posted by Shadowcatche

The ultimate cause may be low freon and an HVAC place should be able to recharge it (with less cost than an RV repair place). BUT try the other less expensive stuff first.
I find that some times having some one that knows what they are doing is worth the cost and lack of frustration.

Well I was going to suggest getting the unit re-charged but someone beat me to it.

Glad to see a knowledgeable community!

[Chris013]

Thanks everyone for your help. I will take it the RV shop this winter as it seems a little much for one with little time and knowledge.

[cb1000rider]

Just be aware that a new unit is in the $600 range. If re-filling with refrigerant, which will require soldering, the AC tech will need to find the source of the leak. I can easily see this becoming a $300 repair if you're not careful.... I basically consider these things "sealed" systems.

Diagnosing other causes of freeze issues - it's a little intimidating, but honestly, there isn't that much to it. Just post photos of the unit and we can get you started!

[Rockdad]

I was always forever nervous whenever I was on top of someones rig working an AC unit about damaging a roof. Would I be the one to step on weak spot the owner didn't know about or get a call later on telling me I caused their roof to leak.

[Chris013]

Originally Posted by TXiceman

Have you checked the air flow?

Are you running the fan on low speed....if so, go to high speed.

Have you checked for air leaks between the inlet and outlet side of the unit?

The coil you cleaned...was it the inside coil (evaporator)?

Is the "freezestat" sensor located in the proper place on the evaporator?

A few thoughts. Have you seen any oily residue on any lines or fittings ...this could be a clue to a leak and you could be low on refrigerant.

Ken

Finally back to the farm and can look at AC unit first hand.
We have been running at full speed
Checked for air leaks and do not see any.
Yes, it was the inside coil. However, looked at the exterior coil this I morning and it was clean.
If that is the copper wire it is just above the interior filter.
No oily residue any where that I have seen.

[ga traveler]

As cb1000rider said, There is a freeze detector. When we had freeze problems,Most of the time, the freeze detector had fallen out of position. Push it back into the coil or snap it back into position. (according to which type you have.)

[Chris013]

Originally Posted by ga traveler

As cb1000rider said, There is a freeze detector. When we had freeze problems,Most of the time, the freeze detector had fallen out of position. Push it back into the coil or snap it back into position. (according to which type you have.)

Is the freeze detector the copper wire hanging free just inside interior filter?

[mfire1339]

yes!