a/c evaportor ice up

Terry W. · 06-06-2014, 04:05 PM

HELP OK here we go 2012 Avalanche 15k Coleman Mach main a/c evaportor is iceing up. Running on 50 amp service with solid 120 volts. Running on low setting as we are also using 13.5k in bedroom on low, 13.5 working well. Took shroud off unit rinsed outside coil off and cleaned pan. I have taped all seams between air delivery and return air. Filter is clean. I changed out the factory thermostat with a hunter digital and same thing happens. It puts out good cold air when not frozen up. I have the 3 vents open in the inside shroud. So now where do I go from here.

Bob Landry · 06-06-2014, 04:30 PM

Put a thermometer in the register and see what the discharge air temperature is. If it's down in the 40's which I suspect it's going to be, you have an air restriction somewhere or it's low on charge. It will feel like it's blowing super cold air, and it is, however, when you move away from the blower, you won't feel much because you aren't moving much air. Rule 1.. To cool air, you have to move air. It's not a common occurrence, but occasionally one slips by.

The unit can be checked for correct charge with a clamp-on meter that measures amps, but the tech has to be familiar with how to do it and it's beyond the scope of this thread.

If your AC is ducted, you should be able to open the vents on the bottom to direct all of the air through the bottom grill outputs, and it should not ice up running like this.

Terry W. · 06-06-2014, 04:45 PM

Thanks Bob. I put a digital meat therometer in inside the grill and getting about 58-60 degree air out. With the 3 vents in the grill open it still does it. Now all this is with the fan in "on" I just moved the fan to auto when I heard the compressor kick out to see what this does. My DW says I just want to be able to hang meat in here, but when it was 87 outside thermostat set at 70 it was saying 78 and 76 in here on 2 different therometers.

fla-gypsy · 06-06-2014, 06:27 PM

Have you tried it on High cool with the fan always on? It can make a difference in certain conditions by moving more air across the coils.

Terry W. · 06-06-2014, 06:33 PM

OK with the grill vents closed, air going into duct work it started to ice again. I now have fan in auto and a/c is cycling. When it kicks on again I'll check to set if ice is gone. I sure can't figure this out when it is a sealed unit and can not he serviced, it acts just like it is low on freon or whatever gas it is. I figured leaving the fan on would help the defrost ice but I that didn't help either.

bobbecky · 06-07-2014, 11:03 AM

We had this problem on an aftermarket A/C we had installed in a car years ago. Turned out, it was a thermocouple in the wrong place in the evaporator coil. It either wasn't installed correctly, or had dropped out after installation. Finally took it to a different shop, and the tech found it right away. Everything else was good and never had any other problem with it. I guess the thermocouple was there to sense temperature in the coils and would adjust freon flow from what I remember him telling me.

Terry W. · 06-07-2014, 12:31 PM

Thanks Bob so if I understand if I move the probe in the coil that's marked "ice" high up on the evaporator it might not ice up? The iceing does start at the top and work its way down

Terry W. · 06-07-2014, 01:06 PM

Correction the terminals the probe are plugged into are mark "freeze". I moved the probe about 3/4 the way up the coil to see what happens.

PARAPTOR · 06-07-2014, 02:48 PM

Not an AC expert, but if I read your comments correctly, sounds like you are not getting enough air flow across the coil. When you opened the vents directly into the rig versus the ducting thought you said no icing. Venting directly into the rig basically zero resistance to air flow compared to pushing air through ducts. I know you mentioned you had Good shore power, but have you tried turning off that second AC unit and see if it has any effect on this unit freezing up? Did not see in your posts any mention to it ever working correctly. Members have noted that they have founds left over construction material in the ducts. Running the fan on low would only worsen the problem. Just my 2 cents

Terry W. · 06-08-2014, 05:03 AM

Well it appears that Bobbecky is the winner. I moved the probe in the evaportor coil up about 2 inches closer to the top of coil and no ice or freeze up for the last 12+ hours. And yes I did try it with the second A/C turned off and I was running the ref. and water heater on gas just to make sure I had good power. I did notice a little iceing starting above the probe but cold air never stopped and iceing never went below probe and was gone in real short order.
Thank you all for you help

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