A/C Freeze Up

[Norquist]

My 2001 C/C air conditioning seems to want to "freeze" up. Meaning ice is accummultating on the condensing unit (I presume) thus not allowing air to flow over it. I have to shut the A/C off for a few minutes so it can thaw out then turn it back on.

I'm not keeping it like a meat locker, outside temp comming home from Sturgis yesterday was mid 90's, low humidity, it happened twice.

Any suggestions, or anyone else experienced this??

[GreyPower3500]

So far I haven't actually had the a/c ever STOP supplying cold air completely. I suspect the evaporator's been partially blocked by ice during high humidity/temp operation --- this is judging by the cup or two of water that drains out in my driveway after I've shut down at home !!!

I do, however, this issue of freezing and surplus of water holding onto the evap. has a WHOLE BUNCH to do with why my truck stinks like a mouldy Florida basement...

Dealer's done this "spray deodorizer kit" nonsense into the evaporator twice without correcting the problem. GM's brilliant idea to correct this was to supply an "afterblower" kit that cycles the blower fan on "HI" setting in four or five second bursts to blow the water off the core after you shut the truck off. Might have helped on my truck if they'd done it sooner --- but now I suspect the core is too polluted for it to help... The problem is GM's own creation: in the interests of saving space in the cab (and money, of course) the manufacturers have mashed more fins/tubes into a smaller evaporator, and it can no longer shed water properly, BUT makes great mould!

Back to your request (now that I've had a chance to rant! Sorry...): IIRC, selecting "recirc" will pull the already cooled, dehumidified cabin air back though the core and should correct things. If it's still freezing while in "recirc", have your dealer make a complete check of the a/c system on your truck --- might simply be a plugged drain on the evap. tray! Best of luck.

BTW: I'd be excited to hear from anyone who's had the mould issue properly resolved and how/what they did !!!

[gardnerteam]

This was a very common problem on 6.2 and 6.5 trucks, but haven't heard of it on D/A until yours. I never found a cure for it on the old trucks. Hope it never happens on my D/A. Used the AC a lot in Mexico and Az, and no problems yet.

[ram/tx]

Norquest... Just made a trip to W.Va. and mine froze up at least 4 times going up there and back. I could feel it when it did it. All of a sudden the air coming out of the vents wasn't as cold as before. I would stop for awhile and a bunch of water would drain out of the truck and then the AC would start putting out good cold air again. The wife even got a couple of drops of water on her feet and ask me why, I didn't have the heart to tell her the new truck AC was freezing up. I plan to take it to the dealer and let them look at it. They will probably say they could not duplicate the problem, it works fine as long as you only drive it a couple hours at a time, but on long hauls it will freeze up.

[nukedmax]

GreyPower3500: Years ago, I used to service Auto A/C.

This is usually two different problems: On all machines I worked on (and I assume, this one) there is a low temperature cutout switch. You allow the machine to idle, set the fan to low and put a thermometer in the outlet closest to the evaporator. You set the low temp cutout to turn off the compressor at an air temp of 35-38 degrees. This will keep the evaporator from rocking up.

The other problem is usually some blockage that keeps water from draining completely at night. Once you have mold, it is very difficult to get rid of the problem.

Since other people have not complained about moldy A/C, I assume that it is not a problem generic to these trucks (the humidity is low here so we normally won't have the problem). This implies that there is something unique about your truck. In the old days we went so far as to install an extra drain in some Mustangs. If you can get it to drain, you can cure the problem. Good Luck.

[mackin]

Since we on the subject......How come when I have my truck on recirculation without the ac button in (illuminated) I get cold air like the ac is on? I can hear the compressor cycle too......Ac works fine when on (colder)......When its in the fresh air position it works like a vent.......my assumption would be it would ONLY recirculate the air in the cabin not change the temp......The manual states MAX air is ,Ac on in recirculation selected,when cabin is adequately chilled select fresh air.......Or something like that.....

MAC

[Paintdude]

does being low on freon make a system freeze up??

Just a thought..

Could the intake of the cabin air be obstructed? Plastic bag, leaves, etc?????

[ 08-12-2002: Message edited by: Paintdude ]</p>

[nukedmax]

Paintdude: If you are low on Freon (even though it is not freon anymore) the compressor will pump the system down until it trips on low suction pressure, It will soon restart and trip again. The effect you notice is that the A/C seems to work ok until it gets hot outside then it seems to warm up.

Even if the inlet was restricted, the compressor is supposed to cycle off when the core gets down to a preset temp. (above 32 deg).

[letsgo]

Its like (nukedmax) says your low on freon or FM200 any time you see an ice buildup in the summer time.

[Paintdude]

I just remember when the low side would frost up, it didnt have enough gas (R12 back then) in the system..I just assume the 134a is the close to the same...

Here is a post from another board..

Yesterday, my Air Conditioner started to act up. What its doing is not blowing hard when set on high. Up until earlier yesterday if would freeze you out. It still sounds like its blowing hard but its not comming out of the vents hard. Its almost like something has partially blocked the duct work or something. Any ideas?

then a reply..

Check the blower intake for obstruction. This happened to me. It was a small plastic bag that had gotten sucked up. Its right above the floor on the passenger side. Feel for it with your hand under the dash.


Then the response..

Thats exactly what it was. A plastic bag had sucked up to the intake and blocked it. Thanks.

[Tommy turbo]

My dmax will go 100 miles then gradually start blowing less air and warmer for about five miles then come back strong for another 100 miles. Changed filters, looked for restrictions, checked refrigerant charge, etc. looks as if evaperator is freezing up. Had in to the dealer for updates and listed this complaint on worksheet. Service writer said upon completion could not replicate. I said i am glad you did not test drive for 100 miles but is there no other solution? He had no answer for me. But it is documented. thanks.

[Paintdude]

I also noticed that the 03 duramax does not have the mufflers on the a/c lines at the compressor like the 01 and 02's do..

I thought this was to make for no load compressor starts..Like water hammers in a plumbing system..

could account for a lower amount of refridgerant in the system??..

[stretch]

I not an auto a/c pro but on residential and commercial building applications, low refridgerant will cause the evaperator coil to freeze. On automotive applications, there should be a low pressure cut-out that prevents this, that is what I would check first. then I would put on the gauges and check the operating pressures. Another thing to check is the filter, low air flow can cause freeze up's also. BTW, how did you determine it was frozen ? If you can see the evap coil, try to get some evap coil cleaner sprayed in there, It will help get rid of the dirt and mold. :cool:

[Norquist]

NUKEDMAX do you know where the location is of the
low cutout on the Duramax? I can do what you explained if I know what to adjust. Sounds like a simple logicial solution.

[Norquist]

GREYPOWER3500 The first time it did it i was in recir. So thinking that it was just too cold changed it to fresh intake (after shutting it down for a few minutes) and it did it again after a while.

[CSDMAX]

Mackin,

"How come when I have my truck on recirculation without the ac button in (illuminated) I get cold air like the ac is on? I can hear the compressor cycle too.....my assumption would be it would ONLY recirculate the air in the cabin not change the temp.."

I have noticed the same situation, but I have also noticed that if you have it on vent only, and then switch to recirculate(without AC) it blows cabin temp air. If I switch to AC and then to recirculate it continues to blow icy cold air as you have indicated above. I have asked the stealer about it and got the usual lame duck answer. This is not the same setup as I had with my 97' CC. When it was on recirculate that what is was RECIRCULATE! Not AC blowin..probably CA tree hugging..cr.. :D

Don

[Paintdude]

the only way for the dealer to know if the system is low on Refridgerant or not is to, evacuate it all out,capture it, measure it and refill the system to the recommended amount....

[nukedmax]

Norquist: I stared at the A/C for a while but was hesitant to adjust anything without a manual. Whenever we can get some !@#$#$ manuals, this will be an easy fix. One question I don't have the answer to is: The dealer service department has to know this and should have already ajusted it (standard procedure). Did they not do the work? Is it at the end of its adjustment and should be replaced? Don't know.