a.c. help

bingo

not enough freon in it

this lowers pressures, which lower evaporator temp, which causes freeze-up

Thanks.

Has anyone ever tried a product called freeze12? A coworker used some instead of converting his a.c system over to r134a. It is supposed to be compatible with r12...

TIA

+++++++++= I think Mr. Trans has been drinkin tonight....Not enough freon so it cools too good? Sounds to me like you need to check that drain one more time and then check the cycle switch, sometimes known as the low pressure switch. It could be stuck closed so the poor thing wont cycle on and off. The switch is located under the hood on the accumulator. But, before you do that make sure it isnt just blowing air out the defrost or heater vents fooling you into thinking its not blowing air at all. Now that I think about it I dont ever recall a Chevy freezing, nor a cycle switch sticking closed. They will fail the other way. Must be a problem with the air going to the wrong place......

yes

learn something about how it works before you make a total ass of yourself, OK ?

I'd do a conversion before dumping any of the so-called 'compatible' replacements into it.

GM's convert pretty well, Fords do too. Mopars not so well

Even if he was drinkin', he's still right Scott. A/C systems cool the best at extremely low, low-side pressures. A leaking A/C system will get colder before it just quits working altogether. The secret to getting an A/C system it's coldest is to run it as low as possible without freezing up the evaporator core or prohibiting it from running via the low-pressure cutoff switch.

My old Acclaim would "snow" out of the vents when she was getting low (had a small leak I never did find, just topped her up every 2 months or so) and the evaporator was starting to frost up.

Doc

""Doc"" wrote in message news: snipped-for-privacy@adelphia.com...

Sorry, but I think you both have been drinkin:) An Aclaim? That's an old Chrysler product isnt it? That system is WAY different than a Chevy. It used a temp controlled expansion block and a low temp cut-out if I remember correctly. If the low temp switch stuck closed they would freeze up in a hurry. The Chevy has a fixed size expansion tube and is made to work at the correct freon level, (liquid going through it) Like I said, the only way it would freeze is if the cycle/low pressure switch was stuck closed. If the switch was working correctly it would cycle like crazy and never get real cold. BTW, I dont think I have EVER seen one stick closed, open yes, closed no. I know how A/C systems work, and I know what you mean about the the lower the low side is the better it will cool but....on the Chevy if the low side is so low that it cycles too much it means its low on freon AND it wont cool good. I have never tryed bypassing the cycle switch long enough to see if it would freeze but I guess it's possible if the outside temp was low enough (or the inside temp if its set on MAX). You must remember that if it is low on freon or not, and gets cold enough to freeze the problem is the cycle switch not the freon level. Either way I think his problem is most likely the air is going out the defrost and not the vents, making him think it is freezing when it isnt. Just for the record trans dude, I know exactly how A/C sytems work, and I think your reply was based on general A/C physics, I guess you could say, not the specific system in the truck. No?

keep digging, kid

we enjoy know-it-alls like yourself, you provide hours and hours of cheap entertainment

SURE you do

HAHAHAHA

Wrong

It's based on seeing GM systems freeze up in:

91 GrandAm 87 Bonneville several GM trucks (the 'oh, while you're doing the transmission, can you see why my AC quits working after a while' thing)

in all cases, the low-pressure cut-out was working...........when evap temps get down to 10 degrees or so due to low charge, it doesn't take much compressor operation to keep it that way.........and on a humid (90 % +) day here, it'll freeze up in about 10 minutes

The air is not coming out the defrost, floor, or from anywhere else in the cab as far as I can tell. I thought about a faulty flap or a possible break in the air duct, but all that seemed fine.

I had a new cycle switch that I never used for my sister's truck so I tried that while I was tinkering with it, and it did not change a thing.

I had bad luck in the past converting to r134a. I think I have some r12 somewhere, hopefully. I always watched/let my father charge a.c. systems. But he passed away recently and I inherited the tools, so I might as well as learn how. If I blow it all up, then I will definitely convert :)

Thanks for the help, yall! Hutch

Even houses with central air will exhibit the same freeze up symptoms when the Freon level is getting low. So I guess that Mr. Scott M needs to find out for us it that's a GM system or a Chrysler system!

LOL!

Brian

I've charged up plenty of Chevy trucks and I don't recall even one that would freeze up due to a low charge. Usuall complaints are either that the clutch cycles too often or that it doesn't cool well. I'm sure a low system could cause a freeze up in some types of systems.... but one using a low pressure switch should not freeze unless the switch is bad or not adjusted correctly. Bob

Just so you know, I'm not a "kid". I've been working on A/C systems for about 20 years. I dont know where you live but here in CA I dont ever remember a Chevy truck with the simple low pressure/cycle switch system freeze up. I guess it's possible in a VERY humid climate, but I sure dont remember seeing it here. It doesnt get that humid here very often, sure as hell not 90+ percent. The only systems I've seen freeze up are on hondas and the like that have a temp controlled expansion block and a temp controlled cycle switch that didnt open when it got to cold.(kinda what happened to Doc on his chrysler I suspect) I dont really feel the need to argue with you, I can just tell this guy with the problem what I have experianced. Just out of curiosity, what are the pressures like when the Chevy trucks youve seen freeze?

low-pressure

========= Yep, did two today: A late 80's Ford pickup, this had a system like the Chevy, a low pres switch on the accumulator. The complaint: not cooling very well. Stuck the gauges on it and guess what? It was low. The compressor cycled too much. Added about a pound of R12 and it cooled great.....The other was a 91 jeep cherokee. It had the expansion block on the firewall. The complaint: barely cools. Guess what, It was very low. Slowley added R12 and it got colder and colder. BTW it was about 90 deg. today. As far as systems on a house I'm not familiar with but they have to have some sort of expansion tube and pressure switches just like cars. I bet there are different systems just like in vehicles. Why not tell me exactly how they work Brian? I would love to hear it from an expert. If you can discribe it, I can tell you the similarities to vehicles. I still would like to know the high and low side pressure on these Chevy trucks when the evap freezes.....Anyone?

Two autos so far this spring doing this. One was a '91 Cadillac Fleetwood Brougham, and the other was an mid-'80 GMC pickup. Both were R-12, and hadn't been converted. I don't have any written figures and I am not going to look up the W.O. but the low side on both was somewhere near 20-25psi. Just the right pressure/temperature to still cool, and freeze up. The sure sign of a freezing evaporator is the reduced output of air. Because an R-12 system at 20-25psi is in the 20ºsF, moisture freezes on the evaporator fins as soon as it condenser's. This builds up fairly rapidly and prevents the air from passing through the unit and thus stops cooling the car etc. There is just a small range of pressure where the entire evaporator will freeze over. It usually occurs right after a system starts leaking and the low side pressure drops into the 20s psi. As more freon leaks out of the system less and a less of the evaporator is cold enough to freeze, then you have the system blowing plenty of air, but it isn't very cool.

My work is on boats/yachts/motor homes/campers/ice machines with some autos and a 28 beach rental units. Freezing around the ocean (high humidity) is very common. It only happens with units that have a very, very small leak. Just the kind of leak that is next to impossible to find and fix. I have also seen it happen on Ford and Chryslers Auto systems. I don't know about rice-burners as I don't work on them.

I am not the worlds greatest expert on anything, but I know that the surest way to be proven wrong is to make a statement that something is impossible.

first off, your 'not seeing it here', when 'here' is CA, is WHY you have not seen it

in wwestern IL in summer, we have 80-90% humidity foir days on end

pressures ? 20-30 low side, low 100's to mid 100's high side

rapid cycling with evap temps in the high teens to low twenty's

it will freeze up in about 15-20 minutes, ESPECIALLY if there is any dirt, lint, or other 'stuff' stuck to the coil to give the frost a place to start

>

low-pressure

================ Yep, that must be it. A combo of relatively low outside temps and very high humidity. We rarley see humidity over 30 percent.

I used to live out in San Jose and have fond memories of the dry heat. Here in NE Ohio, we'll hit humidities in the 90's for days at a time. So damn humid outside you have to change your drawers after every venture outdoors. The only time I've had an Evaporator freeze up and snow out the vents was in weather like this, never in the dry heat.

Doc

>

Well it's like this Scott, I'm not an expert and didn't claim to be. But I do own a house with central air and have had ac service performed on it twice in the last 20 years due to the condenser freezing up. The cause you ask? The service technician both times added Freon as it was low. And guess where I live? Cincinnati Ohio where it gets extremely hot and humid. As Doc states in his post below, he being from NE Ohio where we share the same weather patterns in the summer. And as you have admitted below just because it doesn't happen in California where it is dry, doesn't mean it can't happen. Correct statement?

I go to Chino for my company about 3 times a year and then visit my son who lives at Hermosa Beach. So I know the weather is very dry compared to Ohio.

Brian

If I'm not mistaken, isn't the low pressure switch on a Chevy truck supposed to open at about 38PSI? Bob