Off Topic, ? about Auto A/C

[TopCatGr58]

Hey there you Auto techies,

I've got a Chevy, 94 Corsica with factory air, been great for 10 years, recently tried to use it, and only room temp air. Also didn't notice the engine drag when turned on like it used to. Checked under the hood, with engine running, turned the AC switch on, fan starts blowing inside the car, but I can clearly see that the Electric Compressor Clutch is NOT engaging!!! It's just free spinning like it does when it's turned off.

Since the inner fan is blowing, can I rule out a FUSE? Can I check this clutch with jumper wires to ensure that it's the clutch mechanism and not just a short in the wiring going to it? Thanks in advance for any pointers!
T.C. getting hotter under the collar everyday!!

PS, not much action in the FORUM, must be great weather across the country and everybody is out riding!!!

[beechfront]

hey topcat -

could be any number of things. most likely though, you are low on freon. there is some kind of sensor that will prevent the a/c from kicking in if freon levels get too low. this is to save the pump. by law if you take it somewhere they are required to search for annd fix ($$) the leak. many mechanics though will just re-charge your system. i don't think it is such a big deal now with the new freon.



or - as was the case with my car 2 weeks ago - i had a broken wire going to the a/c. fixed that and it's good as new.

[rover]

Usually the cause for this is not enough freon in the system, lowering the static pressure below the point where the clutch will be switched on. I'm not sure if a 94 has 134A freon in it, or R-12. If you are lucky, it will have 134A which is readily available. Depending on where you are, it may be sold in stores such as Wal-mart. R-12 has not been manufactured for several years, is very scarce, and therefore expensive. If you have R-12, your system can be converted over to 134A much cheaper than refilling it with R-12. There should be a label somewhere near the fill valve if it has 134A. Hope this helps. Look up Auto Air Conditioning with your search engine, and you will get a lot of information on how AC works, and how to recharge it. If you have a wiring diagram, you could jump the clutch circuit, get the compressor running, let it build up pressure, remove the jumper, and see if it will stay running. If it does, then the freon charge level has diminished to the point where there will not be enough static pressure to operate the clutch solenoid. Do not leave the jumper in place much more than a minute, cause if the charge is low, so is the oil that lubes the compressor

[JohnSg]

Usually on the radiator fan cowling is a label that shows how the serpentine belt is threaded. On that label should be the information about the refrigerant type and charge weight.

If you are low on charge, be sure to add refrigerant ONLY to the low pressure side as many injuries and even fatalities come from improper charging.

[sksxs1100]

there is a low pressure switch that stops the compressor from engaging when low of freon.

[TopCatGr58]

Chilling Update!

Thanks everybody!!!

I first found and checked the wire going to the clutch, no power/voltage sensed when switch was on, but that as you all said was probably due to the low pressure safety control. I jumped it from the battery, and it clicked in place, which allowed me to charge it, it was already 134 and I had bought a kit a couple of years ago, and had done a check slight charge of it then.

It took almost 2 cans, so it was apparently totally drained!? Now to the why. After charging it, the AC was blowing quite chilly!!! After I disconnected the charging lines, and put the blue plastic cap on, I then turned the car off. I then noticed that I was still hearing the sound of gas escaping! I opened the hood, and it was emminating from the low side valve. I removed the blue cap, and it was leaking, apparently a slightly damaged ?Schraeder? type valve, so I put the bluc cap back on which had a rubber oring seal is the top, and really torqued it in place, and the leaking sound stopped!

So, that's most likely where and why it leaked out, hopefully that cap will keep it sealed in. Many thanks to all who responded.
Hey, like we all say...."No Sweat.......literally! "
Top"Cool"Cat ! ! !

[Czekus21]

Don't trust the cap to keep the refer in. It will leak back out. When it does, and the system is drained you may want to replace the valve...OR... Take it to a shop that does this kind of work. BUT, make sure that they don't do anything without your approval first. Alot of shops will explain stuff in shuch away that by the time you drive outa there your car has been totaly restored and the bill outta this world..

[beechfront]

also - i've been told that unless you are using the proper guages, etc..... you can damage your a/c pump.

[JohnSg]

Two cans is a lot of freon. Too much can cause the system to shut down on high pressure. How many ounces were in the cans? What did the label I referred to earlier say was a full charge? Did the stuff you put in have oil in it? When you lose refrigerant, you also lose compressor lubricating oil because it is distributed throughout the system with the freon, though most stays in the compressor. Don't want to sieze up the compressor due to lack of lubrication, then you're really talking an expensive repair!

If you lose this charge, take it to a service center because you'll probably have lost the vacuum too. All leaks will have to be repaired. The system has to be pulled down to about 500 microns of vacuum to be sure it is free of moisture before it's charged with refrigerant.

[Jerry]

FWIW, another way to check the system if pressure is low is to remove the wiring on the low pressure switch and jump the contacts with a wire or paperclip. (Wire-side connector has 2 female connections.) You don't have to worry about a jumper wire off the battery this way. Compressor will come on with the A/C switch. (Fan must be on level 2 or higher.) Don't run long this way; refrigerant carries lubricant for the compressor. No refrigerant, no lubrication.

[TopCatGr58]

Hey JohnSG,

The capacity is 2.25 lbs, the cans were only 12oz each. That valve looked like it was a molded part of the hose that connected to the evaporative core...right behind the engine next to the fire wall, kinda tough to get to. Since it was leaking even when I pulled the filling hose loose, I didn't take a long time to look at it too closely! Do you know if they can be fixed, or will I probably need to replace the hose/valve complete!? The cans were refrigerant only, no oil! I guess I'll probably end up taking it to an AC shop if it doesn't hold so it can be vacuum filled as well as fixed!?

I may have to endure the "all season" type of AC depending upon the pocket book?! Thanks again everybody!
T.C.

[JohnSg]

I'm not sure about your particular model but there are usually two Schrader type fittings in the system, one on the high pressure side and the other on the low side. The OD of the fittings are different so you can't/shouldn't be able to screw the filler adapter onto the wrong one. Special fittings on guages for R134a fit these valves. Since you added 24 ounces of freon to a system designed to run on 34 ounces, you "should" be OK for a while.

If the valve is leaking as bad as you say, the system was probably empty, moisture has entered the system and it won't hold freon for long. I'm afraid the hose with the leaky valve will have to be replaced. The system should then be pressure tested with nitrogen and soap solution to check for any more leaks. If nothing else seems to be leaking, next I pull down a vaccuum and let it sit over night with guages to be positive. Then refrigerant can be added again. If not 100% confident no more leaks, or time doesn't allow, refrigerant with UV dye can be added.

The refrigerant is what cools the compressor and the lubricating oil circulates through the system with the freon. The oil pressure/level should be checked too since the compressor is by far the most expensive component in the system.

I know it's a tough pill to swallow, but air conditioning runs at a delicate balance (sorta like fuel/air mixture in XS11s) and unless thoroughly knowlegable in AC, should be taken to a reputable AC repair technician. I don't normally work on automotive AC but believe working pressures should be tested with the engine running at 2000 rpms.

I'm an electrician in an auto assembly plant and started HVAC school a few months ago because my new job assignment calls for me to work on the Mammoth AC units (still R-12) on the roof. I'm on vacation for the rest of the week and my books and charts are at work or I'd let you know what the nominal high and low side working pressures should be. Don't know them from rote memory yet. By October, I should be high pressure, high capacity certified.

Good luck!

[graybird78]

ac problems.

hi t.c and to all. sorry to here about your ac woes. i work on cages for a living so hope i can help you out. much info posted is correct. you state your car is a 94. ac system could be r-12 or 134-a.these refridgerants are not compatable. there should be a tag under the hood to indicate which system you have. easy way to tell the two apart is r-12 has screw on fittings r-134a has quick disconnects that are a different size. high side is smaller of two lines low side is bigger of two. as stated earlier you can find what is referred to as a low pressure cut out switch. low pressure cut out switch is designed to disrupt the signal going to compressor so the compressor cannot ingage. low freon means low oil - bad for compressor. to verify compressor function you can find a low pressure cut off switch, which in your case can be located on the receiver dryer. it looks like a big silver can with steel lines going into it. un-hook the connector and you can use a paper clip or piece of wire to cross over the 2 connections and you should hear the compressor ingage. this is an indication that either the freon level is low or you have a electrical problem. if your system was originally fitted with r-12 and has been converted over you can not refill the system with amount shown on the factory re-fill tag. r-134 carries higher head pressures than r-12 so it requires less freon to fill the system. you should always re-fill the system on the low pressure side - which would have a blue cap if it's r-134a or the easy way is to look for the big a/c line. that's the low side. if your car holds 2.25 lbs of r-12 i would suggest only filling it with 2 lbs of 134a. 12 oz. cans are not considered a pound. as to your question as to replacing the shrader valve on the low side they ARE replacable with a special a/c tool that you can purchase at most auto part stores. it resembles a tire valve core removal tool but may be bigger in size to accomidate the shrader valve size. the only time you should have to vacuum the system down is if the system has been opened to remove air. otherwise all you have to do is just fill they system. another easy way to check for any leaks is to get a spray bottle, fill with dishwashing soap and water and spray the hoses, compressor and fittings down. just watch for the bubbles. you've found your leak. would highly suggest that if the system was NOT working and is NOW working to try to purchase some 134a that has oil in the can. you can also buy cans of oil to re-charge systems. also try to locate some freon with dye already in it. to charge system start vehicle, put a/c on max a/c, open valve on can (or whatever you're using to charge the system) turn can upside down to charge. if you're having a problem getting the system to take the freon try putting the can in warm water while charging. it's kind of hard to estimate using cans to charge but most of the time it's a safe bet that a system still has SOME freon in it so 2 cans of freon would be about right for system to be full. if by chance you're using some a/c gauges your pressures would be between 35 & 50 on the low side, 225 - 350 on the high side. outside temp and humidity plays a big part on your pressures. also, check between your radiator and a/c condenser to see if there's any foreign material, leaves, bugs, rocks, ect... if so use a garden hose with high pressure, to spray out. this can also help the performance of your a/c. ramble ramble ramble...

so with a little bit of time & effort, most of you can charge your systems at home. so i'll quit rambling for now - hopefully this helps you out - sorry to rant for so long
graybird78

[TopCatGr58]

Hey again JohnSG and Graybird78,

Thanks for the input, it had R-134a originally in it. Manual says it will hold 2.25lbs of R-134a It was working fine about 1 week ago, although it did seem like it wasn't getting as cool as fast. So apparently with the increased heat temps we have had lately, that schrader valve must have gone completely, and so it all leaked out, and after my little charging session, it has already leaked out again!!

So, now I can inspect that valve without fear of loosing anymore freon, and see about being able to repair it!? I wonder if the local auto parts store will carry this part, or if I'll need to go to an Auto AC shop, and whether they will even sell it to me!?

The directions on the FREON cans said to keep upright, and the system took in the freon, I just occasionally shook/swivelled the can around, and I could feel the can get cool, which told me there was still freon in it, and when it no longer got cool, that's when I knew it was empty and could switch cans. I still have 1 full 12oz can, yeah, I know it takes 16oz for a pound. Don't know if I can find anymore, plus some with oil/sealant as well. My recharge kit does have a gauge to show filling pressure, but not able to apply vacuum or check oil amount!?

When it had freon after this last charge, the compressor did kick on when I switched the AC on, so that's what it was, just low on freon. I'm pretty sure that the low side schrader valve was/is the only leak it had! I'll look into the repair option vs. what the AC shop will charge for repair/leak inspection and recharge!?
Thanks again for all info and help. Thankfully I'm from Fla. so I can handle the heat a bit better than SWMBO, but she has her own NEW SUV....I got stuck with the 10 y/o hand me down!!
T.C.

[TopCatGr58]

Final Update!

Hey there all of you "cool" folks,

Just wanted to post a final update on my success. I first found the replacement schrader valves at the auto store. I then had to go to about 5 different stores, auto, Walmart, hardware, trying to find a valve core tool, finally found an actual one for Auto A/C, of course that set it at a premium price of $12.00. Then went and got an R-134c conversion kit, which if I had gotten and opened it up first, could have saved me the $ of the valve core, it had extras in it as part of the conversion hardware, also had 3 cans of 15oz ea R-134c coolant/oil/leak sealant combined, and inline gauge, all for only $30.00 at local wholesale shop.

Switched out the valve, fired up the car, bypassed the compressor clutch switch to get it going, connected the coolant/oil and put 2 full cans in it! When finished was just below the 45PSI level, and the air was nice and crispy cool coming out of the vents in the car. Removed filling hardware, turned off car, and NO ssssssssssssss was heard!!! Put new blue seal cap on, and viola, was done in less than 30 minutes, not counting the hour plus shopping for the parts!!! Many thanks to all!!!!

Top "cool" Cat for sure now!