car air conditioner compressor questions

[tercel89]

We have a 2000 Mazda Protege that has 233,000 miles on it. We have owned it since new. It has been babied . I am a pretty good mechanic but I dont know that much about air conditioning.  The A.C. has been blowing warm lately. I charged the system last night and it didnt do any good. I now am looking at the compressor and see that it turns on and off a lot . Like the clutch is engaging and disengaging frequently too much instead of just staying on  . Could this mean that the compressor is bad ? Any help is appreciated. 

[TripleDigitRide]

That often means it's low on freon. You may have a leak.

Edited May 31, 2013 by TripleDigitRide

[ted]

You may not have enough freon or to mutch freon what does your low side gauge say and high side say is it a 134a sys low side on 134a should read about 40 psi High side should be about 275 to 280 if your low side is below 40 and your high side is above 325 then you may have a restriction poss expiation valve ,if your high side is about 200 and your low side is about 30psi it does not have enough freon. It will also cycle on and off a lot if you have to mutch freon. Because it is building up to mutch head pressure. Edited May 31, 2013 by ted

[glock55]

The following questions need to be answered before any conclusions can be reached: 1) did you use gauges to recharge or just a can and single hose? 2) did the system have any freon in it when you charged it? If not there was air in system and must be evacuated before charging 3) did you see any oily areas on any a/c components these would indicate possible leak sources 4) is your engine fan turning at a good speed or not free wheeling as this will cause high head pressure 5) fast cycling can be caused by a bad clutch or defective switch in the system 6) if the system was out of freon the desiccant pack will be defective also and receiver/dryer will need replacement 7) a way to rough guess freon charge is to hook up gauges, pressure should be about the same as ambient temp, if ten pounds or more above ambient temp is overcharged or has air in system,if ten pounds or more less than temp is low of freon. If your system has never had any work done to it may have had low freon charge due to seasonal leakage. An evac and recharge with correct amount of freon is the starting point for diagnostics. I can send a/ c troubleshooting guide and gauge guide to assist you if needed. A/c repair is not really a backyard job if one doesn't have the correct tools. Good luck

[tercel89]

SO far after reading this and reading about AC units in general , it seems I am gonig to have to evacuate the whole system then add coolant. I have read several things about how people will just atempt to add coolant and it wont work becuase all the coolant should be evacuated out then new coolant added. 

[glock55]

If you plan to evac the system with a gauge set, pull a 30 minute evac then close both gauges before you turn the vac pump off. The low side gauge should be around 30 in vac and Should hold this for 30 minutes. If system does not hold vac you have a leak that should be repaired. Trace all lines and components for oily spots that will indicate a leak. If system holds vac hook freon can to hose and open can. Open the line on the can where it attaches to gauge set until freon comes out. This will get the air out of the hose before charging. Remember it's better to be slightly under charged than to over charge the system. Good luck

Yes it usually doesn't fix the system just to add freon due to fact that they wind up over charging or there is air in system. Edited June 1, 2013 by glock55

[Sam1]

Ted hit it on the head, it'll cost $20-$30 just to refill if you buy the stuff yourself, might as well spend a few extra $ and get it done right.  Last time we did it at a shop it was only like $49, just keep your eye out in the newspapers for coupons at local shops they usually run specials every week.

 

PS don't charge the system if you think there's air in it.  When we were doing a motor build I unhooked the system and plugged it back up, forgot, turned on the AC the next day and blew a couple of hoses off, the guy at the shop said that air doesn't compress and pressure in there can hit 600+psi easily and do some serious damage

Edited June 1, 2013 by Sam1

[Guest 6.8 AR]

You might need to replace some parts in the system, like an expansion valve, or orifice tube. With that many miles

and seasons, the wear and tear on the compressor could have clogged the expansion tube or valve. Of course, with

it cycling too fast it could be building pressure too fast and not moving through the system. Condensors will clog up

and cause that, also. That dryer should always be replaced if the system is opened.

Edited June 1, 2013 by 6.8 AR

[Dad03]

I have a '95 Volvo 850 that is my road beater to and from work. It did this too. Turns out the compressor needed to be shimed. The flywheel was out of spec, meaning to far away from the magnets to stay engaged. A few 3/8" washers and some JB weld and it was enough to position it back to where the magnets would hold it. Been working like that for 3 years.

 

You may also want to check you pressure switch to be sure its not faulty.

[tercel89]

UPDATE: My mother-in-law's friend is a retired mechanic. He tested it today with all his biog stuff and fancy gauges and all. It has no leaks. It also has plenty of coolant too. He said that the coolant isnt circulating properly like there is a restriction in the loop or system. He told me to start with the drier and then maybe the expansion valve. We will empty out the coolant and pressure then put in a new drier and then maybe a new expansion valve. 

[gnmwilliams]

Just had to replace my wife's compressor. Everytime you turned on the AC it would blow warm but the car would also stutter and try to stall and then the engine would start over heating. Turned out to be a bad compressor and a bad condensor fan. They seemed to think that the bad condenser fan could have contributed to the compressor failing because it was working to hard due to overheating.

[Guest 6.8 AR]

That's good to know, Tercel. My bet is the expansion valve, but condensors in small cars have a strong

tendency to clog up as well. I wouldn't bother flushing it, either. New ones are at Advance or Autozone.

Expansion valves just get replaced, also. I gutted my Focus when I did it. It's all new, and I don't even use it.

[tercel89]

That's good to know, Tercel. My bet is the expansion valve, but condensors in small cars have a strong

tendency to clog up as well. I wouldn't bother flushing it, either. New ones are at Advance or Autozone.

Expansion valves just get replaced, also. I gutted my Focus when I did it. It's all new, and I don't even use it.

The only bad thing is the expansion valve is WAY UNDER the dashboard and air bag !!!! DARN IT !!!! and the drier is a whole lot easier to get to . 

[Guest 6.8 AR]

But the drier won't fix the problem alone. If it's the valve, ya gotta do what ya gotta do. You're going to have to break

the system anyway and if it is worth it, I'd go ahead and replace the valve and condensor, pull the vacuum and charge

it up. At least the condensor part is easy. If you need a flush canister or any other stuff I might have, you're welcome

to use it.

[glock55]

UPDATE: My mother-in-law's friend is a retired mechanic. He tested it today with all his biog stuff and fancy gauges and all. It has no leaks. It also has plenty of coolant too. He said that the coolant isnt circulating properly like there is a restriction in the loop or system. He told me to start with the drier and then maybe the expansion valve. We will empty out the coolant and pressure then put in a new drier and then maybe a new expansion valve. 

if the system has a restriction the low side gauge should have gone into a vac or have been very low with the system running. if you decide to change the txv be sure to look in the valve for any debris. if you see any pellet type substance the dissicant pack in the dryer has come apart. if this is the issue be sure to flush the system or you will have a repeat of the problem. also change out the dryer. when you recharge you can charge through the high and low side with system off but only charge through the low side with system running. good luck

[tercel89]

I just dont know how in the heck I am gonna get all the underdash board crap out of my way. It is so much crap packed into a small a$$ area!!!!