It's getting very warm outside.....need A/C help

[leebo]

Good deal, Droopy! Glad to help.

[nutta]

i work in the aircon/refrigeration trade just some advice to help you guys out when fixing your car a/c

most common mistake with car air conditioning is over charging. alot of mechanics dont fully understand the basic principles of an air con system. their approach to a system that isnt working properly is there must be a leak so they top up the system. an overchaged system is just as bad if not worse then an undercharged system. the best/simplest way to charge a system is to weigh in a charge. first find out how much gas the system is designed for, second reclaim the refrigerant out of the system if there is any left in there, this requires a recaliam unit and reclaim bottle. most of you will just release it to the atmosphere. then if you had the system open to change a valve or whatever moisture would hve gotton in the system you need a vaccume pump and vac out the system for about 20 mins the longer the better you cannot over vaccume a system. then get your refrigerant cyclinder put it on some acurate digital scales and weigh in the charge. start off charging with the car off on small systems the vaccume should be enough to pull the charge in without having to run te compressor. if it doesnt fully charge run the compressor and charge a vapour into the low side of the system(some refrigerant bottles have one valve some have two, single valve bottles are usually vapour only and the dual ones usually have a red and a blue valve the blue is vapour). once thats done you should be set.

you cannot properly charge a system just using gauges and charging to a set pressure because the pressure of a system is not a constant. things like heat load in the car(people) temperature of the day affect the system pressure. you can approx charge the system using gauges but it will never be perfect. if your going to liquid charge make sure its in small squirts. soapy bubbles are a good way to find leaks.

leebo when you said you charged your system your compressor locked up, you may have liquid charged the system on the low side the compressors cant pump liquid and this can damage them very quickly.

the expansion valve and compressor seperate the high and low sides of the system the evaporator is on the low side and the condenser is on the high side.

the expansion valve is what regulates the the amount of refrigerant into the evapourator it has a small oriface inside if a system will get a block this is where it will be stopping or restricting the flow to the evapourator giving no or stuff all cooling.

some systems have safety devices in them to protect them from damage most common are low pressure and high pressure cut out switch's so if your compressor isnt running when it should this is most probably the cause.

moisture is the biggest killer it reacts with the oil and refrigerant and creates acid and starts lots of preblems.

hope all this didnt confuse i tried my best to explain it in writting. air con systems are not easy to work on without the right know how and the right tools.
if you have any q's id be more then happy to help you out.

one last thing releasing ozone depleting refrigerant into the atmosphere is illegal well in australia anyway and id bet the laws the same in america so if your gonna be releasing refrigerant dont do it in the front driveway for all the neighbous to see cause it usually incurrs big fines

cheers Mitch

[leebo]

Thanks for the tips, Mitch. Just FYI, I did pull a vacuum for about 30 minutes prior to charging the system. I did the removal/replacement of the expansion valve but as for drawing the vacuum and charging the system, I did that over at a Mazda dealership where the service manager (the friend of mine) helped/showed me what to do. We didn't weigh in the charge but I agree with your points about not knowing precisely how much refrigerent you have by the pressure gauges alone. We approximated based on pressure gauge readings, temperature gauge readings at the air vents, and his general experience.

You're right in that when I originally thought I might have had a leak and just shot some refrigerent in (way before I found the true failure), it was when I tipped the can upside down and watched the liquid refrigerent shoot in through a clear tube. The compressor seized immediately when I did that, and I immediately shut the AC off. It's running fine now so hopefully I didn't do any real damage.

I have a mechanical engineering background and understand a lot of the principles involved with the AC system from school years ago, I just haven't had a lot of practical, hands-on experience with AC systems so this is an enjoyable learning experience.

Thanks again for your tips.

[nutta]

just glad to help. the way your friend charged the system is the most common way for people who know what there doing its alot easyier but would take a life time to try to explain to someone who hasn't done it before.


mitch

[scoobyEJ20]

very informitve post. i think i have the same problem. it there anyway to test the expansion value for malfunction?

if not, do you have a recommendation where buy the replacement?

[leebo]

I'm learning about AC systems but... to test an expansion valve, if it is stuck closed, then the high side pressure will be very high and the low side will be way too low. Basically, very little refrigerant will be flowing (and therefore little expanding and cooling, as well as higher pressure before the valve and lower pressure after the valve). Going off of memory, but I think that when I hooked up the gauges before replacing the failed expansion valve, I saw something around 250-300psi on the high side and 5-10psi on the low side while holding the throttle open to about 1500-2000rpm. That low side should have been more like 25-30psi and the high should have been more like 200-250psi.

I bought my part at my local dealer for around $90. Perhaps a local dealer to you will give you a break on the price.

[morphine16]

I know this is an old post but is there any one out there that may have the pics.
they dont seem to be there any more?

-Thanks

[leebo]

I know this is an old post but is there any one out there that may have the pics.
they dont seem to be there any more?

-Thanks

Take another look. I just reloaded them. Not sure what happened but they appear to be showing up now.

[morphine16]

Thanks appreciate it. im having the same problem but is there a way to like test it to make sure its the expansion valve?

[leebo]

Thanks appreciate it. im having the same problem but is there a way to like test it to make sure its the expansion valve?

Yes, you can pretty much narrow it down to the expansion valve by reading the pressures on the high and low side. I can't remember what the acceptable ranges were, but basically if the valve is stuck open, there won't be enough pressure to build on the high side (and the pressure won't drop much, and therefore cool, on the low side) when you hook up gauges to the AC ports and run the system. If you can get someone to just do a quickie reading for you (for free... it takes minutes), that would likely tell you it's acting up.

[morphine16]

Ok cool thanks for all your help man.....Its getting hotter in cali as the days go by so i need to get it fixed pretty soon.
-Thanks again

[kjb]

Hi, I'm new to the forum but have been browsing for a few years - there's some great info on here! I'm hoping someone will be able to help me. My '02 WRX has about 80k on it. Last summer, I turned on the defrost and noticed a hissing-type leak noise coming from the dash area. Over the next two days, the hissing continued when the a/c was on and it lost all cooling. I put some dye in it but couldn't see a leak. Took it to the dealer who charged me $200 to tell me that I was out of freon but the vacuum test was fine and they couldn't find the leak. Recharged the system, worked for a month then leaked again. Weather turned cooler and I didn't worry about it. Summer came again and I decided to go to a different mechanic who I'd heard good things about. After several hours of soap, dye testing, etc he also couldn't find it, but confirmed that there was a strange leak somewhere because sometimes it would hold pressure, other times it wouldn't. Also thought my exp valve was bad because when it was recharged it was still acting screwy. (By the way - great pics on here, I removed the glovebox and blower to save a little mechanic labor time. The only thing I'd add is that one of the "clips" in the back holding the white plastic part to the blower motor is actually a small screw - so it takes small hands and a double jointed wrist to get that off). Mechanic was hopeful that in replacing exp valve, he would get to see more of the system and maybe find a leak. Sure enough, he found a huge hole with dye all around it in the evaporator. Ended up replacing evap, exp valve, and the TSB for thermo sensors. It worked for a over a month and I was happy when it was 95 deg that I got it fixed. Then yesterday turn on a/c and realize it's not cold. Might be coincidence, but the last time I used it was on defrost since it was raining. It's making the "hiss" kind of noise that it always makes when you first turn on a/c, but usually goes away after a second. Now the noise continues and there's no cold air. The compressor is still kicking on so I think it's in the process of leaking. Taking it back to the mechanic on Monday, but I'm at a loss. After putting over $1500 into it with the assumption that it will be fixed, I feel like I am back at ground zero and not sure how much more I can do. Any ideas would be greatly appreciated! Is there any way that using the defrost could cause a massive leak in the a/c system? I thought maybe if the exp valve had been bad (combined with the frosting from the TSB?), the pressure built up too much and it blew out the evaporator. But with all of those replaced, what's going on??

[subaru_crazy]

^^^^Sounds like you got another leak somewhere, just because you fixed it doesn't mean another leaky spot could not appear somewhere else, or even at the same spot as previously. I would put more dye in and explore the entire system for leaks. Having said that, I posted up here before becasue my system would do the same, every 3 months it would run out of steam, but I could not locate the leak anywhere. I did put about 2 cans of leak sealer into the system and while at first it improved the time between having to recharge the system, it looks like the leak has been sealed completeley since last time I had to add coolant was last year summer time, and this year its still blowing cold without adding any. Again, you can try adding some leak sealant like I did and recharge the system to see what happens, if it improves but runs out add another can and maybe if its a tiny leak it will seal itself. If not you'll probably need to tear up the system and fix it again.

[djinn23]

I'll report back once the repair is complete.

Just wondering if you completed it and how it went

[fishfry]

Same problem, clogged/broken expansion valve. Took car to auto shop to get system evacuated, replaced valve with non-OEM one ($16 vs $100) and took it back to get the system re-charged again. In total I saved about 300 dollars!

The replacement was not that hard, I had a hard time getting the electrical plug apart in the glove box. You have to push the tab down on the outside and it doesn't bend easily. Pretty awkward working in this part of the car, but the disassemble and reassembly is not that bad. I did not need to bend or tweak the metal connection in order to get the blower assembly out.

Thanks again, this thread helped a lot!