Ray86IROC

<EDIT OK appears to have been a sudden, bad leak I guess, thing was actually low on refridgerant, but now I can't find the leak. Any tips??? >

Dangit, I thought I had all my A/C stuff fixed, redid the whole system (well reused condenser, evaporator, and lines, but flushed them) about a month ago and all has been great until today.

On the way home today my A/C started acting up, it was blowing only slightly cool (ie warm but cooler than outside air) when driving most of the time, it would noticeably cool down properly for a few seconds (like 10-15 or so) and then go back to warmish for a couple minutes then repeat.

When I got home I popped the hood, the low side line near the port that usually gets coldish if I recall and sweats and stuff was warm and pretty much dry. The expansion valve however was sweating and pretty cold to the touch.

The compressor seems to stay running as the air gets warmer and cooler, so it doesn't seem to be a pressure switch or the compressor itself I would assume.

Hooked up my a/c manifold gauge set and the low side was at 10 psi, high side around 180ish psi. After I had redone the system to start with it was running around 50/225 or so so I guess both sides are a little low now for the temp/humidity currently (about the same as temp as for original readings), but the highside is still in range.

I kinda figured I had a leak and was just a little low on R134a, and I had a can so I threw it in. During the filling process the pressure started at 50ish psi and went down as the can drained in, which it took the whole can. After it was done taking the can in the pressure settled back down to a solid 10 psi again, high side stayed about the same as it was before as well. So basically I put a can in and the pressure didn't go up, what does that tell me?

Any ideas from the experts what kinda problem I'm having here?? Am I just really low on R134a and need more? If it was way too low wouldn't the compressor switch off and the ECM read a A/C low code and not turn the compressor back on until cleared?

Could I have some kind of sticking/bad expansion valve or something (it's new w/ the compressor and dryer a month or so ago)?

I don't get what changed, everything was working excellently this morning, nice and cold the whole trip, go to come home and warm crap... I'm about to cry w/ all this A/C work I've done and I've still got problems.

Any help greatly appreciated...

2001NBMZ28

I do home AC, not cars - but sounds like it's leaking. If it was a restriction low side would be low and high side would be extremely high. 50 sounds too high - have you checked out the AC performance chart on shoebox's site? Sorry not much help...

Plague

had a similiar problem on a mazda, turns out it was low on radiator fluid b/c of a radiator fluid leak (that was slow). Might want to check into that. not sure if it is important on these cars.

Ray86IROC

Yeah I felt the original 50ish was a little high, but it was like 91 degrees or so when I read it the first time, so it wasn't way high, but that was w/ the correct oil charge and 2 lbs of refridgerant so I figured maybe the gauge read a little high or something. I don't know, it seemed to work perfectly since then...

Anyway, I did some driving with my laptop/datamaster hooked up so I could monitor the A/C compressor clutch engagement while I was driving just now, it was on steadily for awhile w/ warmish air coming out, then it cycled on and off a couple times before it threw a low A/C pressure code in the ECM, highside pressure while driving according to the computer dipped down to 135ish, so it does indeed now appear it was low the whole time. The can of R134a I put in it must have either not done the job or leaked right back out. I guess I somehow sprung a leak driving this morning, certainly doesn't seem to be a slow leak...

I snagged some stop leak + detector so I guess it's time to see if I can find the leak, I hope it's obvious...

Ray86IROC

OK, I can't seem to find the leak. I tried the stop leak w/ the red dye detector, couldn't find a drop of red dye anywhere, no leaking that I can find. I got fed up and decided to just drain the system, and pull a vacuum on it again just to start over since I couldn't be sure some air didn't get into the system anyway. Pulled the vacuum for 10-15 minutes or so and shut the vacuum off and shut the valve to the vacuum source, and over about 5 minutes or so the vacuum readings had dropped on the a/c manifold gauge by about 50%, so I clearly have a leak. I went ahead and picked up a can of R134a w/ the UV dye in it, plus a stand alone UV dye can, I'm hoping I can spot the leak like that w/ a black light. Any other tips in finding a leak??

Is there an easy way to determine if the evaporator core is the source of the leak without tearing into the dash, and if not, exactly where does one start in getting access to it, I've never messed with one in a 4th gen? Do I get at it from the underside or topside of the dash on the passenger side??

Thanks for any help.

turbotko

Can you the charge the system with a known amount of refrigerant+dye and then suck it back down in a couple of days to see how much is leaking? If it's leaking a pound or so over a week it should be easy to spot the leak. If it leaks slower it may take a while and a couple of charges with dye to find it.

My experience with evaporators leaking has been long and hard. Some of them leak enough to get dye coming out of the evap. drains which is a dead giveaway.

If it were my car, I wouldn't pull the evaporator until I had run enough dye/refrigerant through it to see it coming out of the evap drain.

BTW, If you've recently been working on the A/C system, I'd bet you have an o-ring leaking somewhere. Just my .02

Ray86IROC

Small update, I now don't believe the system was actually leaking at all, something else is hosed, I'm thinking the expansion valve has stuck shut or there is a clog in evaporator or something.

I changed out all the o-rings in the system earlier today hoping it would be something easy before realizing something more serious was up, used the UV dye stuff as well. As soon as I put in the refridgerant charge the compressor pulls it through and starts to build pressure on the highside, but as soon as it's drained the can of refridgerant pressure drops on the low side and actually is reading vacuum on the low side, 125ish psi on the highside. Plugged 3 freakin cans in which by amount would be a little overcharged, still pulling a vacuum on the low side once it drains the can.

So I've got zero psi/slight vacuum being pulled on the low side even w/ a full charge, high side is lower than it should be (both at the highside port and according to the computer via the high side pressure sensor that is just before the expansion valve).

To me that is saying there is a problem w/ the expansion valve or a clog. But on the other hand I would have expected pressure to spike on the highside if that was the case. I'm suspecting something could have fragged compressor wise as well, guess that's what I get for buying a rebuilt unit from Advance if so...

Any insight from anyone that knows more about diagnosing low/high side pressure readings?

I'm going to try to get a new compressor/expansion valve/dryer under warranty tomorrow and just start from scratch, flush the lines/evap/condenser, etc unless anyone has some idea WTF is going on...