Is this A/C shop trying to screw me?

[Badger]

recently took my CSX to my local A/C shop because cold air (R12) was no longer coming out and I had the system recharged and dye put in it less then a year ago. After the system was tested and checked for leaks he told me he couldnt see the dye anywhere and couldnt get back under the dash where the evaporator is the leak must be at the evaporator.
Isnt there some way of verifying this (like pressure testing the evaporator or something) before I take the time and effort to tear apart the dash without 100% certainty that this really is the problem?

[csomni]

you can psi test the evap. you have to isolate it from the system. or you can try a electronic feon tester . by getting it as close to the evap as you can. if it sets it off. thats probley where the leak is at

[tommy]

Do you see dye coming out of the drip tube?

[A.J.]

Your going to have a hard time getting 100% certainty that your evaporator is leaking unless you or someone you know has x-ray vision. I had an a/c leak in my van that I couldn't find. One day I was poking around with my black light looking for dye that had leaked out and noticed my crossmember was green with dye. I was then 100% certain that my evaporator was leaking. The condensation was running off of the evaporator, taking the dye with it, and dripping on my crossmember. That was the only way I would have known it was leaking. It took me two years to find it. Now you could use a refrigerant sniffer at the air ducts in the dash to see if it picks up a leak, but if it's a small leak you might not have a definitive answer.

A.J.

[Big_P]

I've never had luck with the A/C sniffer. Ours would go off if I blow on it, etc.

If we can't find a leak we just have the customer drive the car around for a few days with a dye in the system. Sometimes it takes a while for the dye to circulate through and (if it is a problem with the evaporator), to seep all the way down and through the drain tube.

[JDAWG]

the sniffers are not that great around cars, too many fumes/gases, anything will set it off, stick it up near your butthole and it will go off (try it)

[dixiedodge7369]

Ac dye is pretty good and showing up even in the smaller leaks if you don't trust them pepboys autozone all them sell kits to install your own freon and dye buy a kit and buy the freon with dye in it then get a uv light drive it around for a week or two then look with the uv light if you don't see anything then it's prolly the evaporator. ThEu will usually have tiny pin holes so the usually won't be pouring out of the drain tube sometimes not always.

[1966 dart wagon]

At our shop the mechanic uses nitrogen to pressureize the system then walks around it with soup and water solution and sprays it on the entire system, that is how he finds leaks, then when its fixed he has the tank set overnight at a set psi, last time it was 95psi and over night it didnt drop, indicating its good

[Vigo]

Ive actually pressurized a system through my gauges with a blow gun up to 100 psi and then just closed the valves and see if it held. A vacuum is nice but 29"hg is only 14psi difference at max. 100 psi vs ambient is 6x the pressure differential.

[RoadWarrior222]

That and you're trying to find stuff getting out, not in, and a seal leak might valve different.

[karlak]

Last time I had an evaporator leak the dye showed up at the vents.

[Vigo]

Last time i had an evaporator leak i had green fog pouring out the vents and got a major migraine.

That was what i'd call a 'catastrophic' evaporator leak.

[135sohc]

Evap core in mine cracked about 12 years ago, something you wont forget if it lets loose while your in the car.

[shackwrrr]

Ive actually pressurized a system through my gauges with a blow gun up to 100 psi and then just closed the valves and see if it held. A vacuum is nice but 29"hg is only 14psi difference at max. 100 psi vs ambient is 6x the pressure differential.

You know you can make refrigerant explode doing that right?

[RoadWarrior222]

Yeah but it only turns into phosgene, no biggie.

[Vigo]

You know you can make refrigerant explode doing that right?

Wait a second are you trying to tell me that pressurizing r134a above 100psi will make it explode?! I better not EVER turn on my ac compressor then... ... .. I didnt fire a blow-torch into my a/c line you know.

[shackwrrr]

a mix of oxygen and refrigerant under pressure can explode. Mainly r12

[BIGBRUDDA]

run the a/c on medium fan with the vents closed for bout 10 min. Then test at the center vent only, with a sniffer. This gives the gas a chance to build up in the fan box. Then you can spend all wknd takin the dash apart to look for the dye spot.
A 'wet sock smell" usually indicates a leaky evap too.

---------- Post added 04-19-2011 at 12:04 AM ---------- Previous post was 04-18-2011 at 11:59 PM ----------

Ive actually pressurized a system through my gauges with a blow gun up to 100 psi and then just closed the valves and see if it held. A vacuum is nice but 29"hg is only 14psi difference at max. 100 psi vs ambient is 6x the pressure differential.

The greatest problem is contaminating the system with oxygen.now ya need to flush with nitrogen.And 100psi is only bout 30% of design pressure ya know.

[Big_P]

Exactly. High pressure side can regularly see 150+psi.

With the low speed radiator fan not working on my PT (its supposed to come on when AC is engaged), A/C pressure on the high side got to past 350psi (pegged the gauge), and the high pressure relief valve let go. I don't think shop air is gonna hurt the system

[Badger]

what happened in my first post happened about 6-7 months ago. After he told me there could be a leak but he wasnt sure because he couldnt see any dye so I put out another $150 hoping this time the R12 would last. Between then and now I really havnt had a chance to drive the car much at all......maybe seven to fourteen days total in those 6 months. I go to get in it the other day and only hot air is coming out. I guess the R12 leaks out when the car is just sitting? I dont understand how that can happen but whatever. Gotta get this thing fixed one way or another. For the hell of it, I called Napa. They want $188 for the evap. Rock auto wants considerably less but Four Seasons makes theirs and i dont know if they are decent quality Evaps or not.