Engine Size: 4.4l
Refrigerant Type: R134
Ambient Temp: 80
Country of Origin: United States
Bought car in fall 2010. A/C worked great fall, spring and early summer until July (2011) when the R134 had all leaked out. Mechanics recharged, but it was gone again in about 3 weeks. Charged again (plus tracer dye); gone in about 2 weeks. Subsequent charges and more UV dye (no time for repairs) lasted less than 2 days on a trip. Charged daily to get through the desert.
Mechanics and I have both done extensive UV and sniffer testing and found nothing anywhere. Mechanics deduce it must be the evaporator since they can't find the dye or a leak with the sniffer. Replacing the evaporator is a $2.5K, dash-out job. Yikes.
1) How can we verify that it's the evaporator before proceding with meatball surgery?
2) Could it be anywhere else where the sniffer and the UV couldn't find it?
Thanks for your help. This is a great forum.
Two things you need to do to check for evaporator leaks:
1). Check the evaporator drain area or tube for traces of dye. If it glows, I don't envy your having to pull the evap.
2). Keep the A/C blower on the lowest possible setting, and let the vehicle sit overnight. Insert the leak detector probe into a vent closet to the evap. Then turn the ignition key on first thing in the morning with the blower at the lowest possible setting. If the leak detector starts squealing like a stuck pig, have fun pulling the evap.
Finally, before pulling the evap, pressurize it with about 75 PSI of nitrogen and let it sit overnight. If it leaks down, assuming the test connections are tight, that's the source of the leak.
Pulling an evap is not fun, but it can be a DIY job if you have the time, patience, and a shop manual. It's all labor. I'd rather rent a car for a week or two, and pull the evap myself over a couple of weekends, than fork over $2,500. Either way, you need to confirm if it's the source of the leak before evap surgery.
Also, check the compressor shaft seal. Even it's not showing any oil or traces of dye, put a shower cap or plastic bag over it tightly and let it sit overnight, and then poke the sniffer in it.
Thanks Joe. I've gone under the car and can'tfind the evaporator condensate drain(s), but I'll have another go. Using the A/C in Colorado, NM, & Arizona means that we've get very little condensate drip out to carry out the dye. Your next test I can run myself. Sounds sensible since the R134 is dense and should collect in the evaporator overnight with the system pressure equalized.
I'll work with my mechanics on the N2 pressurization if we need to go that far. They're honest and experienced and we have a 25 year working relationship. BMWs are their specialty, but A/C isn't, though. I'll pay the $2500 but want to be darned sure we're nailing the root cause.
Thanks again for all the tips. I'm 99% sure it's the evaporator now (darn it!)
1) Got the car high enough to get under and find the condensate drains. Used the UV light and neither had any trace of dye, but they also looked as dry as a desert wash since we drive in areas of very low humidity.
2) Pulled the bottom engine cover and the compressor was bone dry with no trace of dye.
3) Don't have a full charge in the A/C; probably about half-charged. Figured I'd try the test as is and recharge if I didn't get any sniffer alerts with the TIF ZX-1 I got on eBay.
4) Ran the A/C set to coldest temp, lowest blower, and all vents closed except one for about 5 minutes. Got occasional very pronounced alerts at the open vent for 5-10 seconds, then the sniffer would settle down for a while, then another alert, etc.
5) Shut it down overnight. With the TIF sniffing at the A/C vent, started the car. It went nuts and alerted at maximum for about 20 seconds as the residual R134 vapor was flushed out the vent; then it calmed down with occasional alerts as before.
So I'm convinced it's the evaporator and it's time to pay the piper. C'est la vie!
Beats expensive shotgunning.
Ft. Collins, CO.
I think you've nailed it, but, I have seen cases where the outgassing of interior plastics sets off leak detectors, so my final suggestion is make some humidity before you pull the dash, either by running a humidifier in the vehicle for an extended period of time on recirculate, then check the condensate for dye, or mist the evaporator with warm water... pull the blower motor, pull a resistor pack, open a recirc door... whatever you have to do to get just a little access to it.
If you can see the evaporator coil (try mirrors or a scope if you have), and it is black and gooey or visible dye, then you have both electronic and physical confirmation the evap is leaking. Final pressurization test will confirm.
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