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what are the weak links in an auto AC system?
If an AC compressor ran continuously (e.g., no evaporator temp sensor to prevent icing) then the system lost pressure, what are the likely leak points?
Thanks, Sixto 87 300D |
#2
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O-rings? Have you tried to pressurize the system WITH some AC dye and scan with a blacklight?
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01 Ford Excursion Powerstroke 99 E300 Turbodiesel 91 Vette with 383 motor 05 Polaris Sportsman 800 EFI 06 Polaris Sportsman 500 EFI 03 SeaDoo GTX SC Red 03 SeaDoo GTX SC Yellow 04 Tailgator 21 ft Toy Hauler 11 Harley Davidson 883 SuperLow |
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if it did that than it has blown out the reed type valves in the high pressure side or maybe both and the compressor has gone away - jz
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#4
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The weakest link in most automotive AC systems is the evaporator- the heat exchanger that cools the inside air.
It is the weak link for many reasons 1) Its a heat exchanger - lots of connections and pipe joints, thermal stresses. 2) Its crammed into a small space, near the always-hot heater core 3) if it gets dirty, it will get clogged and freeze up, the ice formation inhibits cooling and further temperature-stresses the metal 4) its in the most difficult/expensive place to find and replace =) 5) Its also in the toughest place to diagnose (in order to see dye leaking out, you have to look into the vents or the drain line.... In my limited shadtree mechanic experience, 7 times out of 10, if there is an AC leak, its from the evaporator. Inject UV dye and look down the vents (each one) around the drain line, run the system a lot to disperse the dye. I've also seen leaks around the compressor shaft - the UV dye will show up between the A/C clutch pulley and the compressor housing. you need to get that dye in the system if you want to know for sure -John
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2009 Kia Sedona 2009 Honda Odyssey EX-L 12006 Jetta Pumpe Duse (insert Mercedes here) Husband, Father, sometimes friend =) |
#5
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I am pretty sure the AC compressor on my 19 year old 560 SEC simply has, just totally, seized up.
It threw its belt, so that when it let go, it whipped around the one for the alternator and tore that one to pieces, too. Replaced both belts and it did the same thing again 2 days later. So... The car is now running on the alternator belt only, and the HVAC one is off, for the winter, don't need AC for this snowy weather, and you can now see where the now bare AC pulley has rubber all over it from where the belt could not move and fused itself to the pulley. I will be waiting to warmer weather to buy a new HVAC conpressor and another belt to try and take care of it.
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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ... 1995 E 420, 170k "The Red Plum" (sold) 2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp 1967 Mercury Cougar, 49k 2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold) |
#6
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A refrigerant sniffer works best for indentifying a leaking evaporator. Any shop doing A/C work will have one.
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Sorry to hear about that, Jim!
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Current cars: 2000 ML55 AMG, 174k miles 2003 C240 T-Modell, 202k miles 1995 S320, 207k Miles |
#8
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Got to be careful though. Some of those sniffers are tricky. A good trick they do is make sure the sensor accidentally hits something and it will go off so they can say "See!! There is one leak"
__________________
01 Ford Excursion Powerstroke 99 E300 Turbodiesel 91 Vette with 383 motor 05 Polaris Sportsman 800 EFI 06 Polaris Sportsman 500 EFI 03 SeaDoo GTX SC Red 03 SeaDoo GTX SC Yellow 04 Tailgator 21 ft Toy Hauler 11 Harley Davidson 883 SuperLow |
#9
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There's no other way to identify a leaking evaporator in many cars. I used one to pin down a leak in my E320. Being carefull is part of everyday life.
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#10
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I use a sniffer in conjunction with UV dye. I just replaced the evaporator in my Miata this past week due to a pinhole leak. Sniffer picked something up, but UV dye confirmed it. After replacing the evap, I found a leak (using UV) at the high-side o-ring on the compressor. It evidently blew out when the TXV stuck closed (long story). Anyway, after replacing TXV, drier, evap, and some O-rings, I finally have A/C back in the car. I'm glad I chose the winter to work on it!
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08 W251 R350 97 W210 E320 91 W124 300E 86 W126 560SEL 85 W126 380SE Silver 85 W126 380SE Cranberry 79 W123 250 78 W123 280E 75 W114 280 |
#11
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You can typicaly find a sniffer at a pawn shop. Take a can of R-134 along with a tapping hose so you can release a bit of 134 and test it. I have found tiny leaks with mind, so I no longer use the dye. But then, it is a personal preference depending on which one works the best for you.
If you compressor seems locked-up it just might be the compressor clutch. BEWARE--- If your compressor clutch is frozen up then just replacing it will likely cure the trouble for only a few weeks. When the clutch is worn out the compressor is just about shot as well. |
#12
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The compressor engages and doesn't make untoward sounds when the low pressure switch is bridged.
Can a shop find leaks in an R12 system without filling with R12? It's not a slow or gradual leak. The system worked one day, didn't work the next. Zero pressure on the high and low sides with the compressor disengaged. Sixto 87 300D |
#13
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Quote:
they can fill it find the leak and unfill it charging you for the lost R 12 its the way we did it - jz |
#14
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No need to waste precious R12. Just put a $8 can of R134A with UV dye into the system yourself. Turn the A/C on for about 1 minute to circulate, then shut it off and go searching with your black light. The R134A eventually evaporates out of the system, and there's no harm done.
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08 W251 R350 97 W210 E320 91 W124 300E 86 W126 560SEL 85 W126 380SE Silver 85 W126 380SE Cranberry 79 W123 250 78 W123 280E 75 W114 280 |
#15
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Quote:
__________________
01 Ford Excursion Powerstroke 99 E300 Turbodiesel 91 Vette with 383 motor 05 Polaris Sportsman 800 EFI 06 Polaris Sportsman 500 EFI 03 SeaDoo GTX SC Red 03 SeaDoo GTX SC Yellow 04 Tailgator 21 ft Toy Hauler 11 Harley Davidson 883 SuperLow |
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