Posted: 7/16/2008 9:06:51 AM EDT
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Had my AC inspected four weeks ago because it was blowing hot air. They ran dye through and couldn't find a leak. They refilled it with refrigerant and said it may be a really slow leak. Went on vacation last week and when I started up the car after sitting for a week it's blowing hot air again. I can hear the compressor running so I'm guessing it's low again. To me that seems like a fairly significant leak. I had this same problem last summer too but I made it all the way to winter and the AC ran fine. Both the shop last year and this year couldn't find a leak. Any suggestions? |
I can hear it cycling on and off. I don't know if the system is still charged or not. I didn't want to pay someone to refill it if it's just going to leak out again unless a leak can be found and repaired. |
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I've got one of those refill kits from the part store that includes the gauge. I put it on the low pressure valve and get 25-45 psi that fluctuates as the compressor comes on and off. The instructions say that is the "filled" range. With the car off the pressure is 65psi. The compressor seems to be cycling every 30-45 seconds. Does that info give anyone some insight? |
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Seems like you have a sufficient charge, but taking a high side reading as well would give me a better idea of system health/performance from a compressor standpoint at least.. Is it getting cold under the hood? Based on what you posted I would look for a problem inside, specifically with a blend door actuator -or motor- depending on your vehicle. |
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I don't have a way to measure the high pressure side. The blend door actuator is working (it's new last year). Driving home today it was cooler outside than yesterday so I moved it to heat and the incoming air turned hot. Unless there is another door specifically for the AC system somewhere? What under the hood should be cold? It's a 99 Ford Taurus if that helps. |
The amount it too low. The pressure srops to 25 an it kicks out. When it goes up to 45 it turns back on. Add some until it gets to 40 while running, a little at a time. |
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I added one of the small cans that you can get from Walmart. I added it slowly and towards the end of the can it started to stabilize. It would sit at 25psi for a few minutes and then go up to 40 then stabilize at 25 again. The air is cool but not cold. I'm guessing I still need a bit more. I'll buy another can and see what happens. Any ideas on finding the leak? I've had two different mechanics put UV dye in there in the last 14 months and neither found a leak. |
Ask the technician to check the following, as both these leaks usually don't reveal any dye: The best scenario first - your service ports where they fill the system. The schrader valves (like a tire valve) can leak, and a tech in a hurry will disconnect the hoses after a recharge and not check them with a halogen tester. It will pass the vacuum and "sniff" tests because the hoses were attached at the time of testing. The second area, and vastly more costly to fix, is the evaporator core in the dash. It's located in the blend air / heater box next to your heater core. The best way to test this is, with a fully recharged system, place the "sniff" tester wand into the duct work on the passenger side of the car, preferably in the vents for the floor. Let the car sit turned off for a few minutes, turn the fan speed to LOW, and turn you ignition to the ON position to start the blower motor turning. If your evaporator core is leaking you'll get a detection. |
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A. Leak B. Too much dye in the system C. bad compressor D. under or over-charged 4 likely scenarios. It may or may not be the case, (I also have no idea what make/year/model your car is) but just because they looked under your hood and checked your A/C lines and such for leaks doesn't mean they looked under your dash at your evaporator. |
Not to offend but sniffers are useless. The only things you should use checking ac is something to test pressure, UV light, and common sense. Evaporators will leak dye, you just need to remove some covers to see if its actually leaking. Line valves do leak BUT they will be covered in dye AFTER a recharge anyways because that's where the refrigerant and dye is injected into the ac system. THIS DOES NOT INDICATE THAT THE SHRADER(sp?) VALVES ARE LEAKING! A tech in a hurry wont clean them out. You mentioned you took it to one or more shops to look for leaking dye, did you have your car detailed or clean the engine bay after having a recharge? P.S. - dye will always and eventually escape through a leak, even if you dont find it at first. |
No offense taken, but not using a halogen tester (and knowing how to properly use one) IMO is a disservice to the customer. Some vehicles may take over an hour of dash disassembly or more just to visualize a leaking evaporator. It's not necessary to "sniff test" schrader valves - it's easier just to apply a drop of PAG oil and see if it bubbles. |