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AC quits working when stopped
04-18-2014, 10:24 PM
Post: #1
AC quits working when stopped
My AC quits working when in stop and go traffic or at a long light. Comes back on when I get going again after a minute or 2. One shop says thermistor another says thermostat is faulty causing engine to overheat. Not sure who to believe. Car gauge never shows engine to be overheating. Can anyone help me? 2007 Hyundai Tiburon
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04-18-2014, 10:47 PM
Post: #2
RE: AC quits working when stopped
If it still blows but starts to get warm at traffic lights that could be a sign of the AC system being low on charge.... BUT.... there's more to it since the only way for it to be low is for there to be a leak. You could fill it up (if that's the case) and recharging could last a few weeks, months, or maybe even a few years. Hard to say without being there. OTOH, a good shop will look at it before jumping the gun on a quick opinion.

BTW, those other issues mentioned could be suspect as well, but without seeing the vehicle it's hard to say, although I would be hard pressed to believe a hot engine is the cause. You see, the AC condenser is in front of the radiator so as long as you are moving or the fan is running (out front) the AC doen't know the difference. This is where GOOD diagnosis and an honest shop is key!

Let us know how you make out.
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04-18-2014, 11:08 PM
Post: #3
RE: AC quits working when stopped
Both shops did the AC check. It was even listed on the report I got from the 2nd shop. They recharged prior to doing the AC check. I have a hard time believing my car is overheating when the temp gauge doesn't show it. But I am not convinced that it is the thermistor either. The joys of not knowing enough about cars! The possibility spending 400 - 600 dollars on the wrong diagnosis is going to keep me up at night...lol
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04-19-2014, 01:35 AM
Post: #4
RE: AC quits working when stopped
Has anyone actually checked to make sure that fan that Rupe mentioned is actually running? While moving down the road the air blowing through the condenser will cool the freon. But when moving slow or stopped at a light you need that fan to move air through the condenser. It’s pretty easy to check. Raise the hood on the car and locate the fans. (There’s usually 2.) Start the car with the A/C OFF and go look at the fans. If the engine is cool neither fan should be running & if it’s warm one fan should be running. If you turn the A/C ON the other fan should run.

Check that out. It could be as simple as a blown fuse, a bad relay, broken wire, or a bad fan motor?
Please let us know what you find.

Thanks for using the forum,
Garner

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04-19-2014, 10:50 AM
Post: #5
RE: AC quits working when stopped
So let's back up a bit here. You said two shops looked at it and one did a recharge BEFORE diagnosis? Maybe we don't have all the details but something doesn't add up unless the system was empty and they couldn't do a diagnosis without recharging. Perhaps they didn't charge it all the way or some has leaked out already. Either of those can do exactly what you say. Again, hard to say without seeing the compressor cycle and the gauge pressures.... then there's the time lag between when the original work was done versus now.
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04-19-2014, 12:48 PM
Post: #6
RE: AC quits working when stopped
From the quote they emailed me: A/C PERFORMANCE TESTING L2: This diagnostic testing will remove existing refrigerant and charge the system to the proper amount to test for leaks and for proper air vent temperature. In the event of poor performance, we will determine the failing component(s). When they called me they said the problem was with the thermostat overheating the engine. Again, from the quote: TECHNICIAN COMMENTS: THERMOSTAT AND GASKET DEFECTIVE AND OVER HEATING THE ENGINE. But I have never seen my temp gauge show the engine as too hot. Both shops performed an AC test, neither found an issue with the AC system. And I should also note, the air still blows it just gets warm. Then, after I pick up speed for a constant minute or 2 it will get ice cold again. It only gets warm when I am stopped for several minutes, like if I don't make it through a stop light the 1st time or I am in a traffic jam. Other than that the ac functions great. Someone told me my problem was I was taking it to Christian Bros & Firestone and not to a certified AC shop. That made me laugh, but he is probably right, I think that is what I will do and not let Christian Bros or Firestone work on it.
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04-19-2014, 01:28 PM
Post: #7
RE: AC quits working when stopped
There are some systems that will shut down the AC as the engine temp rises and perhaps you never sit at a light long enough. IOW, if those fans (out front) fail to come on then the AC suffers. After several more minutes the engine temp goes up but not enough for you to notice. With the info we have so far it would seem there's stil a piece of the puzzle missing, which may very likely be those fans are not operating when they should. There are also several temp sensors controling the systems so one of those may be sending the worng info to the computer.

As much as I hate to say it, sometimes a dealer is more familiar with the various quirks and even though their labor rate is usually posted higher (by the hour) there are times when diagnosis costs half as much simply because see these things more often.

Again, without personally seeing the comp cycle and the gauge pressures it's hard to pin this down. IOW, if the comp is running and the temp goes up then the pressures will tell a story. If the comp goes off then there's reason to look at why.
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