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A/c Not Cold After Ten Minutes


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Hi -

I have a 98 SC300. The A/C is nice and cold every time I start up the car when the car is cold, but then like clockwork, after about ten minutes, it's just as though I turned the A/C off, and will remain so until I park the car for a while . If I turn off my car and then on again this doesn't make it cold again, apparently the car has to sit until it gets cold again.

Not only is it frustrating because of the heat, but it also won't defrost.

Any ideas what could cause something like this?

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Hi -

I have a 98 SC300. The A/C is nice and cold every time I start up the car when the car is cold, but then like clockwork, after about ten minutes, it's just as though I turned the A/C off, and will remain so until I park the car for a while . If I turn off my car and then on again this doesn't make it cold again, apparently the car has to sit until it gets cold again.

Not only is it frustrating because of the heat, but it also won't defrost.

Any ideas what could cause something like this?

Sounds like a bad heater valve. It controls flow of engine heated coolant to the the HVAC fan box. If it does not shut off the hot water flow, your AC will not be able to cool the car. You may also be low on freon, and have reduced AC efficiency as a result.I saw an article about how to replace heater valve on the net, maybe planet soarer. Good luck.

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Well it's definitely not low on freon, the a/c was completely redone just before I bought the car, the seller gave me the receipt. (Unfortunately that repair shop is far away from me and never answers their phone or returns my calls.) <_<

It really acts as though I turned off the a/c - not only does it suddenly go from freezing cold to tepid after 10 minutes, it gets really humid in the car as it would with the a/c off too.

So is the heater valve the only thing it could be?

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Well it's definitely not low on freon, the a/c was completely redone just before I bought the car, the seller gave me the receipt. (Unfortunately that repair shop is far away from me and never answers their phone or returns my calls.) <_<

It really acts as though I turned off the a/c - not only does it suddenly go from freezing cold to tepid after 10 minutes, it gets really humid in the car as it would with the a/c off too.

So is the heater valve the only thing it could be?

There is a diagnostic code system for your AC system. I don't remember how to access it but use the search function. It's fairly simple like press and hold two buttons and look at the display of the temp. I'll see if I can find it and post it for you.

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Sounds to me that the evaporator is freezing over, it turns into a block of ice. All it needs is to be charged a little bit more. Get it checked out by a A/C mechanic it shouldn't be much.

Good idea. It should take longer to freeze up at higher fan speeds, so you could try to test that theory.

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Sounds to me that the evaporator is freezing over, it turns into a block of ice. All it needs is to be charged a little bit more. Get it checked out by a A/C mechanic it shouldn't be much.

Good idea. It should take longer to freeze up at higher fan speeds, so you could try to test that theory.

Thanks!

Here's a new thing I discovered last night: if I leave the A/C off while I'm driving for a long period of time then suddenly turn on the A/C, it is cold. So it has nothing to do with the car being warm.

Any other possibilities? Given the symptoms I've mentioned could it still be the heater valve as the original replier suggested?

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Sounds to me that the evaporator is freezing over, it turns into a block of ice. All it needs is to be charged a little bit more. Get it checked out by a A/C mechanic it shouldn't be much.

Good idea. It should take longer to freeze up at higher fan speeds, so you could try to test that theory.

Thanks!

Here's a new thing I discovered last night: if I leave the A/C off while I'm driving for a long period of time then suddenly turn on the A/C, it is cold. So it has nothing to do with the car being warm.

Any other possibilities? Given the symptoms I've mentioned could it still be the heater valve as the original replier suggested?

Sounds less like heater valve from that. Could well be a bad freeze switch or low on freon. Try keeping the fan speed to max and see if it blows cold any longer.

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Does your compressor cycle on and off??

I agree that it sounds like you are a little low on freon and the compressor is not cycling.

If it does not cycle, the moisture in the air will eventually clog the evaporator and cause your issue just as the others said.

Start your car, turn the AC down to COLD, keep the RPM at about 1500 and check the AC sight glass. It is in the AC line that runs very near the driver side headlight.

You should not see bubbles. If you see bubbles, then you are low on freon.

If you are low on freon, you may have a slow leak.

Tom

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