Why does my A/C, heater blower fan speed fluctuate then cut out the longer it is used ?

1999 TOYOTA CAMRY
154,500 MILES
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CAMRY99
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In the beginning the blower fan only worked on high. So I replaced the resister with a new one I bought off the internet. It worked fine for a few weeks then the blower speed started to slowing down on its own the longer it was on. I figured I got a junk part off the internet. So I went to a dealership and bought the OEM resister and installed it. Again it worked fine for a couple weeks. Now the blower speed will go up and down on its own and then go slower and slower till it cuts out completely the longer it is on.
Sep 26, 2011 at 12:22 PM
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DRCRANKNWRENCH
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It could be the blower motor. You can test it by checking it with a multi-meter on the high setting. It should have 9-15V generally.
it sounds like the motor is failing. It is not automatic, so it does not go through computer, from the wiring diagram I have, so the only other thing is the control panel switch and they don't fail as often as the blower motors do.
Mar 16, 2021 at 6:40 PM
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SAHILWALIA
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Since power for a/c is driven direct from engine crankshaft.it becomes stable as soon as the temperature reduces.
Mar 16, 2021 at 6:40 PM
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KHLOW2008
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Yes, it sounds like a failing motor. When motor starts slowing down, give the the blower motor housing some banging with your hands and if the speed picks up, the motor is due for replacement. But you should still use a meter to verify good voltage. A bad motor can strain other electronic parts causing them to fail as well

See the guide below on how to use a meter


https://www.2carpros.com/articles/how-to-use-a-voltmeter
Mar 16, 2021 at 6:40 PM