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

CAMRY99

MEMBER
1999 TOYOTA CAMRY
154,500 MILES

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.

Monday, September 26th, 2011 AT 12:22 PM

3 Replies

DRCRANKNWRENCH

MECHANIC
3,380 POSTS

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.

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Tuesday, March 16th, 2021 AT 6:40 PM

SAHILWALIA

MEMBER
11 POSTS

Since power for a/c is driven direct from engine crankshaft. It becomes stable as soon as the temperature reduces.

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Tuesday, March 16th, 2021 AT 6:40 PM

KHLOW2008

MECHANIC
41,814 POSTS

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

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Tuesday, March 16th, 2021 AT 6:40 PM