Hello, I'm trying to help my aunt with a weird ac problem. She has a 97 blazer v6 with the manual ac controls.

The issue is that the vents will change in all modes, forward, floor, defrost, etc
But if she puts it on a/c or max ac, the fan slows down and seems to kind of blow out of all the vents very poorly.

It doesn't change to blow at for face for the front vents, and it seems (not sure) that the fan just gets really slow.

I have read some other posts but couldn't find a problem like this.

Maybe one solution is one of the actuators isn't working? Which actuator would control this and where is it? If we could just switch it manually and never have her change it that would be fine as well. We live in FL so we use ac 99 percent of the time. I'm also going to check for blockages in the evap coil.

I also read this could be the relay, do you think that might be the case here? Would there be a way to test it?

Thanks for any info you can provide.

 

Does the speed slow down on every fan speed setting? Do you have and know how to use a digital multimeter?

George

 

​​​​​​So on the regular settings (non-ac) the fan does properly work at all settings, it goes from low-med-hi.

on the ac setting i can't really tell because it is weakly blowing through all the vents, but I can tell it definitely slows down on the lowest setting,

Yes I have a multimeter and can use it. I've worked on lots of different cars and Ive rebuilt a few as well, just never had a problem like this. Thanks!

 

There are two different circuits that run power to the fan motor. The highest speed and then everything else. The lower speeds are what use the resistor network. But before we get too carried away on the motor electrical testing, you should get the vents straightened out because that can change your perception of fan speed. Member Christine_208 is the resident expert on the HVAC controls. If she does not chime in, send her a message. If fan speed problems persist after that we can go further.


George