91Firebird305

Ok, here is the deal. I have read just about every post I can on blower problems, but I can’t seem to find a solution to my problem. My car is a 1991 Pontiac Firebird with a 305 V8 TBI, Automatic.

I recently repaired and retrofitted my A/C over to 134a, but the problem that I am going to describe was happening prior to the a/c repair. Here we go….
When I turn on the air, (either A/C, Heat, or just Vent), sometimes it will blow out just great from all settings. Other times when I shut it off (the car or just the air) and then turn it back on, or even when it has been running for a while, it will barely even trickle the air out at any setting (low thru high). And sometimes if I am lucky, I will just leave it turned on, even though it is just trickling the air out, it will kick back on at full pressure on it’s own after a while. Other times, when it is blowing out fine, the pressure will drop...not to a trickle, but not as fast as it should.

Will a blower motor do this, or is it a relay? Can the blower motor work intermittently and at different levels or do they just go out??? I am really confused.

Thanks in advance for any help,
Rob

Zap Racing

Sounds like a vacumn problem--similar to the problem I had recently. There is a vacumn switch connected to the slide switch in the dash that controls all the functions. If it develops a leak (can't necessarly hear it leaking), it will not send the vacumn to the different trap doors that control the air flow. There are also other areas in the system where a vacumn leak could be causing the problem, but I would check the switch first. If that's not it, start looking around for worn or dry rotted vacumn hoses or maybe just one that got disconnected either under the dash or around the firewall on the passenger side. Maybe some more knowledgable people in this area could help with other comments!

91Firebird305

Will a vacuum problem be intermittent? And with a vacuum problem, won't there still be air coming out from somewhere if the unit is just "stuck" somewhere because the vacuum switches aren't working??

Zap Racing

Yes, a vacumn leak could be intermittent. As it builds up vacumn it will make the system start working and all the trap doors open or close. Check and see if the blower motor is running, and responds to the different speed levels--even if air is not coming out of the vents. If it is, I'd keep looking for a vacumn problem or a control switch problem. If fan does not respond, it might be the speed control resistors that control fan motor that are mounted on the plastic box whereblower motor is. (under hood on pasesenger side by firewall.) Would be several wires that U could see on top side visible of small flat piece with a couple screws holding it in place. The resisters are underneath where U can't see them.

I hope someone that knows more about this subject would also post some info here!

Good Luck

91Firebird305

Well, I decided to test the blower motor before spending the time looking for a vacuum leak. I tested for voltage to the motor and it was hot, but the motor wasn't turning....so bad motor.

I replaced it and everything seems fine.

Zap Racing

COOL!!! (No pun intended--well maybe a little!)