I know there are TONS of posts on heater motors, and vents and everything else, but I haven't really seen one that matches what I'm experiencing. Close, but not the same.

The problem is that the fan doesn't work consistently. I can turn it on and off just fine. After school today, I got int h car and left school forgetting the fan was on(didn't hear it or anything) and I stopped for gas. AS I pulled out of the station, and hit the gas the fan came on. It acts almsot as if it's connected to the throttle(obviously it isn't). Could it be a sign of the motor going bad? I thought the motor was fine because it goes through the different speeds, and works as I assume it should. I also don't get very much air through the vents even on high.

Thanks guys!

 

Are you sure it's not working always, but maybe just only blowing out the defrost vents sometimes (indicating a vacuum leak)?

 

I can hear it come on and off. I can feel it too, it's a big burst of air when it does randomly come on, then it's back to almost nothing.

 

Is it at just the high speed setting, or all of them? If just high speed, I'd check the relay and wiring for it that is attached right to the heater box. If it's only low speed settings, then I'd try replacing the resistor in the heater box housing.

 

I have the fan on high all the time since there is little air coming out, Where is the relay for the heater fan?

 

 

How do I check the relay? I just took the heater fan out and everything to check inside for any leaves and stuff and realized the fan was sealed in with some type of caulking and only one screw. That might be why I get no air flow.

 

You should hear or feel it 'click' when someone turns the fan on. Remember, the fan stays on always unless the lever is slid to OFF. You can unplug it, check the wiring connector for burns and such.

If it has markings on it (sometimes on the top), then terminal 86 should be a ground, terminal 85 should get 12v+ when the fan is turned on (high setting), terminal 30 should have 12v+ always (with key on), and terminal 87 should have 12v+ only when fan is on (high). I believe, if there is a terminal 87a, it should get 12v+ only when fan is on lower speeds (there's 3 speeds, low, med, hi - terminal 87 should only have 12v+ when set to hi, terminal 87a would have 12v+ when set to lo or med).

 

 

I haven't checked the relay yet, but isn't it good because the motor does come on?

 

It's a SPDT relay. I'm not 100% sure, but I'm assuming that the relay switches power between one relay terminal and the other, so that when blower is on high, power sent directly to the blower motor, when on low or med, power sent to the resistor then to the blower motor (where the resistor lowers the voltage along the way).

So, if looking at relay diagram, for example when set on high, power runs from 30 to 87 (straight to motor), when set on med or low, power sent from 30 to 87a (which routes through resistor). Since 87a is the default (relay not activated or not working), lower speeds would still work.

 

What I'm not understanding is why I can still go through all the fan speeds. If the relay was bad, wouldn't it not work on all speeds? Or, is is possible that the relay works sometimes and not others?

 

I would just buy a new fan motor from your local chevy dealer. They are not that expensive ( if I remember right around 30 bucks) and it is common for them to go bad.

 

The relay might be fine - it was just that it's an easy part to test and a cheap part to replace (under $10). But yes they can work sometimes and not others.