88 burb blower motor keeps blowing fuse and poor air flow.

[Stopman33]

It's not a different motor on the later squares,squares got the motor before the GMT 400. So the difference is early and late squares. Also as you decrease voltage the amperage draw increases,so running a straight 12v to the motor won't be an indicator as to what amperage the motor draws after the resistor drops the voltage.You could check with a clamp on ammeter.

Ahh I see, so my truck would already have the later motor. Still learning these trucks lol. I can certainly check the amp draw. I’ll get back when I have some time to tinker more with it.

 

[Stopman33]

Metal clip came in and I installed it. it seems now like the door is getting stuck when trying to switch between defrost and vent, if I give the door a little push it seems to operate. When its on defrost I do have air flow out of my defrost vents finally!

I'm 99% certain the ground on the body for the blower motor is crap. Will fix that here shortly and test again, lotta snow coming would be nice to have heat again!

 

[Stopman33]

Ground on the body was indeed the issue. It looked okay but underneath it was a bad connection, cleaned that and actually put a smaller fuse in (20amp instead of a 25) and on my test drive it did not blow once. still confused on the door situation... also my air flow is still terrible, the only setting that works well is when the mode selector is set on HEAT, it blows pretty well out of the foot vents and is the best air flow I've had out of that system yet.

 

[jcperformance]

Sounds like you might have a couple issues going on. Weak airflow and no defrost could be a broken blend door or vacuum line, which is pretty common on these. If the fuse keeps blowing, the blower motor itself might be pulling too much current, so it could be worth checking or replacing that too.