Heater worked great now no air flow.

[ruedger455]

HELP!!!! Heater worked great now no air flow.!!PICS up!!!

Hey guys. I just bought a 77' gmc k2500 and the heat was working great and blowing out strong. Then i turned the truck off and when i turned it back on there was nothing. No heat and no airflow coming through anywhere. Could my blower motor have gone out? Let me know what you guys think i should do.

 

[Driver4r]

Sounds like a strong Possibility, check and see if your power wire at your fan has power.

 

[chengny]

It's probably going to turn out to be the resistor stack. But here is how to test the blower motor. On the engine side of the firewall, in the upper RH corner (pass side), is where the motor is mounted. There should be only one wire that connects to the motor. It has a little rubber boot on the terminal. Pull that connection off and supply the spade terminal on the motor with 12VDC.

You can run a little jumper wire from the battery or use a battery charger (has to be an old style battery charger - not one of the new "smart" charges. Attach thye red clip to the blower motor and black clip to any convenient ground.

If the blower operates that way - it's good. Next step, remove the resistor stack from the plenum and inspect it for burnt coils.

 

[ruedger455]

Where is the resistor located?

 

[Milblazer]

Sounds like a strong Possibility, check and see if your power wire at your fan has power.

Might even just be dirty. I looked at mine a while ago and it was all full of crap. Might want to take a wire brush and clean up everything. A $1.00 brush is a lot cheaper than a new blower motor and with an old truck you'll definitely be using it again. Couldnt hurt to take it off and see if something is keeping the motor from spinning. I've heard a lot of stories about nests being made in there.

 

[ruedger455]

I just went and looked at it. There is a hose that comes off the side of it thats disconnected! Whats this hose?

 

[chengny]

This is from a later model but yours should be very similar.

You must have A/C - that hose is to supply the motor with cool air.

 

[ruedger455]

Can i get to the resistor without any disassembling? And would mine have an 11/16 or 7/8 vent hole? Its a 77 gmc grande sierra 2500.

 

[Milblazer]

Here are some more pics. The resistor is the diamond shaped thing. It can be taken out without disassembling everything.

 

[ruedger455]

This is awesome info thanks guys. But im going to replace both of them. But im not sure which blower motor to get. Theres one for 11/16 vent hole and 7/8. Ill try and take some pictures today.

 

[ruedger455]

Here are some pictures of my setup.

 

[ruedger455]

So since i dont have an a/c anymore i could get a new motor that is for a non a/c truck?

 

[chengny]

No the blower motor used on A/C applications is bigger so it pulls more amps. Plus you'd have to hack into your wiring harnes and splice on a new connector. I don't even think it would mount correctly on the plenum housing.

 

[ruedger455]

Ok thank you that saves me some trouble.

 

[Milblazer]

It wouldn't be that hard to swap out an AC harness for a heater only harness. You'd have to swap out your AC/heater control for a heater only version. Also, take a look at the pictures you posted, mainly the second one. I can see some bare wire where it looks like the radio noise filter connects to the purple wire that goes up to the relay. Might want to check that out for corrosion.