Heater troubles! Happy Flippin' New Year

[78GMCJIMMY]

The heater in my 78 GMC jimmy is givin' me TROUBLE! When it is cold and I turn on the blower motor it squeels like an SOB. It will stop after a few minutes but it is annoying! Could the squirrel cage need to be greased? Tonite it really freaked out on me and now the blower is stuck on high and stays on with the ignition OFF? I disconnected the battery for the night and am going to work on it tomorrow.Is it the switch,the resistor, or the blower motor? Or could it be all three?Any help is greatly appreciated! Oh yeah it has A/C but the pump is removed.​

 

[dirtwarrior17]

i don't know about 78's but i had a heater core go out on my 88' bout all the heating system expierience i got. not sure why it stays on.... might be bad wires or arking. Check the motor wires. If its not that you will probly have to find the actual on/off switch for the heater and see if it is stuck open.

 

[rerun93]

well if its runnin while the vechile is off i would say its the switch. or before the switch

 

[78GMCJIMMY]

Heater trouble

Well I finally got the blower motor to turn off by attempting to unplug the capacitor on the a/c box at which time the capacitor came out of the metal case and the blower turned off. I also tried to shut it off by simply removing the heater/ A/C fuse but removing the fuse did nothing? Any help is greatly appreciated.

 

[HarryH3]

EVERY GM vehicle that I've owned in the last 30 years would do the cold weather tweety bird impersonation. From 1970 Nova's to the 1994 Suburban. Even with new, aftermarket fan motors. There are no bearings in the motor, just bronze bushings. When they get cold, I guess they tighten up just enough to make that freakin' annoying sound.

As for the "stuck on high" problem, the contacts in the blower motor relay have welded themselves closed. For the high setting the contacts flip over to connect the blower motor directly to the battery. Since I'm pretty sure that there isn't a large capacitor in the circuit, then it's likely that the part that broke in your hand was the relay. It mounts on the a/c box and has a connector with 4 or 5 wires that plug into it. A new one should cost ya less than $15 at the parts store. If you want to try a new blower motor to see if the cold-morning squeal is solved (at least for a while) they cost $30 or less.

 

[diesel4me]

I oil my squeaky heater motors!

I too have experienced the "screaming demon" GM heater blower motors for most of my adult life!--when it gets to 15 degrees or so,the heater blower motors oftem emit a bizzare scream,sort of like the primal scream they play on "monster garage" when something goes awry..I got tired of hearing it on many of my cars and trucks,I replaced the motors on a few,but the new ones screamed louder than the old ones did(tighter bushings I guess)--the old motors would also make a "clunking" noise,that often made you think your motor was knocking,or other impending disaster was about to strike!.....

I drill a small hole in the cap over the rear bushing in the fan motor,and squirt in a small dose of motor oil about once a year,with the motor running,I do this in the fall usually--dont over do it or you will soak the brushes in the motor and it will fail..a little grease smeared over the hole keeps dirt and dust out,or you can use a dab of RTV to seal it up until next year....I've had the same squeaky,knocking fan motor in my 74 K20 since I got it in 1990'after one treatment with some motor oil,I havent heard any noises yet,barring a few days of extremely cold (-20F) weather that I dont blame it for making noises--I was making a screaming sound myself those few days!.....

 

[78GMCJIMMY]

Heater/relay problem solved!!

Well I pulled the jimmy into the garage after going to 2 local u-pull its and autozone for parts,and the total tally?Lifetime warranty blower motor from autozone $18.99,junkyard relay $2.50,junkyard blower dash switch $2.50= $23.99. Not bad huh. So anyhow I put on the junkyard relay and that actually solved the whole problem.However I decided it was worth $18.99 for a lifetime warranty and a chance at gettin' rid of the screamin' demon screech in the morning.So far so good,it's nice and quiet and I have a spare heater switch to boot.We'll see how it does this weekend up on Mount hood in 20 degree weather.Thanks for all the input once again I saved myself a Large bill from the shop. tomorrow it's a front wheel bearing repack!