Blower motor will not shut off completely
 

Whenever I slide the top switch to the "off" position, and the bottom switch to "cold", the truck still cranks out hot air through the floor vent right by the shifter, and makes it unbearable to drive on warmer days. I do need a new temp. control assembly because my fan switch will not mount since the screw mounts are broken. Thus my fan speed is always on low (all the way down).

Will a new assembly allow it to stop blowing hot air all the time? The last time I had it apart I lubricated the crap out of the control wires, and still will not stop blowing hot air. If this doesnt work, am I looking at more repairs so the blower will completely shut off when I want it to?

Re: Blower motor will not shut off completely
 

The blower motor is on any time the ignition is on, to provide ventilation in the cab. It's never really "off". I've known a few people that didn't like this aspect, so they just cut the low-speed wire.

The temperature control, however, is another story. It shouldn't be hot air all the time, time to check the cables, blend doors, and vacuum lines.

Re: Blower motor will not shut off completely
 

Most people install a simple on off switch to fix this issue. Cut wire, install switch in line. Done deal.

Re: Blower motor will not shut off completely
 

I unplug mine. Though I only drive my 74 in the summer

Re: Blower motor will not shut off completely
 

Two things that applied in my situation. I have a 73 Jimmy so its similar.

First, I got a 4 way blower switch from a later truck and left the low speed position unhooked so it now is "off."

Second, the rubber seal at the cowl that seals when the hood is down was missing. This let hot engine compartment air into the fresh air ducts which is where the blower gets its "cool" air from. I could not get it to blow cold until I replaced the seal. In fact, since I had a cowl hood too, I had to seal up the back edge of the hood itself to keep the air from coming through the vents. Now the hot air goes out of the hood where its supposed too and things are nice and cool in the truck.

You might check the condition of the rubber hood seal. Also, the temp control slider moves a little door so you should be able to see (and hear) that move as well.

Re: Blower motor will not shut off completely
 

I like that idea of a 4 way switch, so I will probably order one.

I do hear the temp control door when I move the switch, but if you could, could you point out where that seal exactly is? I just want to make sure I get the right part that I need.

Re: Blower motor will not shut off completely
 

It's the gasket seal on top of the cowl (black strip of rubber) in this pic:
https://lh4.googleusercontent.com/-0...902_175013.jpg

If its missing the hot air from the engine bay runs through the gap and into the cowl vent area and down to the blower fan intake. Once the engines is hot it can make things nice and toasty in the truck.

Re: Blower motor will not shut off completely
 

i've read it's called "power venting" to bring in fresh air
i cut the brown wire on the 78(three speed),and the 79 (4 speed)
so both have off

also the defrost/floor control has three holes for ajustment
giving1/3 up all the time
all up or down
or 1/3 down all the time
need to have the air box apart to ajust....

Re: Blower motor will not shut off completely
 

Early on people complained of exhaust fumes in the cab so gm "fixed" it by having the motor always on. Although In my 86 I can take the switch to "off" position and the fan shuts off. Otherwise it's always going
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Re: Blower motor will not shut off completely
 

Mine definatley does not have that, so that could be my problem. Where can I get one? LMC?

Re: Blower motor will not shut off completely
 

Yes, lmc. Might even be able to get one from the dealership. There are other sources too. Check the vendors on the site directory or Google it.
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Re: Blower motor will not shut off completely
 

I'm missing that also...No fumes coming in even with no heater box installed..LOL
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Re: Blower motor will not shut off completely
 

my 78 hood seal is off too since i painted it red.....lost it in the parts dept lol
I get some fumes,sometimes out of the turn signal hole lol
but thats blowby..or my undercoating....and it's cheaper then cigarettes!

Re: Blower motor will not shut off completely
 

I found it on LMC for 10.95, going to add that into my order so my air controls will work as good as new. Thanks for the help on that