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Heater control help

chicken joe

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Apr 3, 2013
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Sheboygan, Wi
Good evening all. i have a 76 k5, it had air at one time, the controls are still for the a/c. My fan blows every where but high, not sure if that helps or not.

my problem is my selector lever is off one slot so when i go for defrost, it blows heater or what ever is one befor defrost. im prety sure this can be adjusted. i just dont know how or where to start.

thanks in advance
mike
 
There is a relay under your hood right beside your heater motor, it bypasses the heater resistor when you turn to high. If every speed works but high, your relay isn't switching over. Probably need to make sure the relay is getting the signal from your selector switch in your dash first. Your heater controls are adjustable, pull the glove box out and you'll be able to see all the cables, they adjust where the cable attaches to the heater box.
 
thank you, i brobably should have said i already replaced the relay under the hood and the resistor in the heater box. i can live with not having high fan but i need to adjust the cables to get it to switch to defrost.
 
The cable only controls hot/cold. The rest of it is vac controlled, pull the controls out of the dash and look at the selector in the back of the panel.

There is a single fuse on the firewall for the high blower, fuse comes off the junction block.
 
The cable only controls hot/cold. The rest of it is vac controlled, pull the controls out of the dash and look at the selector in the back of the panel.

There is a single fuse on the firewall for the high blower, fuse comes off the junction block.

What year did they switch to vac. instead of cable? I figured a 76 was still all cable. It's still adjustable on top of the heater box even with the vac. though.
 
My 74 k5 has the cable for hot/cold going to the top of the heater box that controls the blend door and every thing else is vac controlled.

I don't know about 1st gens but 2nd gens were this way at least to the 80's far as I know.
 
well i tore out the contorl panel i have cable hot/cold and vaccuum selector switch. im going to comtletely remove it and see if i can clean it up a little and see if i have a leak somewhere.

high fan and max a/c dont work is their a special relay or something for the high fan???

thanks again everyone
 
There is a single fuse on the firewall for the high blower, fuse comes off the junction block.[/quote]


where might this fuse be?
 
well this is what i just found out i have defrost at idle but at 3000 rpm i have nothing, no vents, no floor.

my blower problem is the red wire coming from the blower housing under the hood isnt connected to anything. when i connect it straight to the battery it works like it should. so i have to find a permenant place to mount it. any suggestions?
 
Check your vac reserve ball, cracked or not hooked up.

Otherwise you have a vac leak like you said.
 
thanks for the pics. on my rig that wire has been cut and spliced and just sitting under the hood not hooked up to anything, on problem solved.

so far from what i can find all vaccuum looks good. my dad told me last night i might need to find a different source of vaccuum, currently it goes to the bottom of the carb.
 

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