Only hot air out the vents

[sbwrench]

Hey Guys,
My Sy is only blowing hot air out the vents irregardeless of where I have the switches set. A/C comes on when you switch it to a/c but only heat out the vents. Same if you put it on vent with temp switch on cool at the bottom. It almost seems like heater valve is in-op but I can't seem to locate one. It appears that everything is vacume operated.

Can anybody steer me in the right direction? Thanks.

Al

 

[jjorgensen52]

Re: Only hot air out the vents

Is the temperature lever real easy to set? That is cable operated, there is a cable attached to the lever and runs to a flap in the ducting.

The best way to access the linkage to check for binding, etc, is to empty your glove box and pull out the access panel at the back (two self tapping phillips pan heads, they're something like a #8 x 1" IIRC). You can see the duct valve linkage right there, and see if it is stuck. If it isn't, most likely your heater control is broken and will need R&R'd. To do that you just drop the two screws out and pull it forward. If the cable is off, it will come out easily. If it's on, it will come out maybe 3/4" and then stop

 

[sbwrench]

Re: Only hot air out the vents

Great info, thanks. It feels like the temp control is vacume operated so if it's a cable I'm sure it's off on either end. I'll check it out. How do you like New London? Grew up right across the Thames. My dad was Sub Service.

 

[Sy-1177]

Re: Only hot air out the vents

Is the temperature lever real easy to set? That is cable operated, there is a cable attached to the lever and runs to a flap in the ducting.

The best way to access the linkage to check for binding, etc, is to empty your glove box and pull out the access panel at the back (two self tapping phillips pan heads, they're something like a #8 x 1" IIRC). You can see the duct valve linkage right there, and see if it is stuck. If it isn't, most likely your heater control is broken and will need R&R'd. To do that you just drop the two screws out and pull it forward. If the cable is off, it will come out easily. If it's on, it will come out maybe 3/4" and then stop

Good stuff! My truck is doing the exact same thing, I just live with it! (makes for a warm ride during the summer :roll: ) I'm gonna check this out now!

 

[sbwrench]

Re: Only hot air out the vents

OK, checked things out this am. Damper door was definetly in the open position. The cable is hooked up on both ends. It will pull the door open when I put the heat selector on hot but won't push it closed to shut the door. Anyway, I closed the damper door manually untill I can see exactly what's causing what. Thanks for the info, as always you guys saved me a lot of time.

 

[SY2932]

Re: Only hot air out the vents

Check to make sure that the housing around the cable is anchored securely on both ends. If it isn't, the cable won't have anyhting to "push" against and will only operate the door in one direction.

 

[jjorgensen52]

Re: Only hot air out the vents

New London isn't half bad, but it's not home either. There is a local hot rod fabrication place I found about a week before I left so I might be hanging out there next year :tup:


As for the cable not closing the door, that's probably the lever not working properly. It's a little plastic ring with a pin on it and it can get all screwed up easily. They're expensive to buy from GM but I replaced mine with junkyard parts without trouble.

I would guess the cable retainer that holds the casing is broken. The cable will pull fine because the casing is anchored at the duct end, but it won't push the door to the A/C side because it just pops out of the bracket. There is a red tab that holds the end of the cable and it will probably move around in there if it is broken

EDIT: Danggit Mike you beat me to it :lol:

 

[sbwrench]

Re: Only hot air out the vents

Yeah, that's exactly whats happening. I can see where a previous owner tried to "fix" it with some stacked up washers and screws. I see that whole control housing is pretty pricey. At least I have the door closed now. Probably won't need heat in So Cal for oh about another 7 months or so Thanks again for the help.

 

[sbwrench]

Re: Only hot air out the vents

Update: Armed with that helpful info it took me all of 2 mins. to do an at-work parking lot repair. The red clip on the control panel side had come astray. One self tapping screw and I'm back in biz! You guys rule.

 

[4C FED]

Re: Only hot air out the vents

Yeah, that's exactly whats happening. I can see where a previous owner tried to "fix" it with some stacked up washers and screws. I see that whole control housing is pretty pricey. At least I have the door closed now. Probably won't need heat in So Cal for oh about another 7 months or so Thanks again for the help.

Watch EBAY or get one from the wrecking yard.
http://cgi.ebay.com/ebaymotors/88-93-S-10-S10-A-C-Heater-Controls_W0QQcmdZViewItemQQcategoryZ33545QQihZ007QQitemZ170120973163QQrdZ1

 

[SY2932]

Re: Only hot air out the vents

EDIT: Danggit Mike you beat me to it :lol:

Heh, I'm glad that I'm not to only one who has spent WAY too much time in/under these trucks

!