On my 97 daily driver my heater seems to have taken control of my air conditioner... No matter what I have the temp set at, and regardless if I have AC or Heat selected, I only get FULL HEAT temperature (regardless of outside temp). My fan selector works correctly and the ac compressor will cycle correctly, but no cold air will ever come out. There seems to be a funny "catch" in the temp selector **** at about the 1:00 position when rotating clockwise (but not counter clockwise). Also, with the truck running and AC selected, when i reach under the black evaporator (or is this the condensor?) cylinder from under the hood, I can feel all my beloved cold air blowing out throught the firewall ...trying to keep my engine bay cold I guess... I checked my AC charge and it is good. The only other variable is that last summer, in my passenger side floorboard, condensation kept soaking my carpet. I located that the source was where the black plastic ducting goes throught the firewall... So, I siliconed that all up to keep from soaking the floor and have only recently started to get a small leak in the same location again (it is hard to stop a leak from the inside). I've done a ton of research on this subject and almost had myself convinced it was a blend door problem but everyone who seems to have this problem can at least get max cold and I havent found anyone who only had max heat...

Lots of info, but I sure hope someone can help me... Summer is approaching fast and, as it turns out, it gets extremely warm in Texas in the summer...

Thanks in advance

 

Sounds like a blend door problem to me. Maybe the switch, or maybe the controller board. Could be the little piece that connects the blend door to the control board.

 

Thanks. Is there any way to check the switch or the controller board? Also, despite all the research I've done on the blend door, I still can't seem to find the stinkin' thing on my truck... I may be staring right at it, but I can't find it for the life of me. The underside of my dash has a molded piece of thick black plastic denying any access to the components located above. Any advice?

 

If you are leaking onto the floorboard you need to make sure the drain outlet isn't plugged with gunk. Siliconing around the firewall will just seal the moisture into the housing.

The blend door malfunctioning is my next guess. First though, I would make sure the vacuum lines behind the controls are in good order and hooked up. Switch them around a little right after shutting down the truck and listen for changes in movement. If that doesn't help pull the dash bezel and then the control panel for the A/C. Its not a big job.

Cold air blowing into the engine bay sounds like a blend door to me though. The actuator arm has probably become unhooked or broken in there.

 

on bump,

Try removing the glovebox and looking at it thru there.

 

"I would make sure the vacuum lines behind the controls are in good order and hooked up.

- Do you mean the vacuum lines near the throttle linkage under the hood?


"Try removing the glovebox and looking at it thru there."

-I removed the glovebox earlier today... Is that flap that I see immediately behind the glovebox the blend door? If so, I was able to make it operate when I switched my AC control to recirc. I thought this flap/ door was only for recirculating the in-cab air... You can see my dilema. I'm not an AC guy by any means

Thanks for the help

 

"Switch them around a little right after shutting down the truck and listen for changes in movement"

-Oh... you mean the AC controls. Are the vacuum lines hooked in behind there?

 

The blend door on your 97 is cable operated. It's a pretty simple system. By your description, I think your temperature **** may just be broken and not turning the shaft. Just pull the **** off and have a look. It should be a round hole with a flat.

Also, if you turn the **** fairly aggressively from full cold to full hot and back, you will be able to hear a small thunk as the blend door hits the stop at each end, if it is adjusted right and sweeping fully.

Next, you should be able to pop out the HVAC control head and look at where the cable attaches to the blend door lever on the top of the HVAC assembly. Move the **** back and forth, and see if the cable moves the lever each way.

Hope this helps.

 

"Next, you should be able to pop out the HVAC control head and look at where the cable attaches to the blend door lever on the top of the HVAC assembly. Move the **** back and forth, and see if the cable moves the lever each way."

-Thanks for the help. Where is the HVAC control head (I am assuming it's the set of ***** on the dash...) and HVAC assembly and how do I get to them to inspect?

Also, both of my control ***** were cracked inside but not totally broken. I went ahead and replaced them a few days ago but that wasnt the problem.

 

Ok, so after removing the AC control head, I found that everything is in working order behind the control head itself. After further investigation, I found that the cable that apparently opens and closes the blend door, has gotten disconnected somehow (from the blend door end). Now I can't for the life of me figure out where or how to reconnect it. Any help is greatly appreciated.

 

I failed to mention that this cable is connected to the temperature **** on the control head. I'm begining to think that this cable doesn't connect directly to the blend door.... maybe it connects to a thermostat or temperature control lever???

 

Have you owned this truck from new if not did the temp control ever work? I ask this as I believe a 1997 truck should have electric temp controls, I think the boden cable was last used in 1995. Someone may have changed the control panel for the wrong one. Either that or it was changed over to a cable system and the cable has become disconnected.. As was previously mentioned check your drain to ensure it is clear and condensation is draining from it.

Have a look on the passenger side floor next to the hump on the bottom of the heater plenum there should be a little black electric actuator that is attached to the blend door shaft. If you have that, you have the wrong control head.

 

I haven't owned since new, but the temp control has worked fine for almost 2 years now. There is not an electric actuator attached to the blend door shaft. There is vacuum operated actuator connected to it. The blend door operates correctly (by hand) and the vacuum actuator seems to be functioning correctly (when I pull a vacuum with my mouth)... Someone may have changed it over at some point, but if they did they did a remarkably professional job as everything looks very seemless.

 

Sorry about the mis info Newagain, I missed that your truck is a 97!

 

Hey sometimes bad info is better than no info!!