Weird AC Problem

So I recently repaired my climate control and put in a new wire between the circuit boards. (I accidently ruined the old wire attempting to change bulbs) After putting everything back together and plugging in the harnesses I checked to make sure everything was working and gauge lights came on, the fan came on, vents worked properly, ac came on and seemed to work fine (blew cold air) but after a short while of driving the air turned hot and it never returned to cool. Even turning the fan off noticeably hot air seemed to be coming through the vents. I checked all fuses and they are fine. The AC is definitely on the whole time because I can hear it still cycling in the engine. I unplugged my battery doing some work with my stereo and started up the car again and it did the exact same thing. I'm really scratching my head here. Everything worked perfectly fine beforehand. Any help or suggestions please?

 

My 98 does something similar. In my research here I have came across many different things. Easy one first. Take off glove box and check your linkage for the blend door. Next is (requires two people) move the temp control from cold to hot and watch the bypass valve located in the middle (mine anyway) and you should be able to watch the diverter switch go back and forth. Funny thing is all my stuff functions properly. My AC doesn't get to cold. If I leave the fresh air on and my fan off hot air always comes out of my vents even when the setting is on cool. Like it's not taking cool air from outside into the cabin. Driving me nuts!

 

check if Freon is low before getting into looking at anything else.

 

if you have the AC off and the fan off and the recirc switch to outside air why would low freon do that? In the OP's initial thread he is stating this happening. Hot air still coming out.

 

That would be a odd coincidence. I was still using the AC in October. I will check. Why would hot fresh air be coming out through the vents when turned off though? Moving the temperature knob changes nothing. Not even from warm to hot. It's just plain HOT air. I've never noticed this symptom with low freon before.

 

the way our trucks are designed, they don't have extra defrost vents on the side of the dash to defrost the side windows so it uses the outside vents to defrost them so they blow anytime defrost blows.

when the rec button is off it allows outside warm air to pass through the ducts and out of these outside vents as well as the dash windshield vent.

next time you drive along try it out, turn rec on and no air, turn it off and air blows. the thing is the ducts are always going to be picking up warm air from the heater core even when heat is turned off so the only time the vents don't blow warm is when the a/c is on.

hope that helps.

 

no, he was saying this happens when the a/c is on and it stopped cooling, that would be a symptom the compressor had turned off

 

So when I hit the Recirculating button it makes no difference. Also I have to emphasize this air is HOT, Not warm. It will make me start sweating if the windows are down without the fan even on. Regular vent air never felt this HOT. Warm yes, I understand that. After a ton of searches I find a possible cause. "Stuck blend door" It can be stuck in a hot or cold position. Mine maybe stuck in a hot position not allowing normal "cool setting" ventilation or A/C air to come through. Other idea might be a actuator problem.

Also forgot to mention my compressor and lines were replaced a year ago because of a accident. It's all brand new in the engine bay. I felt the lines when the compressor was running today and one was icy cold and the other was warm as they should be. I REALLY don't think the issue is in the engine bay.

Check out this video. I just have to get around to taking the dash apart again.

 

I have a 98 Taco with the same problem, here is what I found. If you reach under the duct located in the center behind the radio and climate controls you can feel the cable running from the temp knob that opens and closes the blend door. The temp knob also has a second cable that opens and closes the heater control valve. My guess is either your blend door cable or heater core cable is sticking. You can move the blend door cable by hand if you help it along with the temperature knob.
I ended up putting some lithium grease on the cables and working them by hand until they moved using just the temp knob. Good luck, hope this helps!

Gary

 

sounds like the a/c is working fine, I agree it may be the blend door but it could also be the heater valve under the hood is open which turns the heater on. even with the blend door open it shouldn't be hot unless the heater valve is open. this is the only thing under the hood I want you to look at, and its easier to check this first before taking the dash apart. if its blowing "hot" air, then for sure the heater valve is open and you will need to figure out if its open because its broken, or if its being told to open.

 

So I Let this go through the winter and I'm finally getting back to trying to solve this issue. So I did all the diagnostics possible in the engine bay and I determined the problem is definitely not there. I took the glove box off and started looking around for a lever that would open and close the blend door. While taking things apart, seeing nothing and getting frustrated I did some more research. I located the blend door actuator aka the vent flap motor aka the servo damper. I decided to take it off to see if I can locate a cable of some sort. It's located below the bottom left of the glove box. It has 3 screws. The rear screw is very difficult to get at so I ended up snapping it off. Didn't really care at this point. After getting the servo damper out of the way I located the cable and assembly for the blend door. Turned on my a/c and manually pushed the lever the opposite direction it was stuck in and the COLD AC came through the vents!!! So I'm thinking the servo damper isn't working correctly so I tested it out and the arm moves that pushes the lever but I don't think it moves enough to push the lever where it needs to be. I'm thinking I must have damaged it somehow during my climate control bulb replacement when I didn't disconnect the power and it was turning on and off. BIG LESSON learned here! So I think a Faulty servo damper is the problem. I took it apart and it has a small motor in it. I'm going to find out if I can get a replacement. Otherwise a new servo isn't that cheap!

 

So after running some more tests on the servo damper I believe it's working fine. Ran 12 volts to the unit itself and it seems to operate correctly. Put it back in and watched it try to move the lever I manually moved to open and close the blend door. It would not move the lever enough to fully open the door. So I'm completely stumped at this point. Could the problem be somewhere else or is the servo damper not rotating fully? Does anyone have a video of how it should move? Any tips would be greatly appreciated! I cannot find anything on this topic anywhere. No youtube vids. Nothing. I can manually open and close the blend door but not electronically.

 

I still haven't fixed this issue. For the summer I manually moved the cable in the cold position so the A/C will function properly. Is there a second servo damper? It seems the one I took out is working properly but if there is a second one under there that assists the other in moving the lever that might be the problem? Some one has had to have had this issue..

 

Instructings to check servo motor

 

I was in this thread in 2015 and I still haven't fixed mine. haha I just reach down and move the arms manually in the passenger floorboard area. Pain the ass. I contemplate taking the dash apart and replacing my entire HVAC unit. There is a rod that is completely broke off the mounting point for my HVAC unit. I am assuming about 10 years ago somebody had the servo motor malfunction or a cable got stuck and they broke it trying to figure it out.