Help, this has me baffled. AC works fine under normal driving, but under very hard braking it switches completely to hot. Anyone out there with a similar problem and solution?? Same air flow out the face ducts, just goes from full cold to full hot. 2001 Dodge Ram 1500 V8

1. Replaced - ac/heat control assembly based on a shop diagnosis - this was not the problem & wasted $100.

2. Vacuum related - seems opposite, if vacuum check valves are leaking, then problem may show up in cruise control, or switching from face to defrost which is the saftey mode. There are 2 check valve under the hood from the manifold "T"'s to the cruise and the "T"'s to the HVAC thru the firewall.

3. Compressor seems to stay on, pipes are cold, had system charged.

4. Engine coolling fan stays engaged (belt driven with no aux. condenser fan)

So any ideas, where is the blend air door located? How to check easily??

Seems like the deacceleration somehow causes the blend air door to go from cold to hot position. Any help in solving this would be appreciated.

john

Help, this has me baffled. AC works fine under normal driving, but under very hard braking it switches completely to hot. Anyone out there with a similar problem and solution?? Same air flow out the face ducts, just goes from full cold to full hot. 2001 Dodge Ram 1500 V8

1. Replaced - ac/heat control assembly based on a shop diagnosis - this was not the problem & wasted $100.

2. Vacuum related - seems opposite, if vacuum check valves are leaking, then problem may show up in cruise control, or switching from face to defrost which is the saftey mode. There are 2 check valve under the hood from the manifold "T"'s to the cruise and the "T"'s to the HVAC thru the firewall.

3. Compressor seems to stay on, pipes are cold, had system charged.

4. Engine coolling fan stays engaged (belt driven with no aux. condenser fan)

So any ideas, where is the blend air door located? How to check easily??

Seems like the deacceleration somehow causes the blend air door to go from cold to hot position. Any help in solving this would be appreciated.

john
John

I am having the same problem on the same truck. I have located the blend door actuator that is located on the bottom of the housing. It has a plug that powers it. I have unplugged it to see if it will stop the problem. I will keep you updated after I test it for a day. If this works I will try to remove it without taking out the housing. It has a couple of phillips screws. One is easy the other might need an offset screwdriver. I am glad I am not the only one. Misery loves company. Derek

Let me know. I agree the blend air door is electric operated. The service manual says take the dash off, remove the HVAC unit from the top. I took the easy screw on the actuator out and gave up with the back one. Let me know if you are able to get the rear one out from the bottom. Maybe not enough room to disengage from the shaft to get it off. What a lousy design.
On mine, changing the temp knob - from cold to hot or vis versa, the actuator moves but does not settle in to a set point. At full cold, it keeps rotating. It should reach a stop point, maybe the actuator is ok but a coupler or cam to the door shaft is cracked. If I could just lock it in the ac position, it would be helpful. Plus I do not know why the hard braking affects the door, unless it is just momentum.