A/C Vacuum Problem

[SuzaMan1957]

95' 2.3 Ranger. When I accelerate or engine is under a load(driving on an upgrade) the air flow ceases to the vents and air flow is sent to defrost vent. I've checked the vacuum reservoir and it is holding a steady vacuum. I placed a tee in the vacuum line that runs into the cab and attached a vacuum gauge to monitor the vacuum being supplied to the cab. Here are my observations. When I put the switch in the A/C position vacuum holds steady and flow to vents is uninterrupted. When I switch to the Max A/C position I start losing vacuum. When accelerating or under a load I lose air flow. When I decelerate, flow and vacuum go back to normal. I also have noticed that i used to hear a change to air flow when changing from Max A/C to A/C, now I don't. Any thoughts on what my problem may be?

 

[SuzaMan]

Hmmm, I'm just guessing but I think I may have a problem (leak) with the control switch or just may have a leak on the vacuum line (white) that runs from evaporator casing to the recirculating door vacuum motor.

 

[v8318cid]

Definitely a vacuum leak. The recirculation door (which closes in MAX A/C mode) is powered by vacuum. Cannot confirm the other door actuators, but I suspect they are vacuum as well. Either way, you've got a problem. Either a leak exists somewhere in the vacuum tubing (including the vacuum reservoir), or your engine isn't producing enough vacuum due to incorrect timing or similar issues.

 

[SuzaMan1957]

I'm getting plenty of vacuum to the reservoir 20 inches. The reservoir is holding, no leaks. There is one vacuum line (black) that comes off the reservoir to the firewall and then on the other side (inside cab) there is a manifold (I'm guessing) that splits it into 2 (white & black) vacuum lines. The black continues into the Evap. case. The white tees to the Max. door vacuum motor and then continues to the Evap. case. I'm not sure whats going on inside the Evap.case. I put a hand pump on the Max. vacuum motor and its working fine. I guess I've ruled out a malfunction on the control switch because I'm losing vacuum when I switch to Max. A/C and the Max. recirculating door is not closing. A leak in that white line is probably my problem.

 

[edawg]

Similar issue with me.

What I'm experiencing is very similar (in a 95 Ranger) however, the air swithces to defrost randomly. The vacuum motor for the recirculation door does not operate and I can feel there is no vacuum from the Heater/AC controller in the dash to the vacuum motor when I swith the controller to Max AC (White vacuum line). I took the Heater/AC controller out of my 96 Explorer where I don't have this issue and put it into the Ranger. The problem still exists in the Ranger. Also, all other functions that appear to utilize vacuum through the Heater/AC controller appear to work properly. There are actually two lines that come through the firewall and mate with the black and white lines inside. My problem is I can't find a good diagram to use, and I can't find those vacuum lines inside the engine compartment. I'm a pretty well rounded individual and can generally troubleshoot and repair most issues with a Haynes, and Chilton's, manual but I'm honestly ignorant when it comes to vacuum issues. Any pointers would be greatly appreciated.

Thanks,

 

[edawg]

Update - I found there was a leak between the "T" at the recirculation door, and the line going out to the heater core vacuum motor. I haven't isolated the specific cause of the leak yet but after capping the line off past the "T", the recirculation door started functioning.