Can someone help me out with an AC problem on a 1996 Ranger. The AC works fine when in the AC position but if I want to try to cool the truck down faster and set the AC to Max all I get is hot air. It sounds like a vacumn line problem to me but I have not found exactly what needs to be changed.

JR in Dallas

 

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Check the blend door control arm!!!!!

 

Thanks for the reply. After checking it more closely, it seems to only come on hot when the car is moving and the control is set to Max AC. Seems to work fine in both AC and Max AC when the car is idling. I need to dig out my old vacuum meter and check for vacuum in several places I guess. I did take the radio out and inspected the hoses. Did not see any apparent breaks. I also check the vacuum hoses under the hood. Since it works under certain condidtions I do not think it is a blend door. What do you think?

 

well when the control is set to MAX AC, the door has to set itself to recirculate only the in cabin air & you say in this position you only get heat.

 

I need to go drive the truck with the glove compartment open and watch what happens (maybe I should get someone else to do that while I drive). With the car idling in the drive way the recirculate door is open (although it opens very slowly when I switch to Max AC). I think as soon as I put the engine under load it will close due to a loss of vacuum. Anyway that is my theory. thanks again for your reply.

 

Ok good observation, it would seem then the control arm isn't damaged/broken, which is a common problem on our Rangers.

So you might indeed as you've suspected, have a system vacuum leak.

Question now is where in the system is it & how to successfully find & test for it?????

From your description of how slowly the door moves, I might first suspect the vacuum motor's diaphragm is leaking, as it's the thing most used/flexed & most likely to fail mechanically IMHO.

You might be able to hear the vacuum leak, if you place a length of tubing, one end to your ear, the other around the suspected part/s & listen to the "hiss" of a vacuum leak.

Let us know what you find.

 

Ok, I checked it with my gauge and at idle I only get only 5 inches of vacuum pressure. it seemed low only 5 inches of pressure. I have identified that I am loosing pressure after the Y where one lead goes to the vacuum motor. Therefore the leak must be between the Y and the white line that goes to a connector on the firewall and the other side of the fire wall. It got dark and I was not able to trace the lead through the firewall into the engine compartment. Any hints as to what to check? This is a 96 Ranger extended cab four cylinder 2wd.

thanks for your help.

 

have located the trouble. It is something called a diverter valve vacuum motor. Evidently it has something to do with controling the hot water feed to the heater core. Anyway, when I removed the vacuum line from this device and plugged that line the AC and Max AC work great. Evidently there is a vacuum leak in this device. Will try to order a replacement on Monday and I should be in business. I am glad I found it because it came apart as I was taking it off. Had that happened on the highway, I would have lost all radiator fluid and been stranded.

Again thanks for your help pawpaw. I helps to have someone to discuss the problem with.

 

Allright, good find & feedback.

In the meantime you could interconnect the two heater hoses with a short section of the proper diameter pipe & be able to drive it until the repacement part arrives. don't think your likely to need heat, this time of year!!!! LOL

 

found the part today at the local auto parts place. Had it in in about 5 minutes and everything works great. They called it a heater control valve.

 

Interesting piece of information freerange, I had never considered the heater control valve affecting the blend doors movement. I'll have to file this one in my memory banks!!!! On second thought at my age I better write it down!!!!!LOL

 

pawpaw, I don't thinkthe heater control valve has anything to do with the movement of the blend door. Instead, it sounds to me like the valve wasn't shutting off the hot coolant flow to the heater core like it was supposed to, and hence the cool air from the evaporator core was being blown through the hot heater core, resulting in the warm air at MAX A/C.

 

Well maybe I read something into the vacuum troubleshoot, that wasn't there!!!!

I thought he posted that the problem was with a internal vacuum leak at the heater control valve & that leak was affecting the blend doors movement.

The interesting part for me was I didn't know the heater control valve had a vacuum connection to it!!!!!

Maybe on my 99 it doesn't, I've not yet looked, as the wife just got home with the Ranger & it's dark outside. LOL