I've got a problem with my heater control. I either get full hot air or full cold - nothing in between (as in warm air). You can set it to heat (all the way clockwise) and you'll get full hot air - but as you turn it the other way towards the colder settings, the temp does not change until you are at full cold. What would cause my temp control to only give me the hottest or coldest settings only - I want warm air! Can anyone point me in the right direction?

 

I have bypassed my heater core (AZ car - no heater needed!), but can say that it's probably due to a malfunction with the heater core control valve located under the dash right near your right foot. When this valve starts to go out, the rubber bushings that seal the piston will corrode and cause the piston to stick in the chamber. Once this happens, when you shift the rotary dial control from hot to cold, it only moves the piston when you get it all the way in it's travel - in other words, the piston isn't moving gradually, it' moves all or nothing. There is a spring on the back of the rotary dial control on the dash that smooths the travel of the cable going down to the control.

When mine went out, it was sending hot coolant past the O-rings on the piston right onto my accelerator pedal foot - giving me the HOTFOOT! Problem was, this flow is greatly increased the more engine RPM it's running, so the more gas you give it, the more hot water gets sprayed onto your foot!

 

Thanks Longduck - you've described exactly what my problem is (other than the leaking coolant). Can you help me pinpoint where this valve is? Is it in the shop manual?
thanks

 

I have a somewhat similar problem.... in the winter time, when i'm in the highway and it's really cold out, somehow the cool air gets through the vents, specially on the passenger side. the heater still works, but on the passenger side the cool air supercedes it.

 

First post - being helpful!

 

Second post - being twice as helpful!

 

Third post - really helpful, now!

\Northern7 - the heater core valve is in the FSM, but I forget which section; check 'Interior'. Changing out this valve is a total PITA, however, since there's not much room, you're on your back, and the metal lines are connected with rubber hoses and clamps that somehow never point where you can get a screwdriver.

Check the VB catalog for the visual image, but the location is right there next to your accelerator foot. In fact, it's within about 2 inches and you should be able to see the metal wire rod that operates the lever on the piston and where the springs are located for tension control leading up to the rotary dial.

RioFrio - your problem sounds more like ducting that has come loose under the dash. I you take your vent off on that side (single x-head screw on the bottom pointing up), you should be able to look down there with a flashlight and figure out what's up. HTH,

 

Well I checked the linkage and everything seems to be moving the way it should - there seems to be full motion or stroke with the selector lever with no binding. The good news is there are no leaks in the piping - the bad news is I can't figure out why I get either very hot or very cold air only. I'll have another look at it on the weekend - maybe the cable (control wire) needs to be adjusted.
Longduck, thanks for the help - you're right about the lack of space to work - flat on your back with a flashlight in your mouth