Temperature Control Knob
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Temperature Control ****
Hi all,
I've used this forum considerably and have learned a great deal so I wanted to share something that solved a recent problem of mine.
I've owned my 1999 Durango with the 5.2L for a bit over a year now and the heat was never anything more than lukewarm. I flushed the heater core based on posts here and got some crud, but great flow in both directions. At operating temp both hoses were hot. Still no real heat. When the evap coil went out this summer (2013) I had it as well as the heater core and coolant replaced. The A/C worked great, just very low heat again this winter.
My upper hose never built up any pressure and replacing the radiator cap fixed that, but still lukewarm heat.
The only other thing that made sense was the blend door in the HVAC box, but that always *seemed* operational. The mechanic just had the whole box out a few months earlier and if he found it broken he would have replaced it. When I started testing it based on the dial operation, however, I found the problem shown in the attached pics.
The dial itself has a little tab that runs in a channel that causes it to stop at either end of the blue/red spectrum printed on the cover. What I found in my case was that the blend door control cable was a bit out of adjustment.
The position of the blend door in full-cold position stopped the dial too early. The door was seated closed in the box where it should be but the dial could not turn any further. When turning to full-heat mode, however, the dial tab's channel stopped the dial at the end of the spectrum, but the blend door had not reached the full-heat position.
If you set the dial at the 12 o'clock position, you can pull it off of the shaft. Seating it slightly back on the shaft allows you to spin the dial as much as you want and it will stop when the blend door is seated at one position or the other. Just don't turn too hard as I imagine you could break the cable or the blend door.
I've got great heat now with the dial well past the end of the printed spectrum.
Thanks to everyone for their dedication to these vehicles and I hope this can help someone.
-John-
I've used this forum considerably and have learned a great deal so I wanted to share something that solved a recent problem of mine.
I've owned my 1999 Durango with the 5.2L for a bit over a year now and the heat was never anything more than lukewarm. I flushed the heater core based on posts here and got some crud, but great flow in both directions. At operating temp both hoses were hot. Still no real heat. When the evap coil went out this summer (2013) I had it as well as the heater core and coolant replaced. The A/C worked great, just very low heat again this winter.
My upper hose never built up any pressure and replacing the radiator cap fixed that, but still lukewarm heat.
The only other thing that made sense was the blend door in the HVAC box, but that always *seemed* operational. The mechanic just had the whole box out a few months earlier and if he found it broken he would have replaced it. When I started testing it based on the dial operation, however, I found the problem shown in the attached pics.
The dial itself has a little tab that runs in a channel that causes it to stop at either end of the blue/red spectrum printed on the cover. What I found in my case was that the blend door control cable was a bit out of adjustment.
The position of the blend door in full-cold position stopped the dial too early. The door was seated closed in the box where it should be but the dial could not turn any further. When turning to full-heat mode, however, the dial tab's channel stopped the dial at the end of the spectrum, but the blend door had not reached the full-heat position.
If you set the dial at the 12 o'clock position, you can pull it off of the shaft. Seating it slightly back on the shaft allows you to spin the dial as much as you want and it will stop when the blend door is seated at one position or the other. Just don't turn too hard as I imagine you could break the cable or the blend door.
I've got great heat now with the dial well past the end of the printed spectrum.
Thanks to everyone for their dedication to these vehicles and I hope this can help someone.
-John-
