Defrost knob hard turning

[larrybojac]

Hi guys and gals...

Has anyone else noticed this on their PT .... "with the mix control is in full defrost position, and the fan is in full high position, moving the selector out of the full defrost position is tough"?

It's like air pressure is holding it there cause when you reduce the blower speed the knob turns fine, with what I'd call a more "normal" amount of force. Just curious.....

Larry - 03GT

[Jeff V]

Read the manual,it's explained well in there... something about a mechanism that only allows fresh air if you want to defrost/demist.

[larrybojac]

Hi Jeff...

I know what you are saying, and I do understand there is an interconnect linkage between the mix (mode) control and the fresh/recirculate control. Anytime you move from normal a/c or heat to the "mix" or "full defrost".. you can see that recirc control move to the fresh position... where it should be for more effective defrost/de-misting.

That's _not_ what is causing the mix control knob to be tough to turn from the full defrost detent. It is really like there is not enough mechanical advantage through the knob and it's associated linkage to overcome the _airpressure_ that is working against the deflector door. Like I say, turn the fan speed down and the force required becomes more normal. Only notice it when moving the control away from full defrost with fan speed on high. Weird... there is nothing else to make me think that something has become dis-connected... which is not that uncommon in heater controls.

I've read the manual.... it's not our first rodeo. <G>

Larry 03GT... (wife complained about tough turning knob - she thought she might break it ... took more force than expected. I agree with her.)

[05cruiser]

Originally Posted by larrybojac

Hi guys and gals...

Has anyone else noticed this on their PT .... "with the mix control is in full defrost position, and the fan is in full high position, moving the selector out of the full defrost position is tough"?

It's like air pressure is holding it there cause when you reduce the blower speed the knob turns fine, with what I'd call a more "normal" amount of force. Just curious.....

Larry - 03GT

Although I haven't experimented..yet.. with the relationship between fan speed and resistance, I have noticed that it can be hard to turn the mix knob between the defrost and normal positions. My '98 Grand Caravan mix knob has very little resistance, and I assume it is using a vacuum switch or something. My PT definitely has mechanical linkage that puts up some resistance. Since mine is a 2005 I can only assume this may be a problem down the road as the linkage stiffens up, grease dries out and/or gets dirty. I wonder if some of the group with older PTs have had issues?