Heater A/C Blower problem

[superduty]

97 TJ, but many many years ago I switched out to controls, wiring and heater set up under dash to parts from a 2000 (I think that was the year I used). So, it no longer has the levers.

I know there are a million threads on heater issues. I couldn't find one that was my exact issue.

The problems I am having are intermittent. I can't seem to find any particular scenario where the problems shows up.

Sometimes everything works as it is supposed to.

Sometimes you turn on the heater or AC and nothing works. When this occurs, everything seems to start working within a minute or two of starting the Jeep.

Sometimes you turn on heater or AC and the fan blows on the same speed regardless of setting 1-4. The speed it blows on is definitely NOT the high setting.

The selector knob on the right always seems to work correctly in terms of what vent the air is coming from.

Yesterday, a new issue showed up, where turning the dial to hot produced no hot air (at the same time the blower was blowing the same speed regardless of setting). This morning the center dial worked for heat. (The problem is NOT the heater core or flow of coolant).


I could start throwing parts at it, but if I can narrow it down that would be great. I suspect it is the left and center control knob/switches that are the problem?

 

[Mac57]

Not being exactly positive what you have installed, here are a few things to look at. Check for vacuum leaks on the lines leading to the control panel. Loss of fan speeds usually involves a fried blower motor resistor. Replace it AND the blower motor, the aging motor can increase the electrical draw. Also check the back of the knobs themselves, sometimes the round piece that fits over the metal switch post control splits apart so you end up turning the knob but the knob is not gripping the metal switch post and turning it.

 

[superduty]

Not being exactly positive what you have installed, here are a few things to look at. Check for vacuum leaks on the lines leading to the control panel. Loss of fan speeds usually involves a fried blower motor resistor. Replace it AND the blower motor, the aging motor can increase the electrical draw. Also check the back of the knobs themselves, sometimes the round piece that fits over the metal switch post control splits apart so you end up turning the knob but the knob is not gripping the metal switch post and turning it.

I have a stock TJ set up from either a 99 or 2000 (can't recall). Not gonna be a vacuum issue as that is the one part of the system that works perfectly.

Doubtful it is a fried resistor as it is an intermittent problem. In fact this afternoon all speeds were back to working perfectly.

I think I am going to start with inspecting the wiring and replacing the 3 knobs.

Turning the knob and not gripping the metal switch post makes sense as a potential problem.