I just replaced my blower motor resistor and it seems as if I can't get it to seat properly. I can only get it to blow out of the defrost vents now and I feel air around the resistor making me think that it's leaking there. I had no issues prior

 

Leaking around the blower resistor and air only flowing out of the defrost vents are unrelated.

If you can't fit the resistor in properly perhaps it's the wrong one for your '99.

For the defrost issue, open this link and scroll down to post #51.

https://www.cherokeeforum.com/f2/gre...e-6558/index4/

It shows the vacuum lines in your engine bay. Examine each tube/rubber coupling, closely for cracks, chafes, and/or dis connects. If necessary, remove the battery to see the tube in back of it.

The vacuum reservoir under the right front bumper end cap can be accessed by laying on the ground under the end cap and pulling down the right inner fender liner.

 

I had a vacuum leak before and fixed it over the summer. I'm thinking it's possibly the switch? It leaks out of the the defrost vent and I can't find any leaks in the engine bay. Cruise control works and thev vacuum ball is fine

 

Do a leak check using a vacuum brake bleeder, as shown in that link I posted.

It could be a leaky tube at the climate contol panel but check the system using a vacuum hand pump. Harbor freight has them - cheap.

 

Does this switch look bad?

 

Bump

 

If you're talking about the brown stain by the fan speed switch, there is a possibility that the switch is toast. You can a buy Climate Control Panel on Ebay.

But, as stated before, the blower resistor fitment issue you have has nothng to do with the defrost issue.

 

Ok, it seems it won't get off defrost mode which is what makes me believe the switch is bad

 

The "Switch" would be the center **** on the Climate Control Panel. It's the Mode Selector. It does the vacuum selections for the HVAC door positions.

 

So would replacing the whole switch probably fix it,?

 

The Mode Selector vacuum control rarely goes bad. I would look for a leak to the manifold on the back of the Mode Selector before just changing the Climate Control Panel.

 

I hit a bump and now it works perfectly, does that make any sense? Once I turned off the car it stopped working

 

If you pull the Climate Control Panel out far enough you can see the Mode Selector vacuum manifold.

The black tube is the vacuum source from the engine. The Blue tube and the yellow tube are for the Defrost Door Actuator.







If you roll down the glove box you can see a quick disconnect for the vacuum tubes.



I know of one person on a Jeep forum that found the black vacuum tube chafed and split open between the quick disconnecct and the Climate Control Panel, where the tubes pass through a small opening in the dash frame.

The black tube goes from the vacuum manifold on the Mode Selector, over the top of the HVAC Unit and out the firewall to a check valve, then to the feed tube.



This tube has been found to be broken.



And fixed using a length of rubber hose.



Here's a schematic of how all the Mode Selector vacuum functions work.

Note that when vacuum is removed from the Defrost Door Actuator, the actuator is driven to the door open posion (position #5).

 

Awesome thanks!

 

Turns out the relay on the wiring harness in the glovebox was loose causing it not to work