I got cruise control. I got a smooth idle. I got no whistling or hissing noises. What I don't got, however, is HVAC directional controls. It's stuck on defrost and sometimes I can get it to transition maybe halfway to the vent it is selected to. I have checked the black hose leading into the dash for cracks. I have removed the glove box and checked all the vacuum connections behind it. Is it possible the controls themselves are bad? I am out of ideas at this point.

 

Oh yes. That mode selector is a rotary valve that is known to leak. You can take it apart, careful you don't lose the little ball and spring, clean and/or polish the contact faces, lube it with Vasoline, and put it back together. Chances of finding a new one is like finding rooster teeth.

 

$291 wow

https://www.summitracing.com/parts/s...1/applications

 

My 96 Sport was stuck on defrost as well. I figured I had a bad vacuum source so the 1st thing I did was bypass the check valve situated on the aft side of the intake manifold. I removed the valve and slid the system supply hose directly onto the hose barb on the manifold where the valve used to fit. That got me my selector back. Then I noticed that the plastic vacuum tubing that goes from inside the truck to the selector valve just forward of the firewall was looking kinda kinked. I tried to bend it back and it snapped. Wonderful. I went to Advance and bought some rubber tubing to mend it. Thinking that might have been the restriction causing the lack of selector control I reinstalled the check valve. Nope. The problem returned with the check valve so off it came and the hose went back onto the hose barb.

 

Get a hand operated vacuum pump and try to pull vacuum on the inlet hose at the back of the controls. That way you can isolate the leak to upstream or downstream of where the hoses meet the controls. Even though you have inspected the small black tube that goes into the firewall, the check valve could be bad. My check valve failed and caused my vent selector not to work when under heavy load. Put the vacuum pump on the check valve also, don't just blow through it. My valve seemed okay when blowing through it but would not hold sufficient vacuum.

Those vent selector plates can be had a dime a dozen at salvage yards.

 

I had the same problem and I followed the black vacuum hose and found a small crack in the hose right at the battery area before it fed down to the vacuum ball. A little electric tape fixed it for now. 89 model.

 

Electrical tape often won't last. (Sometimes you get lucky.) Liquid electrical tape works better.

 

Thanks guys! I'll check the valve first and then take apart the rotary dial. Maybe I can pick up a vacuum pump later this week when I run into town.

 

In a pinch, a vacuum cleaner works, LOL!

 

Well, valve was good. Started taking apart the rotary valve and when the white cover came off, the spring shot out of it. Apparently there is a ball? Not sure what it looks like but I guess I'll try to find it now.

Edit: I found it.

 

Well, cleaned everything up and applied Vasoline everywhere. Dial turns a lot smoother now but still nothing. I can redirect it to feet and have some come out there but still nothing coming out of the face vents. Maybe I should tear the dash out like I'm doing a heater core swap (again), or either go to the boneyard and try to find something there. I'd think I'd rather do the latter before tearing out the dash.

 

Found one on ebay $20, 1 day left zero bids

https://www.ebay.com/itm/2001-01-Jee...0AAOSwTpldxV1c

 

Thanks, but I do believe 99-01 HVAC controls are slightly different from 97 -98 ones. Mine has a cable and that one is electric.

 

Do any of yall have pics of where the spring and white ball go in, mine just fell out not sure how it goes back in!!!