HVAC vent to defrost uphill, cruise works

[Lowrange2]

Well, did it work??

I have procrastinated...

 

[Lowrange2]

Finally got to look at it. I found the arm that controls the top defrost flap backed out of its hole. I pushed it back into place but it's not going to stay. That only solved the low air flow on defrost issue. Tomorrow I'm going to replace the check valves in the vac line just see what happens.

 

[Lowrange2]

Click for video:

 

[Lowrange2]

^ I'm assuming that's the same issue the OP mentioned.

 

[Desert4x4]

Click for video:

Nice video. That's eexactly what was happening to mine. I just pulled the arm out, superglued it and stuck it back in.

 

[Lowrange2]

I'll be doing that asap. Mine popped right back out.

That obviously didn't fix my issue though. It did help the air flow out of the defrost vents though.

I tried to replace the check valve and that didn't help.

I'll be buying a mityvac tomorrow to do some more troubleshooting.

I'm afraid my leak is inside the dash.

 

[Lowrange2]

I broke down and purchased a Mityvac to help diagnose the issue. That allowed me to pinpoint that the issue was, in fact, in the dash. At this point I've only tested vacuum at the hose at the firewall going inside the cab.

As soon as I started pulling the dash apart I found this: (Nipple partially broken on the back of the HVAC controls) No, I didn't break it when I was removing it. It's been broken for a while. I'm assuming it was broken when the dash had been pulled apart in the past.

I did a quick repair on it with some hot glue to get my by until my replacment arrives.

Eliminating that leak fixed 90% of the issue but the Mityvac still shows a slow leak in the system inside the cab somewhere. I'll be further diagnosing the issue once my replacement HVAC controls get here.

 

[XJensen]

Thanks Guys. Great Info. Both My 2001 Have The Same Issue. I'll Look Into It Someday....

 

[Lowrange2]

Thanks Guys. Great Info. Both My 2001 Have The Same Issue. I'll Look Into It Someday....

It's been driving me crazy for over a year now. I'm determined to fix it now. lol

I noticed that mine primarily had the issue when the selector was on AC (Recirculate). It didn't do it nearly as bad on the heater settings.

 

[GordoSmasho]

My defrost only works on the lowest fan speed. As you turn the fan speed to 2 you can hear a flapper in the dash shut and and the defrost air stops. I have to turn the fan back down to 1, and the selector to the off setting, and then put it back to defrost to get it going again. Does this symptom sound like a side affect of what you guys are talking about?
I figured it was harder to get to so i havent worried about it. But it was rough last weekend wheeling in the rain and having almost no deffrost.

 

[Lowrange2]

My defrost only works on the lowest fan speed. As you turn the fan speed to 2 you can hear a flapper in the dash shut and and the defrost air stops. I have to turn the fan back down to 1, and the selector to the off setting, and then put it back to defrost to get it going again. Does this symptom sound like a side affect of what you guys are talking about?
I figured it was harder to get to so i havent worried about it. But it was rough last weekend wheeling in the rain and having almost no deffrost.

That sounds like you have an issue with that flapper I was referring to earlier. You can access it by pulling the radio out and looking in the back left bottom corner. More than likely the rod/pivot piece is not connected to the flapper.

 

[GordoSmasho]

I will be doing that this week. Thanks

 

[Lowrange2]

Also, if you look straight to the back of the compartment you'll see the ductwork. The duct is split right there and has a piece of foam between the two pieces. If you push the top piece in a little bit you'll be able to see the door that opens and closes when the defrost is selected.