1994 Jeep Cherokee Sport
4.0HO auto 4x4

Okay guys maybe it's just coincidence but a few issues have appeared since the cold weather arrived (this will be my first winter with this truck).

1) My jeeps cabin air system farts whenever I put it on Heat. Now I say fart becauses it sounds just like it and is just as brief. Just a real short, I had too much TacoBell, maybe inferno sauce wasn't a good idea FART.
Also in Heat lots of noise from below my glovebox but no air coming out whatsoever. Though when I put it in defrost it blows air like I'm in the Gobi desert. Any ideas?
2) When I have either Heat or Defrost on my jeeps temp slowly drops down to around 160 on the gauge. Isn't that kinda bad? I believe it's the correct temp because when I turn off heat or defrost it slowly rises back up. Do I have a XJ that has a cooling problem rather than an overheating problem?
3) and lastely my tachometer won't read until I rev the engine up to 1500. Not really a big deal I can hear the engine so I know where it's revving but still. Is it mechanical or electrical? Possibly the low temperature is affecting the grease in the cable if its mechanical?

Sorry for three questions in one bit like I said all three manifested today and todays the first day I needed to put on jacket due to the cold. Any help is appreciated. Ask any questions you need to.

 

Well I realized no one answered me but here it goes

1) I get heat blowing out of every vent when I put it on Vent. So even if Heat doesn't do anything at least Vent does. If that's how's its supposed to work then I guess I'm just a fool but oh well.

2) Found out my electric fans (I have 4 fans on my rad) were constantly blowing at full speed. Turns out my wiring was faulty. So I'm guessing the drop in temperature is just due to the cold air outside being blown across the rad at full speed while the engine was idling, that plus using engine heat to blow in the cab was just taking more heat out of the engine then I expected. Hence the low reading on the gauge.

3) No idea on the tachometer yet but since it starts to read just from tapping the gas it's not really an issue.

Might help someone might not. But I'm happy with the findings.

 

I'll take a stab at why I think your temp drops. I think it may drop a little because when you turn it to heat it allows the coolant to circulate through the heater core. That will drop the temp a little.
I am really not sure what the other concerns you have with the vents. if you only are getting heat even when you adjust the controller to cool. your blend door is messed up. 94" right? my son's 95 the cable that moves the blend door was stripped and wasn't moving the lever that adjusts the door.
If your just not getting the flow to adjust from Heat-vent-defrost you have a vacuum issue. (track your lines from the little ball in your bumper thru the engine bay and see if they are in good shape). My 94 did not have the ball the PO removed it and mine was stuck on defrost. I got one from the SY and installed it and now I have it working again.
Just re read your post and yes if your electric fan runs none stop your temp will be about 160. I have an issue with my XJ were the fan never came on when the temp got to 220. I decided to just wire it in with a switch so I could make sure it came on when I needed it. I flip it on when ever I run steep grades for a long time or if when I am wheeling in extreme temps and it will drop right to 160.

 

You're losing vacuum to the heating system.

 

And I believe you're right. I've had a hose hanging there for awhile with a bolt jammed in it. And no reservoir there.
I knew the PO ran into a tree, I guess it busted open and he never replaced it.
Thank you very much.

 

You're welcome.