00_WJ_4.0

So I recently bought another grand, a 99. When I turn the heat on, no matter the setting, it only comes out of the defroster. As far as I can tell, all my vaccume lines are still connected, ( three were off on the intake when I got it, I've since hooked them up again) and the switch feels like it's clicking from place to place. Anybody have any ideas?

dave1123

The defroster is the default setting. Have you checked for vacuum actually getting to the switch? Does your cruise control work?

00_WJ_4.0

I haven't checked the cruise yet because it isn't on the road and I haven't pulled the dash apart to see about vaccum at the switch. Guess that's a good place to start when I can actually get to the jeep again.

dave1123

I don't know your history with jeeps so I'm going to run thru the vacuum circuit that supplies the heater and cruise control. There's a hose that comes off the top rear of the intake manifold and runs across the engine compartment near the firewall. There's a "T" fitting above the heater that goes thru the firewall to the heater, the hose continues to the cruise control vacuum motor on the fender and "T"s there again. That hose continues under the battery to the accumulator mounted in front of the fan relay under the headlight. Vacuum is a funny thing because a leak anywhere will cause it to stop functioning. The accumulator is a thin plastic box that's easily damaged, especially with a good bumper hit.

After the hose comes thru the firewall, there is supposed to be a check valve in it so the heater doors will close off after the engine shuts off. I've been told the 99s and some of the 2000s didn't have that check valve. IDK why it would be THERE anyhow because it needs the accumulator for power to do what they say. It would be better off in the line from the manifold.

All bets are off if you have the automatic climate control however! That thing is an electronic nightmare with it's own computer!

00_WJ_4.0

I'm only somewhat familiar with them. Comically, in ownimg five WJ's in total, you'd think I'd know them well and to a point I do but I've never had any odd ball issues like this with any of them. Did see a video on YouTube about it but his was a simple fix, the line on the intake, I knew about the one under the battery due to that video but that's where my knowledge ends on that subject.

00_WJ_4.0

It IS in fact just the regular system that all my other jeeps have had though. And I've had them with a wide range of options, from a pretty much fully loaded 00 v8 loaded with bells and whistles, to my current 99 that's as basic as they can get, including the lack of a skim ignition system. Plain old black key for that one.