I have seen plenty of threads about the heat and AC blowing only out of defrost but I just don't understand where to look or how to check.


I have a 96 xj and both the heat and air blow only out of the defrost. Plus my cruise control does not work. I read that they are the same tube but not 100% on it.

Can any of you expert xjers help me out.

 

Pics tell 1000 words.....

 

Yep, Freedgr is right. Really though we need a better diagram. Short story, the large line from the intake "charges" the ball, which has a check valve right in it. Then the small black tube comes back up to do the work.

Longer story...it seems it's divided in two, with two check valves, and two smaller tubes, likely one for the cruise and the other for the vacuum motor's in the heater controls. That's as far as I've gotten with it....In any case see if the lines are connected to it, (easier said then done), and see if you have vacuum from the small line coming back. On mine it's black, and goes into the firewall.

 

I have the same issue. Cruise doesn't work but ac blows out of the vents and heat only blows out of defrost. I just put it on vent and it blows out of the vents so it doesn't bother me

 

Open this link for pics of the engine bay vacuum system.

https://picasaweb.google.com/ken384/...eat=directlink

Click the image then look at the top menu bar (next to "Download") for a magnfying glass icon. Click it and the image will get bigger. On the left will be a +/- tool to zoom in.

These pics are for a '99 XJ. The '96 will be different but they give you an idea what to look for.

 

Only one line on renix no small lline ........

 

Schematic of the historical type XJ's showing the reservoir taps.

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If a/c blows out the vents, heat should blow out the vents as well when the selector slide/**** is moved/turned toward heat/red. Warm/hot air will blow out any vent position, even in the a/c position, when the temp slide/**** is moved to heat/red. The heat is way more powerful than the a/c and will "overide/overpower" the a/c.

 

Nice Ken! Do you happen to have one for the "historical" Cruse control's? My "new to me" 90 has a split bottle with a forest of lines. (that AC Diag. shows the in, out for the AC, and one "chamber/check valve.) My bottle has two check valves, and two lines on each end.

 

Can find anything on this by thumbing through the dead sea scrolls, but my best guess is that the reservoir is constructed in two seperate/isolated parts (split line shown), one half for the vehicle speed control vacuum circuit and the other half for the climate control vacuum circuit.

Edit: I did pinch your pic. :-)

 

Yea, that was my assumption as well. (they ARE separated, I checked). Pinch away!

 

One other thing besides the main vacuum leaks--on the back of the HVAC controls is a small vacuum manifold with all the colored hoses. Sometimes that will develop poor seal and allow leaks to specific diaphragms. I had to pull mine out, clean the manifold with alcohol and put a little silicone grease to improve the seal.

 

Looking at your photo, I take it that larger hose that is tee'd is the vacuum source from the intake. Can you ID where, in that pic, the two smaller plastic tubes go. One to the servo and the other to the HVAC climate control panel, but which is which?

 

NO! Gads, I was at wit's end. Swapping bumpers was the easy part. Fitting the end caps right and the little stuff had me "fumen". I'll try to let you know when I go back....one of my check valves is failed.

A side thought. If you are gassen it enough to need backup vacuum, you normally wouldn't be in cruse.

Assuming there was vacuum at both heat and cruse, I suppose I guy could disconnect one at the bottle, and know which is which.

Correct, it's "T'd" Course it only needs one source of vacuum from the intake to "charge" them. Then the little rigid "work" tubes go to separate functions, it seems.

Btw I was a little slow wrapping my head around some of this vacuum stuff. A small "apifony" for me was to realize, unless you have a bad diaphragm somewhere, or a line leak, or a problem like Ehall mentions (Thanks ehall!), Whew. Unless you have a leak it will hold vacuum for days. There is no flow, it's just like a push-rod, except it pulls.

 

Take a look at this pic and let me know if the titles and routings are correct.

I got this info from the parts catalog (which can't be trusted).