got a bug up my rear a few months ago to install a DD nav unit in my '88 Xj.
If you're familiar with the pre 96 dash layout, you know this is a pain --- to get it to fit, I had to remove the vent, move the HVAC controls down, and heavily modify the vents and the plumbing behind the unit. To boot, the standard "slider" hvac controls are so deep, they hit one of the vaccum actuated doors that switches from vents to defrost. So, I had to remove the door.. and had no vent A/C
.
which was fine, until I came across this link: How to replace early XJ AC control sliders with 97+ dials -
Forums -::- North American XJ Association
I didn't know this, but the '96 and '96 hvac controls have a mechanical blend door just like my '88, but have a knob layout, and are inches shorter... which would JUST clear the vent door.
So, after many, many hours with a soldering iron and comparing various factory service manuals (in the post above, john used colors from a '93 xj... colors on the '88 are all different, so had to convert a bit), and wrangling with the dash, and installing five relays in the glovebox, here's the outcome.... to be honest, I like the look of the sliders better, but I now have working heat and AC from defrost, floor, AND vents:
,
If you're thinking of doing this, feel free to pm me. Now that I've gone through it, it's nice having nav and hd radio and Pandora on a nice screen, but I probably wouldn't have done it if I knew how much work it was. John (the guy that figured out the wiring in the above post) really saved me hours and hours of time figuring out wire mappings and vacuum line mappings. And I still need to futz with it -- it sits a bit too high, but it is such a pain to line everything up just right to get it to fit.
.
anyway, let me know what you think.
If you're familiar with the pre 96 dash layout, you know this is a pain --- to get it to fit, I had to remove the vent, move the HVAC controls down, and heavily modify the vents and the plumbing behind the unit. To boot, the standard "slider" hvac controls are so deep, they hit one of the vaccum actuated doors that switches from vents to defrost. So, I had to remove the door.. and had no vent A/C
.
which was fine, until I came across this link: How to replace early XJ AC control sliders with 97+ dials -

I didn't know this, but the '96 and '96 hvac controls have a mechanical blend door just like my '88, but have a knob layout, and are inches shorter... which would JUST clear the vent door.
So, after many, many hours with a soldering iron and comparing various factory service manuals (in the post above, john used colors from a '93 xj... colors on the '88 are all different, so had to convert a bit), and wrangling with the dash, and installing five relays in the glovebox, here's the outcome.... to be honest, I like the look of the sliders better, but I now have working heat and AC from defrost, floor, AND vents:



,
If you're thinking of doing this, feel free to pm me. Now that I've gone through it, it's nice having nav and hd radio and Pandora on a nice screen, but I probably wouldn't have done it if I knew how much work it was. John (the guy that figured out the wiring in the above post) really saved me hours and hours of time figuring out wire mappings and vacuum line mappings. And I still need to futz with it -- it sits a bit too high, but it is such a pain to line everything up just right to get it to fit.
.
anyway, let me know what you think.