[Black994x4]

A little history before getting to my problem.

The jeep is a 1999 WJ w/ ATC. I did the following repairs in late August:

- New updated blend doors (to fix the no heat on passenger side)
- New recirculate door (recommended to do while I had it broken down)

Everything functions great - I have heat when I want it and cold when I want it, and everything comes from the correct vents (defrost, dash, floor, etc).....unitl....

There is high humidity - that is when the issues start. Twice in the past month, once when it was blazing hot outside and once when it was cold outside. (I have seen a few 70 degree swings in 12 hrs recently)

When it was hot and humid outside - I had no control over where the air blew (i.e. mode door functions) and I had zero control over the temperature of the air (it was hot, i.e. blend door functions). The blower worked, and regulated the speed. Everything was blowing out of the defrost vents this time and it was hot on both the driver and passenger side. Made my uncomfortable ride home and the next day everything worked perfectly...For a little over a month.

A few nights ago, it was very cold outside but 100% humidity. I needed the defroster to get rid of the steam and frost on the windows - but I could not get heat and everything was blowing out of the floor - all cold. No matter what mode I selected, it was coming out the floor and no matter what temp. I selected it was cold on both sides. Cussed during my 15 minute drive home and whet out the next day, and everything works great - I got heat where I wanted and cool where I wanted. I pulled the codes the night it was not working and this is what I got:

42
45
46
47
48
53
54
56

Once I was done, I cleared them.

Have been driving for around a week w/ no issues.

I went out this morning, and everything functions perfectly. I pulled the codes for the fun of it, and here is what I got:

0

Since this is so intermittent and ONLY happens when the humidity is high, and effects blend and mode functions, doesn't it sound like the Dash Control Unit? Any way to test that unit to see if it is going out? Other thoughts?

[WJeff]

Same thing happened after I replaced blend doors - every code in the book - heat on one side, AC on the other. Other times it worked perfectly. I replaced dash controls with junkyard unit and it's been fine ever since. 15 minute job to replace.

Good Luck

[Black994x4]

I will try a different one and see if that works.

[VulcanJeep]

If you're good with a soldering iron, pull the back cover off the temperature control unit, and using a magnifier, look for cracked connections on the board, especially where the temperature and mode switches mount to the board. That might explain the intermittent nature of your problem.