99 4.0S A/C blows cold only when it wants to. Just started checking things out. The outdoor temp. sensor seems to be working fine. The cabin temp sensor, well no way to really verify it but the air over assist fan in the sensor is running. Haven’t verified the solar gain or heater matrix sensors yet (still waiting on the service manual). Here’s what I have discovered. The floor, fascia and windshield program buttons work correctly however the floor/fascia and floor windshield program buttons are working backwards. i.e. the floor always gets air but the windshield position comes out of the fascia and the fascia position sends air to the windshield. Confused? It is. Any body have experience with the control system on this? Thanks in advance!

 

OH Ya , I've seen plenty.and I hate to tell ya this but there is no way you'll figure it out without the help of a Test Book. your climate control head shows an open book at the RS indicating a fault. this system was built to keep the dealers service dept buisy.and it usually gets expensive.
Several sensors can be at fault, coolant sensor, evaporator,condenser etc. and most cars with vent direction problems have multiple issues.

 

The book is not on the display. Everything seems to be working fine (with the possible exception of the A/C compressor running only when it wants to) except the air flow being switched between the fascia and the windshield when in blend mode.

 

If the compressor only cycles or runs intermitently and the book mark is not on. just check for a proper freon charge. A yellow sticker under the hood has the correct amount for your car, have your mechanic evacuate and recharge with the correct amount and see if that helps

 

Have you cleaned the two pollen filters for the blower motors? This is only a concern if you are NOT recirculating the interior air. One of my blower motors stopped working on my 99 4.0 and my pollen filters hadn't ever been changed or cleaned.

 

Yes I changed soon after getting the Rover. They were very, very dirty. But I really didn't notice a big differance in air flow.