Folks,
I know there's been a lot of discussion about this before but I can't find a thread that exactly fits the symptoms on my Jeep (96 4.0 LTD, RHD).

When the heater lever is on any position apart from HEAT - it works fine. I get the right temp and decent airflow according to the fan speed. But on heat there's no airflow at all even if I turn the fan to max. On demist, there's loads of hot air hitting the windscreen so I know the matrix is good and the fan works.

I've seen people talking about the blend doors and that the vacuum might have failed - but the blend doors do seem to be moving because all the other modes work fine (I can get lots of cold air through the dash vents if needed).

Am I wrong? Is it likely to be vacuum related? What should I check first?
thanks!
Morat.

 

Definitely go to the passenger side of your front bumper and look underneath for the vacuum bottle that should be there. Make sure the vacuum line is hooked up to it and that it has no cracks or holes in it. Do that first. It's something you can do for free that might just fix your problem. Then, go from there with your troubleshooting.

 

I'd definitely look at the vacuum lines first. Not sure on the <'97, but on my '00 there is the cluster at the HVAC controls, three on the most passenger side of the HVAC box (this being in the US - left hand drive), one behind the radio area also on the HVAC box, and another that feeds through the firewall to a "T" fitting in the engine bay.

Hope this helps.

 

Or flush your heatercore...mine was packed FULL with crap

 

OK, I'll start looking for the vacuum lines tomorrow night before it gets dark. I'm pretty sure the matrix is OK, I flushed it yesterday when I replaced the heater control valve and the demist gets nice and hot.
I was hoping the heater control valve would also fix the heat issue, but no such luck.