I have a very strange thing happening to the HVAC system.
When I disconnect the battery and leave key in the on position
when I reconnect batterry the HVAC system will blow air with no
fault showing on the dysplay for a couple mins. But as soon as
turn the engine off and turn it back on again, the system stops working!!!
I Checked the fuses and the dreaded RL7 which upon close inspection
showed signs of extreme discoloration the fuse box contact also
showed cracks and stress from the heat. So after some research on the boards
I decided to replace the RL7 first with no luck. Then I purchased a used
fuse box that showed no signs of heat damage on the board and
after swaping it tonight I still get the same behavior as I described above!!!!
Any sugestions on what to do next?
Did anyone have a similar problem and can share a solution.
Thanks for your help.
Ricardo Oliveira
1997 4.0 se P38

 

It is probably your climate control ecu going out. Make sure that is what it is they can be pretty pricey.

 

Scott,
thanks for the reply!
I was afraid you were going to suggest blend motors
btw based on my fault description, is there any indication
of being blend motor problem as well?
Thanks!
Ricardo.
1997 4.0 SE

 

Well if the entire system stops working, I doubt its your blend motors. They usually cause temperature variances between the two climate zones (in correct temp variances, such as one side cold one side hot), and can cause recirc not to work properly either. When a blend motor fails or is about to, it almost always illuminates the check book symbol. I know cause I think a couple of mine are failing .

 

When you say the system stops working what exactly do you mean? You have no air circulating, it's not cool air, etc. What exactly are the symptoms?

 

Scott,
Many thanks for the information on why you don't think
it's a blend motor problem.
I'll try the climate control ecu route and keep you guys posted

Ricardo Oliveira
1997 4.0 SE

 

I accept with information:If its backfire thru the carb its usually on the intake side, valves, pushrod,tight or lose valve adjust. Pull the valve covers and look better than a guess.