Expert: Paul Evans/ www.chillywillys.org - 3/15/2011

Question
Hi  Paul,

Two questions;

In my 2005 Caravan when I turn on my A/C the engine temperature guage goes way up.

1.  What would cause that ?

My interior heater fan control doesn't work.

2.  Any hints how to fix that, I checked the fuse box, no luck.

Thanks,
AL

Answer
Hi Al

We have the same vehicle except mine is a Chrysler
Assuming you have climate control, lets deal with the interior fan first;
If I understand you correctly when you turn the fan control on the left hand side of the heater control panel there is no action from the fan at all.
If this is correct, does it do the same thing when you ask for auto low /auto high ?
If you have no front interior fan at all the a/c compressor should not engage unless you ask for Rear/Auto. Does rear work and do you have an audible fan at the back ?

In normal vehicles (we don't have one of those) there is a resistor that controls the fan speed.
On full speed it bypasses the resistor and goes straight to relay / 12 volts.
If it works on full speed and no other I would be checking out the resistor located around the fan box in the passenger footwell behind the glove box and probably behind pretty much everything else too !
If it doesn't work at all I would suspect the fan motor under normal circumstances assuming that everything else works on the panel.

As for the temperature gauge, I am only guessing but this may help, is the engine as hot as the temperature gauge indicates, if so your engine fans will be running flat out.
If they are not running at all and the a/c compressor is engaged this will generate surplus heat in front of the radiator through the condenser, this will cause the engine temperature to rise.

Try all this first and let me know, it could be that a little time on the main dealer diagnostic would be money well spent if the fault is still not making any sense
I can understand that you would rather avoid doing that............if your dealer prices are anything like those of California.