1989 Dodge Dakota 3.9 2WD. The A/C blows nice and cold (48) on all fan speeds except HIGH (the clutch turns off). Once I lower the fan speed, the clutch kicks back on and everything is cool again!

Blower resistor

I thought a bad resistor only allowed the fan to blow at one speed.

Correct and that speed is

wait for it

High

And it doesn't effect the clutch, unless the AC line pressure gets too high, but that would the the pressure switch kicking in.

Still don't understand what the blower speed has to do with the clutch! What am I missing?

I'm thinking the line pressure

So the high blower speed causes increased line pressure that activates the clutch cutoff?? Do I have that right? I mean a resistor is dirt cheap, I just want to understand it too!

Lack of the fan working might be causing the line pressure to rise triggering the high pressure shut off, but it would not be instantaneous.

You probably have a short dropping power to the clutch circuit when you switch to high fan speed. Unplug the fan and see what happens when you put it in high.

**************It seems it was the blower resistor************************* Thanks

glad it was a simple fix !