I was driving at 45 mph and I put the heater on and the engin started to surge like it was loosing ground connection. I turned the heater off and it went away. I was driving up a slight hill so the engin was under some load. 96 xj 4.0 auto I needed to get home so I didnt try other heater selections. I was not using the defroster.
any one know what this might be?
the check engin light came on and I connected a obd2 scanner and it would not finnish linking to my jeep.
I figured the scanner was broken.

 

I had that. Every time the heater came on, the engine would surge and the lights would dim. Replaced the heater core and it went away.

 

really? that seems to not make sense to me. If Im wrong Im not trying to flame just I need more explanaiton to convince me.

 

I don't really understand it either. My guess is that there was an electrical fault somewhere in the blower wiring, and after I pulled all that stuff to replace the heater core, I accidentally fixed the problem putting it all back in.