Sound like your a/c compressor is putting too much load on the motor. Not sure on your ranger, but when the defrost is turn on, it will kick the a/c on also. The sure way to tell is to see if the motor bogs down when the a/c is on and try to change the heater to the floor mode without the a/c on and see if there is any change on the rpm.

Answered by jay4cars1
2 questions asked

tryed heat on floor and defrost does same thang.

Response from clayton dyer
4 questions asked

SNATCH THE WIRE OFF OF YOUR A/C COMPRESSOR (VEHICLE OFF)

SEE WHAT HAPPENS

THE MEDIC

Answered by CJ MEDEVAC (expert)
6,803 answers provided