I noticed last week that my heat was pulsing in my Dodge. It was slight and it seemed to be when engine RPM's were down it would get cold. So I was thinking maybe the vac diverter was messed up. Well today I noticed that the engine temp gauge is also pulsing. It got real bad this morning. The gauge would go from 1/4 - 3/4... back and forth in intervals. When it was on the cold side I had no heat... when it was on the hot side I'd have super hot heat.

The gauge usually runs a hair under half. I'm thinking it's the thermostat???

Opinions? [/align][/align]

 

could be the heater core....

 

but would a heater core make the temp gauge go up and down?

 

if its restricting flow... it would allow the temperature to fluctuate sure.. just like a thermostat...