Heater Diagnosis Anyone?

[JRuffingRuff@xxxxxxx]

Hi,

Sounds like a possible thermostat.  When the vehicle warms up in the 
driveway, the air going through the radiator is less than that on the highway 
and the coolant flow is lesser also, and the vehicle can make heat even with 
a slightly defective (open, or opens too soon) thermostat.  Driving the car 
then cools the coolant down to the point where there isn't nice toasty heat.  
I replace many thermostats for symptoms similar to what you have described.  
This assumes that the basics have all been checked,  you have confirmed the 
coolant level, correct?  

Jeff Ruffing
65 Imperial Crown convert
ASE Master Technician