mdj14

Just purchased a 98 step side with a 4.2 and manual transmission. I knew the ac was not blowing cold, but I just realized on a cold morning that the heat does not blow hot. The fan works, the two hoses running to the heater core are warm to hot. The coolant reservoir was low and very dirty when I bought it. I have topped off the coolant. Any direction or diagnostic advice would be greatly appreciated.

R&TBabich

Can you change the heat control from defrost to vents?
All vehicles have the fail mode where the heat will go to defrost the windshield.
If you have a vacuum controlled vent door and the vent door vacuum actuator is not working the heat will be directed to the windshield.
Do you have a heater cutoff valve in one hose to the heater core?
The valve may be stuck shut.
The valve is normally open in heat mode and stops coolant flow to the heater core in AC mode.

mdj14

Thanks for the direction. I'll try and check that tomorrow. I topped off the coolant again. It is not leaving a puddle on the ground and the engine runs great. I'm a little perplexed. Maybe there was air in the coolant creating a blockage. When I first topped it off there was a decent amount of heat coming out of the panel vents.