All of the sudden i have no heat in the car

The dash thermo shows that the engine is getting up to temp - no heat out of the vents - run the dial all of hte way up to "red"

What is the best way to troubleshoot?

Thermostat? heater core plugged? where do I go first?

JPJM

 

check and see if you have coolant in your reservoir. if you dont there is the source of the lock of heat.

 

yes - coolant in the res

Where next?

 

so the guage goes all the way to the hot side?

 

Does your dash have the mixer vent control like the S70's? If so, close it.

Next, there is a chance that the controller that opens up the heat side of the duct work is broken or the arm for it is broken. It happens a lot with the older cars. My guess is that the controller is broken. It sure how to get at it in the S40, but in the S70 you pull the glove box.