Yesterday my heater worked fine on the Covered Bridge Tour; today after doing a routine coolant change (not a flush - just a drain and fill), I get no heat from the system....AC works fine, fan works fine and the selector switch for the vent positions works fine. I have turned the temp knob CW and CCW several times - still no heat. Is there a possibility that while draining the coolant, some coolant also drained from the heater core and, even with the short test drive I took after the refill, the coolant hasn't circulated in the core to drive out an air bubble??? I checked fuses....there doesn't seem to be a specific fuse for heater operation....I don't have an electrical diagram....is there a relay in the system specifically for temp control? If so, would someone which relay it is?
Thanks,
Chip Krout
2007 MX5