Last year my a/c started blowing very hot air, like the heater was on constantly. I took the car to the Merc dealer and without diagnostics being done was told a shaft attached to a motor under the dash was broken causing this. However a day later the A/C started working again and has done so gor over a year.


Now the problems back. All functions work except that hot air from the heater exits all ports. The a/c compressor, condensor and evaporatorseem to be working fine but I get nothing but hot air from the heater.


Any suggestions?

Could be the heater control valve. It's in the engine compartment, on the firewall, passenger side, were the big coolant hose comes out.


Haven't worked on it myself (yet), so I can't tell you anything further.


Only that I took it out on another car (not Mercury brand), cleaned it with brake cleaner/degreeser, instantly washed it out (cause brake cleaner is agressive on certain materials) and reinstalled.


It did the trick!