chudson12787

i recently picked up a 97 f150 4x4 4.6 motor auto trans it has multiple minor issues but first on my list is the heater doesnt work. i know its the middle of the summer but in the rain with the windows up in the rain the windshield fogs up so i gotta fix it. when i switch the heat on it just blows cold air as if the air was on there is no coolant in the floor also sometimes the ac works fine and sometimes it blows a fog out of the vent on theright side of the steering wheel. anyone have any ideas

udderbrudder

First thing to check would be the vacuum supply to the heater control. The vacuum hose that feeds it is behind the battery. Check to see if it's broken (it's plastic). If so you can splice it. If it doesn't appear broken, you'll need to remove the heater control to verify that it's getting vacuum. If it is, check for vacuum at the vent control motor and blend door motor under the dash.

DavidSalsbury5150

Your heater core may be clogged. Disconnect the inlet and outlet hose's going into and out of the heater core at the firewall. They'll be in the passenger side of the engine compartment. Take a garden hose with low pressure and flush out the core. If that don't work, it may be the little flap inside the dash that that switches from hot to cool air is broken. The good news is that the part is kinda cheap, under a $100, but the bad news is that the labor cost is through the roof. It's something like 10 hours of labor to get to the heater core and the lil flap. The entire dash has to come out to get to it. If that's what you have to do, replace the heater core while its all apart.