Whn air is on, cold air only comes thru window defroster
when running air condition, cold air only come out thru the window defroster area, air will
not come out of vents, and the amount of air coming thru the window defroster is not very
Does this only happen with the A/C or in all modes?
Sounds like the system has lost vacuum. Check for a broken or disconnected vacuum hose coming out of the firewall in the engine compartment. Then look around the top of the engine to find where it needs to be hooked up. HTH. -Jim
On a Ford the defrost mode is default, so if you loose vacuum it will go to defrost. The most common loss is a broken vacuum supply line from the engine, then the control valve leaking so it can't send vacuum to the vacuum motor that controls the mode door of the one selected. So that is the place to start.
Heater core or blower motor. Check to see if the fan on the radiator is cutting in and out, check antifreeze up to level and check to see if the air conditioner is running. Sometimes when switching the heat the buttons stick. Clean thoroughly! You tube has video to show what to do. See service if none of these things help. No thermostat can cause this. Some people remove the thermostats for whatever reasons thinking it will run like the older carburetor models this can harm the vehicle. Troubleshoot with manual suggestions found at the front of the Hanes manual for each year of vehicle.
All the vacuum hoses are connected. Still air only comes thru the defrost. What's next.
So next start checking the mode switch, see if it is supplying vacuum to each servo motor that you select by turning the knob, then check to make sure that the servo motors are responding to the supplied vacuum, so if the mode switch is not sending vacuum then it needs replaced, if it is sending vacuum and one or more servos don't respond then those need replaced.
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