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95 Ford Explorer blowing cold air - Not thermostat or air in the system

Thermostat is new and in correctly.

It looks like fluid is moving through heater core so I don’t think there is any air in the system.

Is there something that opens or allows the air to move over the heater core that could be stuck or not working?

On occasion it works for a few minutes and there is a subtle sound difference when it does and then it stops working.

Thoughts, Ideas, Suggestions? Thanks for any and all input.

It’s called a “Blend Door.” It is the device that changes when you increase or decrease the heat setting*. Some are cable controlled using a wire and others are vacuum controlled. I don’t know which yours has. If it is a vacuum control (more likely) then you could have a vacuum leak almost anywhere in the vacuum or the vacuum motor at the heater is out.

How are your brakes? They also use the vacuum and with a system wide vacuum problem you will likely have the power brakes acting up and requiring more than usual force. If not then it likely is under the dash with a loose or cracked vacuum hose. You might even get a short burst of heat when you let up on the accelerator.

If it is a wire controlled system, then you need to get in there and find out what has happened. The wire may have come loose at one end or the other.

  • Some new cars are using a electric system but I doubt that a 1995 would have that.

I agree. It’s probably the blend door, which controls air temperature by diverting incoming air through the heater core or the AC evaporator, or both, depending on the desired temperature.

If the coolant hoses leading to and from the heater core are both when the engine is warmed up, then you have flow through the core and the problem is under the dash.

The blend air door on this car is electrically controlled, not vacuum or cable. That applies to both manual and auto climate control. If you’re very lucky, it’s the motor assembly which is not too difficult to change out. If your case is like most of these, then the blend air door itself must come out, and that is a major job.

All of the air always passes through the AC evaporator. The blend air door determines if the air passes through the heater core too, or bypasses it.