Heat blows cold in 2004 Ford Explorer
Has 4.0L, V6 engine. When air comfort controls are set to heat it blows cool/cold air forcefully -- always when idling and sometimes when driving. When the engine is working hard while driving, it blows warm/hot with some frequency, but going downhill or when less power demands are on the engine, air goes tepid to slightly cool with settings still on heat. Has brand new thermostat, plenty of anti-freeze/fluid, new sealed radiator that is only about a year old, no clicking sound from cold to hot control. Sometimes when driving we hear a sound like the gurgling or slurping of fluid -- sounds like it may be from the engine area, but not certain of this. No engine overheating occurs and upon inspection the engine temp seems fine. Nothing is boiling over from the fluid reservoir or anywhere else. I appreciate any suggestions.
You could have a partially clogged heater core. Also, the heater control valve under the hood may not be opening completely. It is located on the left side of the engine compartment when facing the driver's compartment from the front. Trace the lines coming from the firewall and you will see it. It has a vacuum line attached to it. It could also be a problem with the blend door actuator not opening the blend door to allow head in (probable).
I had the same issue with no heat. Before you take apart your dash, open the hood and on the passenger side attached to one of the heater lines,there is a plastic valve with a vacuum on it. My valve was jammed in the closed position. The cost was $18.90 at the auto parts store. Ford wanted $50,00..screw ford. It takes not even 15 minutes to change. If you want to test it, remove both hoses attached to it and look in the valve. If you can't see through, try moving the valve by hand. It should feel like a t is spring loaded. If it's stuck, try forcing it till it opens. If it's jammed you will need a new one. You could probably un jam it and leave it open and you,lol have heat. Personally I would replace it for $18.00 because replacing it at 75 degrees outside is nicer than -10 don't you agree.
I have a 1986 lincoln with the air conditioner on runs fine when it is at a idle when I drive down the road given it gas it switches to heat. When I take my foot off the accelerator it goes back to cold
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