Heater Frustrations
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New User
Joined: Oct 2010
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From: Alberta, Canada
Heater Frustrations
The truck is a 1999 F250 with a 5.4L Triton engine. Never has any heat. Both heater hoses @ firewall get hot. Undone heater hoses & water from a garden hose flows thru heater core well. Have vacuum to black hose behind heater controls. Controls seem to move ok. Checked related fuses under dash & under hood. Also swapped relays around. No wires seem to be off under dash. Any ideas would be helpful, thank you
Lead Driver
Joined: Sep 2007
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From: Scio, OR
I would suspect the blend door. It is controlled by an electric motor that is controlled by the warm/cool ****. I can't give you an exact location, but I have posted a general diagram below.
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From: Alberta, Canada
Yes, I was thinking that the problem with the heat was leading up to the blend door. I should have heat @ the heater core. If I had a laser shooting thermometer I could aim it @ the HVAC box. But I will first see if I have any power @ any time down to my actuator. Will try after I send the little man off to bed. Anyone know which wires down there are for what ?
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From: Alberta, Canada
Also, I was thinking that it is possible to have an air pocket trapped in the heater core area. I heard that if I whipped the hoses off then back on while running it may cure it. Of course its a messy process. Any tricks with this ?
Lead Driver
Joined: Sep 2007
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From: Scio, OR
I don't believe this is your problem. If it were, it would have to be preventing coolant flow through the heater core to be causing a problem, and if there wasn't coolant flow through the heater core, they're wouldn't be coolant flow through the hoses and they wouldn't get hot.
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heater proplems
why did you wait 11 years to address this problem.you should have flushed the system years ago.this is called preventive maintanence.flush it with a good good cooling system flush.followed by a distilled water flush.then distilled water and the proper 50/50 anti-freeze solution.
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Good tip about the coolant concentration percentages & so I had just bought this F250 about a month ago. The electrical breakdown is useful as with the engine running I only have power @ the #7 pin & ground @ #8 pin as noted. No power at any other pins no matter on the position of the temp dial or the vent selector position switch. Also... No power ever is @ either @ the 2 plugs that go to the back of the temp selector switch. Yet I have checked all pertinent fuses & swapped relays. The truck itself is in pristine condition. Anyway, still no heat...
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I am thinking that I need power to these other pins on the plug as shown. I only have wiring on my truck to pins 3,4, 6,7 &8. No terminals on others in plug. Might need electrical schematic to backtrace through wiring.
Lead Driver
Joined: Sep 2007
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From: Scio, OR
These are the diagrams. They aren't labeled but the one with the blend door actuator and temp control dial is 54-4. It references connection C (triangle with a C in it) in diagram 54-1, which is the other diagram.
It appears that pin 7 of the connector to the blend door actuator is powered by fuse 28 in the Central Junction Box. Pin 8 of the connector goes to ground. The fuse number may be different, fuses did change between model years. Mine is a 2004 and I don't think the same fuse panel went back as far as 1999. The fuse is labeled "EATC module/Front blower relay coil" in my owner's manual. But that may be different in yours as well.
Pins 3, 4 and 6 are wires back to the heater control, and it appears from the diagram that you won't see any power on those, just a change in resistance as you turn the heat control ****.
It appears that pin 7 of the connector to the blend door actuator is powered by fuse 28 in the Central Junction Box. Pin 8 of the connector goes to ground. The fuse number may be different, fuses did change between model years. Mine is a 2004 and I don't think the same fuse panel went back as far as 1999. The fuse is labeled "EATC module/Front blower relay coil" in my owner's manual. But that may be different in yours as well.
Pins 3, 4 and 6 are wires back to the heater control, and it appears from the diagram that you won't see any power on those, just a change in resistance as you turn the heat control ****.