ok so my obs heater is the issue. OK i have replaced blower motor, blower resistor, heater core, and i checked every thing i know to check.the blend door is working right from cold to warm. heater core hoses are getting hot. about the only thing that i have found is when the heat is on it pulls fresh air from outside and the only time it pulls from in the cab is when the a/c is on. i don't know if this normal for these trucks or not .i just don't know what else to do. when you turn it on it barely blows any air out at all and i know that isn't normal for a ford. i have had this truck for 4 years and its never had heat or a/c but i cant do the no heater thing again this winter. is there something i'm missing? all my ford trucks that i've had would burn you up when the truck got warm. this one is throwing me for a loop. any help would be appreciated.
camo4x4
when you change from AC, to floor, to vent etc can you hear the vacuum activated switching of the routing of the air? You could possibly have it stuck in between so that the air is going in all directions
have you checked the heater core for blockage on coolant and air. check to make sure the core is not air locked. are you low on coolant.
We had a superduty truck come in at work with a similar problem, owner complained of minimal air flow even with the blower on hi speed. Here's a pic of his a/c evaporator, his heater core looked just as bad:
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Is the blend door shutting completely? Have someone actually look at the actuator when switching to make sure it's working properly. I'm sure you know it's located on the air box above the blower motor. Mine turned out to be the blend door. Wasn't closing all the way. Almost, but not completely. That little 1/2" gap made all the difference.
Ok, so you hear all the blower speeds? and its not moving enough air?? if so try reversing the polarity on the blower motor, I have seen the blower motors rotating in the wrong direction (backwards) you will hear every speed, the blend door will all work like they should, but it won't move much air. I have seen a truck that had a problem from brand new and replace blower motors wired backwards, all you have to do is cross the wires. I have even seen blowers on house furances wired backwards.
The truck has coolant. Now the other day I did pull the glove boxs out and checked the blend door and the heater core. The blend door is opening and shutting as it should and the heater core is getting hot like it should. Last summer I replaced the whole dash and when I had it apart I ckecked for something blocking the vents and nothing. I know on other trucks I have worked on the heat the a/c had to work before the heat would cause the a/c dryer the air. but sure about the obs trucks. Now on my truck the a/c isn't hooked up. Could this be my issue from the get go? Is the a easy way to check the a/c evaporator with out pull half the heater boxs off. I work on big rigs and there HVAC systems aren't the same but close. And I have checked all that I know to check.
I *think* the airflow always flows past the A/C evaporator, so that would be the next thing to check (see bracketracer's pic above).
The air has to pass through the a/c evaporator on it's way either thru or around the heater core (depending on blend door position). So if the evap is cruddy, you don't get much airflow regardless of blend door position. May not be the op's problem but it's one more thing he can check out.
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