Awesome, thank you. I can always count on you subford, and you even put schematics and pictures in the post to help out a Marine!! will check it out!!

Semper Fi

Hey folks, Long time no chat.
I have an issue with the front heating/AC system again on the RV. Sometimes it works fine and sometimes nothing! I have changed the fan speed controller for I heard that part can be an issue for drawing too much juice and melts. Anyway I can be driving down the road and put it on high, switching between AC, MAX AC, Vent and nothing. Then I will come to a stoplight and it starts blowing. What the.... Sounds like a loose wire to me but where? Thanks for any insight, it is driving me nuts

Semper Fi

Are you sure when you say it is not blowing that it may be blowing out the defrost vent and is switching to the dash vents when you stop?

If so this is a common problem, this is caused most of the time with a broken vacuum line most likely going to the outside air vacuum motor.

Thanks for the reply Subford!
When I was messing with it yesterday I was switching between all possible combinations (Hi,low,AC,VEnt, etc) when stopped (before our little trip). I finally decided to go anyway for the kids were excited. When on the highway I would feel air coming from the vents (main dash) but I figured it is just from the vehicle movement since it was on off. I kept messing with it at a stop light and all of a sudden it started to blow hard on high, then low and worked fine to whatever combination I would set it to. The AC probably needs some charging as it was not getting super cold. Of course it was only 50 outside.

Thank you

Semper Fi

Sounds like a bad connection in the wiring plugs someplace.
Did you change the relay or just the function control?

http://i54.photobucket.com/albums/g9...psf20b3741.jpg

http://i54.photobucket.com/albums/g9...ps856f27e9.jpg

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This definitely sounds more like the Function Control itself acting up. I've rarely seen one of them fail but certainly its not impossible.

The other possibility is an over heated blower connector to the dash switch or similar in the Function Control too.

Thanks guys. I changed the A/C blower control switch this past summer and the Relay a few years ago. After the relay was replaced back in 2011 it worked great. It just has been recently that it works intermittently, hence me changing out the switch. I also noted last night that the right turn arrow does not illuminate on the dash, but it does activate the turn signal..Arggg

Semper Fi

Have we ever replaced the blower motor resistor?

Hmmm, I do not believe I have ever changed the resistor. Let me check the Haynes manual and see where that bad boy resides. Thanks

Semper Fi

Even with a bad burned up resister it will still run on hi speed.

I have to correct you on that one subford. I believe that to be a myth. Just fixed one of the vans, had a bad resistor, and it was stuck on low. I have done my own trucks twice and both times it did not work period. I typically check fuses first and then blower motor resistor.

Here is the location of the resistor USMC.
http://i11.photobucket.com/albums/a1...orLocation.jpg
Its down below that wire hookup. I find it easiest and best to remove the battery and battery tray to get full and easy access to the BMR.

Power does not even go to the resister when it is on HI.
Look at the diagram above.

Hmmm, so is this kind of what I should look for? HAYDEN ADJUSTABLE THERMOSTATIC FAN CONTROL KIT ? Is this what you are describing as "Function control"?

Semper Fi

I will take my 5 times of experience of that diagram being quite inaccurate. Lol. Not mention that that doesn't mean something didn't corrode apart in the resistor and is now touching a place it shouldn't and sending a signal.

This looks like an aftermarket radiator fan control, not the blower motor fan.

Have you tried just replacing the actual fan speed switch in the dash? I know I have done 3 or 4 before.

The diagram is accurate. All of the Fords I have worked on for 40 years have work the way the diagram says.
You send power to the fan motor and the speed is regulated by the other fans wire to ground. Hi speed bypasses the resisters to ground.