I had to go out of town the other day and was towing my fifth wheel trailer behind me. When I left, the AC/Heater fan was working fine. Somewhere along the way, it simply quit. I didn't notice it until things started to heat up inside. All other electrical systems seem to be working fine.

I have a downloaded copy of what is supposed to be the Owner's Manual for this truck (2006 F350SD Crew Cab 6.0 Diesel Auto). The fuse chart there lists the number 24 fuse as being the one for the AC/Heater fan. I checked it with a test light and it was good. I checked all of the others and found them to be good also.

The fan doesn't work on any of the four speeds. Seems odd that the whole fan would go belly up without warning.

Any of you experienced hands have any other ideas for me to check out?

 

The fan went out on my 03 Suburban and it turned out to be a resistor (I think) behind the glove box that went bad. Maybe Ford has the same thing somewhere. I don't know for sure or maybe a relay somewhere.

Try this
http://www.fixya.com/cars/t8668688-2006_f250_blower

or this
https://www.ford-trucks.com/forums/7...-resistor.html

 

Thanks for the tip. I am familiar with the blower motor resistor from my days with an F150. In my experience with the blower motor resistor, one speed is all that usually fails. In my case, none of them are working. I will check out the resistor tomorrow and probably put a meter on it to see if I am even getting voltage there. Hopefully, it will be located under the hood and NOT in the heater box. That was a real pain in the a** on the F150. And, at my age, my body does not bend in the kinks necessary to easily get under the dash!

 

When my blower went out on my Suburban it would not work on any speed....

 

I am probably going to be tied up with other things today but will try to check out the resistor tomorrow. Will put a meter on it to see if I'm even getting voltage at the fan. Truck is new to me, but I believe on this model the fan and related wiring are mostly accessible from under the hood without needing to tear the dash and heater box apart. Hopefully, anyway. I'll post back after that test.

 

The fan has quit on my 04 F350 twice in 320,000kms and both times it was the resistor. One would think that only one speed would be lost but on my truck you loose all speeds when the resistor dies. At the dealer in Canada it is about a $200 repair - a little over $100 for the resistor and about an hour in labour.

 

The blower motor resistor also has a thermal cutoff switch in it. If it's going out repeatedly, I would check the amp draw of the fan motor. It may be going bad and starting to draw too many amps.

Another common problem is corrosion and otherwise bad connections in the fan motor connector. Look it over for signs of corrosion, burning or melting.

 

My fan stopped working on all settings but high......Any ideas there?????

 

Yup. Read above^

 

Have checked fuse No. 24 under the dash and No. 2 under the hood and both are good. Am not getting any voltage across the terminals at the fan motor. Have located the blower resistor next to the fan motor under the hood and can remove and replace it easily (O'Reilly auto parts has a Dorman for about $12).

Before I do that, "If I pull the pigtail connected to the resistor, which pin(s) would I need to check for proper voltage GOING INTO the resistor?" I'd like to be sure the problem is not further back before I start randomly replacing parts. At this time, I don't have access to a wiring diagram that will tell me this.

If anyone can help, it would be greatly appreciated.

 

This is the wiring and connector diagrams from the service manual. I have to say, though, they never made much sense to me, since as near as I can tell the blower has 4 speeds and this diagram only shows 3.

 

Thank you so much. This should help me tremendously.

Without going through it tonight, I'm going to assume that the reason you are only seeing three connections is because the 'high speed' is a 'non-resistance' pass through.

I'll let you know how this works out. If I can't figure out something from this, I'll probably just spring for the $12 resistor and see what happens.

Thanks again for all your help.

 

David


If you look at the right hand portion of the lower diagram, you can see that when the fan is turned to high (position 10 in the diagram), it is bypassing the resistor assembly completely and providing straight through voltage to the fan motor as I suspected. There are three resistors in the resistor assembly. Using one, two, or three resistors in series provides the lower three fan speeds by altering the ground connection to the blower motor.

It appears that I need to check the BN/OG (Brown/Orange) wire coming from the Blower Motor Relay first. If I don't have power there, will need to work further back.

 

Yeah I think I figured that out. The thing I wasn't getting is that they only show 3 switch positions. I'm figuring there is a 4th position that isn't connected to anything. That would let the current flow through all 3 resistors and out to ground through pin 2 of the resistor connector. That would be the lowest speed.

But yeah, there should be power to pin 4, assuming the main switch is on to energize the blower motor relay coil.

 

If you look at the diagram you provided where it shows the switch, you'll see a line to the right that goes to the third resistor but is not shown connected to the switch. I'm suspecting that there might be a three speed and a four speed switch option and they only detailed the three speed. Basic info is all there though with a little intuition.

Am going to try to check a couple more wires today to see if I can isolate my problem.