TennRay

I am a new forum member although I have visited F150 Forum many times in the past. Now I need help. It is 92 degrees and my a/c blower fan will not come on, with the switch. 2 weeks ago I was out doing errands and I got out of my truck to go in a store. The air was on and running well. My air is very, very cold. When I started the truck back up, no fan. The a/c was on and cycling and as long as I was moving I had cold air. I figured easy, the fuse blew. No such luck. The fuse was fine. I replaced it anyway. Over the next couple of days I replaced the switch and the resistor even though bench testing showed them to be fine. The fan will run with direct 12 volts applied. I tested the plug at the fan motor and have 11.84 volts on the brown/violet wire. The plug connectors are tight and corrosion free. As soon as I plug in the motor and push a meter probe into the back side of the switch the voltage drops to micro volts. It seems that I have 12 volts until a load is placed on the circuit. I did a jumper wire for the ground and no luck there either. I really hate to have to use an electrical shop. What's going on?

Chris_1

iTrader: (1)

Maybe the connection at the resistor pack is bad ?

TennRay

The connection at the resistor is nice and tight. I did some more checking and I found that by using jumper wires at the motor connector I get 11.84 volts coming in from the fuse panel. I get the same coming out of the motor to the resistor(orange/black). I unplugged the connector at the resistor and I get the same. When I plug the connector in the voltage drops to micro-volts. There is something that puzzles me. I can direct jump the blower motor to the battery and it runs. If I use the power out of the blower connector(br/v) and use ground from the battery it will not run. Why?