I need help,my truck keeps blowing the heater fuse. I blew the 3rd one today I dont know whats causing it any ideas, tis a 76 f-250.

 

Does it blow the fuse on any fan setting? Could be your fan resistor. Something within the fan motor circuit is allowing it to draw to many amps. I'll check my wiring diagram and see if I can come up with more info.

 

I dont even turn the heater on and it blows em, I used the 30amp fuse like the manual says but it blows them one after another,when the battery is hooked up and u turn the key I dont know whats happening ,Ive traced all the wires and they are fine.its confusing to me.

 

Before you put in another fuse, unplug the wiring at the back of the heater fan switch and also at the resistor. This will eliminate those components & leave you tracing/checking the actual wires more closely.
AL.

 

Well I found the problem it had a wire connected in the wrong plug at the back of the blower switch I looked in my truck manual, but now im stuck with another question there are 2 plugs left unused and im not sure where they go, one is a thick brown wire with a male plug and the other is 2 wires red/blk stripes going into a single female plug where do these wires go? I looked in my manual but it doesnt show.My truck has the a/c-heater controls, with dual tanks, its all plugged in right ,but just those 2 plugs are left.

 

here is a pic not a good one, but the big black plug ,plugs into the ac compressor clutch switch on the bottom of the heater/ac controls the other 2 plugs im clueless.

 

Are these wires under the dash or in the engine compartment. I have a manual with wiring diagram and a 77, 78, 79 I can look at to try and determine what it might plug into. Do either of the 2 wires have voltage readings. If so you may want and hook a volt meter to them and start pulling fuses and see what fused circuit it is on. That may help figure out what they are for.

 

I havent checked the voltage yet, they are under the dash right behind the a/c-heater controls.See the main harness has a connector goes to the blower fan switch and the switch has a thick orange wire coming off of it with a male plug and it plugs in to the thick orange wire female plug coming from the heater side, fuse box.The harness in the pic,comes from under the passenger area where the blower motor and all is, and comes up behind the ac/heater controls ,the connectors shown are the big black one goes to the ac compressor clutch switch ,but the other 2 im clueless.One is the brown wire male plug the other 2 red wires/blk stripe,going into a female plug.I thought maybe they plug in to togther?I know they have to do with the a/c.The brown wire with male plug is coming off the plug for the a/c compressor clutch switch .The 2 red wires/blk stripes,go back over to the under the passenger area where the blower motor and all are and go into 2 plugs,one of which goes to a relay, or resistor under the passenger area.

 

I'll try and check out my trucks tomorow and see if I can identify them. I don't have a/c but it may give me a better idea were to look in the manual. I'll let you know.

 

My trucks do not have either of the wires you described. I have looked in my wiring diagram and it does show wiring for a/c and heat controls. Do you have a wiring diagram? If not I could possibly try and e-mail it to you (heat and a/c portion) if you would like. I don't think I could explain the wiring diagram well enough to you that you could make any sense out of it. If you had it and could trace the wires in your truck compared to the diagram it might help you.

 

I got it fixed thanks though actually the brown wire with the male plug, plugged right inot the red wirews/blk stripe feamle plug and it worked fine, no more blown fuses.

 

That's great, glad to here it.