heater fan

I have a 1978 C J. The heater fan don't work using the dash switch. I have power on both sides of the fuse that says heater but nothing going to the switch. The blower motor is new and works when there is power applied to it. Could I have a bad connection at the main fuse block? Every thing did work the first part of the year, then quit working. Any help would be nice.
Thanks, Don

 

check the fan resistor its located in the heater housing.

 

I put a new blower in last year, but don't remember seeing any resistor, but I will take the housing apart when it gets warmer. Thanks

 

i think its on the inside below the glove box should have 3 wires going into it...access from under the dash no need to remove the housing.

 

Thee is a three prong plug-in on the out side of the box. The unit is on the inside of it. How can I check this with out taking the cover apart? Thanks.

 

with an ohm meter no positive on values though.

 

I will have to buy a ohm meter .Can not find the one I had . Bad part about moving. Any way I don't have any power going to the plug in. I take it something has to be at the plug in to get to the resistor. Correct?

 

yes i think somewhere there should be 12 volts. i recall one terminal having two wires if 12 volts is applied there the fan should be on high . you need to get power to the switch it sends it to the resistor.

 

Thanks . I right know I have to wait for some warmer weather. It is minus 17 below to day ( not including the wind chill factor ) and no heat in the garage. Next year will be different.

 

Isn't there two small screws at each end of the resistor board (through the duct metal) and the resistors are mounted on this fiber board. The board is then twisted sideways and fed back out through the rectangular hole.

 

I will take a better look at this when it gets warmer out side, if that ever happens. Thanks

 

So no more 35 below weather. I have power on both sides of the fuse but no power at the heater fan switch and nothing at the resistor. Should I take fuse block apart and see if the problem is there? Could I run a new wire to the switch, or is that asking for trouble? The blower motor works by running power to it from the battery. I take it the power goes to the switch then to the resistor, or am I wrong on that ?

 

you have power on both side of the fuse, but not at the switch? What about the side of the switch that goes to the fuse? you should have power there if both sides of the fuse have it. It sounds like a new switch is in order.

 

I must be missing something here. I pulled the switch from the plug in. I do not have any power at the plug in that goes on the switch. If the power is coming out of the fuse block I don't understand why nothing is going to the switch. I am getting a head ache. Maybe a bad wire some place? The heater fan was working but then it just stopped.
Thanks.

 

The tan wire from the fuse block should be hot (with switch on or in acc position). If the fuse shows power on both terminals then you have a bad connection behind the fuse block or a broken wire going to the heater switch. They are using a 14 gauge wire for this circuit which I personally think is way to small for what the blower fan will require. I believe you will find a bad connection behind the fuse block and I would replace that wire with at least a 12 gauge all the way to the switch.

 

I took the fuse block apart today and everything looked good. Put it back together and now it WORKS! Must of had a bad connection at the block. Thanks for all the help!

 

That is what I call an intermittent connection and will quite possibly happen again but maybe not. Queer electrons play differently...