heater isnt working

[1971ford]

well its cold now i guess its time to fix the 71's heater.
i took the factory heater/ac out and sold it, and swapped in a heater out of the old parts truck and the heater-only controls. i hooked it all up and i cant get the fan to turn on so i bought another working fan, swapped it in , no worky. so i popped all the fuses and checked them and they are all good. i ensured all the plugs were firm on the heater and control switch, and that the power plug was firm in the other plug. and the fan was grounded good and was connected to its power wire.

i have an electrical tester but not too sure how to test things with it
i put the + and - tester shanks in the plug that goes to the controls switch and i got it to say something like .02 or .2 i forget which. so thats SOME power atleast right? i cant remember 100% but i thought the heater worked fine when it was in the parts truck so the fan shouldnt be broken.

so i guess im asking how to test for power getting to places and where to test. and what wires to check to make sure are connected and stuff. gosh i hate electrical

[fordman]

when you done the swap did you change the controls also? if not maybe that is the problem. the only other thing i can think of is to swap fan switches. you should have power coming into the switch. and when you flip the switch you should have power coming out to the motor. its pretty simple if you look at it that way.

[Thunderfoot]

Ryan,
Put the (-) to a good metal (ground) connection, like the dash or something metal unpainted. Then use the (+) just like you would a test light and check the voltage reading. Make sure the scale setting on your tester is set so that it will read 12V and that the tester is set to read DC volts.

Check that you have 12V at the switch with the key on and then check that it is getting out of the switch. Then check the voltage at the fan motor, it should be 12V when the switch is set to HIGH, but for medium and low it will read less then 12V respectively, as less voltage makes the motor turn slower… That is what that resistor pack is for on top of the box, to cut the voltage down for the slower speeds.

[1971ford]

thanks, i just got back in from investigating with the electrical tester. i eventually found that i was getting 12v into the fan on "high" and the ground wasnt good enough, it was painted over and it was getting to bare metal. so i took the wire out from under its fan screw and i touched it to a bare piece of metal on the dash. a couple sparks and the fan was turning on high. moved the switch to low and the fan slowed a little like normal. so i got the grinder and made the screw/wire contact surface nice clean bare metal and i screwedthe ground back on. fan now doesnt work so i take the wire out from the screw again and i touch it to the dash. this time abunch of sparks fly from where i contact it to the bare metal and for the few seconds i did that the fan didnt come on.

wwhhhhhat da heck

[fordman]

try it again. maybe it blackened the bare metal when it sparked. if you know for sure you have a good connection check the fuse and go back through the whole process again. checking it all out. if still nothing maybe the resistor or fan burned out.

[1971ford]

ok so i got the fan working 100%. i dont know 100% what was wrong though. but for some reason, the ground i was using on the heater/fan where i had ground the paint off to bare metal wouldnt ground it. its baremetal, i dont see why it didnt work. but when i took the ground wire and touched it to the glovebox latch it would turn on, and i could rub it and press it onto the fan bare metal and it wouldnt work. so i grounded it to the glovebox thingy. also, i had to put a spacer on the left side of the fan mounting because for some reason if you push the fan a little to the left it hits something. i think when i was trying it earlier the fan was jambed against the heater box or something, im curious as to what it was hitting.

but now i have the controls all setup so the coolant cable opens up the valve all the way and closes all the way and i have the defroster vent jammed open and the other vents closed since i spent way too much time trying to get the cables right. and all ill need to use is defroster.

[Thunderfoot]

Glad you got it working.
If you were trying to ground the wire to the fan motor casing itself that wouldn't work, as the heater box that it is mounted to is not conductive... so no connection with the truck ground… The wire has to go to metal on the truck as you discovered getting it working. (if I understood what you were saying there, if not it is good info for others)

Where you had MORE sparks the second time you were touching the ground wire to the truck and the fan was not working, sounds like the fan was jammed where it couldn’t turn alright. This is why you had bigger sparks, as the motor was drawing more current trying to turn.

That is the end of your sparky lessen for today.

[1971ford]

Glad you got it working.
If you were trying to ground the wire to the fan motor casing itself that wouldn't work, as the heater box that it is mounted to is not conductive... so no connection with the truck ground… The wire has to go to metal on the truck as you discovered getting it working. (if I understood what you were saying there, if not it is good info for others)

Where you had MORE sparks the second time you were touching the ground wire to the truck and the fan was not working, sounds like the fan was jammed where it couldn’t turn alright. This is why you had bigger sparks, as the motor was drawing more current trying to turn.

That is the end of your sparky lessen for today.

it alllll comes together now
ground doesnt work on metal when the metal is connected to plastic
it does on the dash because it connects to truck's ground
ground makes sparks when fan is jambed and draws more power
fan is jambed on heater box because its not sitting right