electical problem

[71bigblock]

Hi all electrical people more advanced than me.  I checked my fan switch (71 chally w/ a/c) with the ohm meter, and Im not getting a connection when I switch it either way.  Also, the three prong plug that plugs into the switch, Im assuming that the power comes from the black and white wire, and is either sent to the dark green or light green, depending where the switch is set.  I checked for voltage from the black and white wire, and I get 9 volts.  WTF??  So I checked the other two, and I get 3 volts on one, and 5 on the other.  Keep in mind Im checking the voltage on the plug that plugs into the back of the switch.  I have not heard the fan run, I just bought the car.  Any ideas would be much appreciated,

Steve

[Bullitt-]

Mine is non A/C but I had a similar problem, Power in, none out. I was able to bend back a couple of tabs & disassemble the switch, clean, lube & reassemble. Problem solved.

[71bigblock]

Thanks bullitt, I did just as you did.  It looked like the plastic piece that slides inside was just a touch melted, enough to make the plastic look shiny.  I cleaned with fine emry and reassembled, still no fan.  It makes me wonder why the switch was a touch melted, perhaps problems somewhere else?  Any more help would be appreciated.

Steve

[Chryco Psycho]

if you clean the contacts you should be able to test it with an Ohm meter to make sure it has contact across the switch

[1 Wild R/T]

The Blk/Wht wire should have 12v if it's an A/C car (I think it is) that wire is jumpered into the A/C harness above the ashtray, check the connector to see if it is burnt...These cars ran to much current through the switch originally & are prone to problems, I like to feed the high speed blower mode through a relay that way the switch sees reduced current in the high mode, in low & med speed the resistor reduces the current flow protecting the switch...Adding a bosch relay you can use the original high blower feed wire as the control wire for the relay coil (pin 86), ground the other side of the coil (pin 85), feed 12v to the power in (pin 30) & hook up the power out (pin 87) to the high speed fan connection..

[422STROKER]

You need to check a diagram for the proper wires to supply power.  Check those wires individually to ground not together.  I.E. Black to ground  White to gound etc.  Although I'm not sure if the switch needs a ground on A/C cars.


Tom

[71bigblock]

Thanks guys, I figured the problem may now lie in the reostat thingy.  I hot wired the blower and it does work.  We'll see 

[1 Wild R/T]

The rheostat thingy is the resistor that reduces the current making the lower speeds, high speed should bypass it entirely...I suspect you have a blower motor that is drawing too many amps which burned the contacts on the blower switch high position (common as the switch will only take 5-6 amps & a new blower motor typically draws 5-6 amps, (the reason I suggest adding a relay) & the resistor can also be damaged by excessive current draw from bad motor...So to fix it right your looking at the switch (you've repaired that-hopefully) a resistor, a blower motor & adding a relay...

[71bigblock]

Thanks wild r/t.  I did finally get the switch fixed, a very poor part to begin with.  I did finally find the problem, the wire from the fuse panel to the switch is bad.  I took 12 volts, put it on both wires that go on the back of the switch and I get low and high speeds.  I dont know why I didnt try that in the first place.  Whats the best way to replace a wire in the harness, or should I just bypass the harness, run a new wire until I restore the car?  Thanks,

Steve

[MEK-Dangerfield]

There is no problem bypassing the harness and running your own wire. I've done that.  Just make sure the wire has a fuse in it. You don't need an accidental fire to make your life interesting. 


  Mike

[71bigblock]

Problem solved!  Soldered a new wire in and viola!  It works