1973 Duster Heater fan not working

[scottbak]

I have checked the fuse

Got to the connector

But I do not get any power out of it using a voltmeter. Am I supposed to?
There is high, fan and off on this switch. Also it is only use black wire, Green and Brown. The red looks cut, but it goes into the same connect as the black. Could it be this? But where does it go then? I have the wiring diagram,

and

But I am totally lost here. I don't want to rip into the motor unless I have to. Also, where is the resistor? I looked under the dash by the heater box, but not there. Is it inside something?

Switch works, as I put an ohmmeter on it and it passed for both high, fan and off.

Thanks,

Scott

View attachment 1715564195

View attachment 1715564197

 

[Tanker]

Great. I was looking at the wrong part of the drawing. In the lower part there's a heating and air conditioning blower motor that caught my eye and I went from there. So let me rework this. According to your drawing the black wire going into connector CI 41(pictured in your photo) is carrying 12 volts from the fuse to the switch. The red wire is supposed to carry it on from there to another destination, but as it's been cut it is no longer doing that. The brown and dark green wires pictured in the same photo then continue on to connector CI 33 at the resistor block. At that connector the dark green wire passes through providing 12 volts to the motor for high or a reduced voltage through the resistor for low. A black wire coming from the blower motor also passes through connector CI 33 on its way to ground. Using your volt meter with power on and the switch in the high position you should be able to see 12 volts available on the blower motor side of the dark green wire coming out of that connector. If it’s there you can rule out the switch or power supply as the problem. From there confirm that your ground is good. In other words, with power off check continuity between the black wire at connector CE 33 and ground. Loss of ground can render the motor inop as well. If you have power and ground the issue is the motor. If you don't have power there the issue is somewhere up stream.

 

[67Dart273]

My advice is get into the AC service section of the shop manual. There are simplified diagrams and a little bit of writeup in there Section 24? I forget. The heating / AC section

 

[Tanker]

I forgot to mention, unless your car's been modified I believe the blower motor only works when the ignition is in the on position. If the ignition is on you should have power at the fuse. If you don’t there’s no point looking downstream. The problem is between the fuse and the battery somewhere. I notice that the same wire that brings power to your heater blower motor fuse also brings power to the rear window defogger system fuse. Does your car have that system and is it working?

 

[scottbak]

ok, let me test these things with the car running and see what I get. Also, yes I have a rear defogger, but have not tested to see if it works, as I live in Las Vegas and would never use it.
Also, quick question on the wiring diagram: so in the red circled (for example) it says C4 I4 BR, I get that the wire is brown, but what do the C4 and I4 (eye 4? or 14?) mean?

 

[scottbak]

My advice is get into the AC service section of the shop manual. There are simplified diagrams and a little bit of writeup in there Section 24? I forget. The heating / AC section

I have the shop manual, and yes section 24 is AC/Heat, I think I found it at 24-96. let me review that section, thanks! I was looking up wiring diagrams and not even looking in AC, since this is a NON-AC car. ;)

 

[Tanker]

ok, let me test these things with the car running and see what I get. Also, yes I have a rear defogger, but have not tested to see if it works, as I live in Las Vegas and would never use it.
Also, quick question on the wiring diagram: so in the red circled (for example) it says C4 I4 BR, I get that the wire is brown, but what do the C4 and I4 (eye 4? or 14?) mean?
View attachment 1715564667

Most good schematics will label the wires with letters, numbers or a combination of the two so that the wire can be more easily traced through multiple pages or very busy drawings. The C5, C6, C7 etc are the labels. The other figure is likely a call out for the wire gauge. The numbers 14, 16, and 18 are common wire gauges with the smaller numbers being thicker wires. As you've already guessed the other letters are color call outs.

 

[scottbak]

Most good schematics will label the wires with letters, numbers or a combination of the two so that the wire can be more easily traced through multiple pages or very busy drawings. The C5, C6, C7 etc are the labels. The other figure is likely a call out for the wire gauge. The numbers 14, 16, and 18 are common wire gauges with the smaller numbers being thicker wires. As you've already guessed the other letters are color call outs.

Thanks, this will help. So I traced the black wire and found it was also cut. on the fuse box, Heat Fuse, used an ohmmeter to track it to #12 on the pad behind the fuses and it's wire is purple. *ZOINKS* Anyways, I need to see where that purple wire goes next.

 

[scottbak]

Thanks, this will help. So I traced the black wire and found it was also cut. on the fuse box, Heat Fuse, used an ohmmeter to track it to #12 on the pad behind the fuses and it's wire is purple. *ZOINKS* Anyways, I need to see where that purple wire goes next.

Yep, nope. Ran a new red wire to the fuse box #13 and then to the connector for the Fan switch. Hmmm, blower motor turns, what do you know. Thanks for all your help!