Electrical Gremlins

C

Classics Fan

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I want to start out by saying I am not naturally electrically inclined. I understand some of the very basics but get lost in my own pretty quickly. So here are my two issues:

Heater blower: doesn’t work in any of the 3 positions. I checked the fuse and replaced it even though it appeared good without success. What’s a logical approach from here? I have A/C with all the associated ducting under the dash. I don’t want to blindly start tearing things apart without a game plan.

Horn: neither works. I thought it was the horn relay so replaced it with a new one but that didn’t fix the problem. There is 12.9 volts (engine off) at the relay. When I ground out the trigger wire coming from the steering wheel horn button, the relay buzzes (key in ignition warning, puzzling) but no horn. Where do I go from here? TIA!
 
You possibly have a burnt out blower motor resistor. Look under the hood, passenger side, on top of the heater core housing.
Did you remove the horns and test if they work?
 
The horns look to be a bit of a PIA to access behind the lower valance so I haven’t touched them... yet. After posting above I put direct battery power to the two wires leading to them from the relay. One horn is completely dead and the other barely squawks. Clear direction here.

I found the resistor. It looks original. What is it’s purpose and how dot I test it?
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Remove the resistor and see if there are breaks in the coils.
 
No go. The connections were very corroded so I was hopeful but the blower still doesn’t come on. The coils are all good. Where from here?
 
Do you have a test light or voltmeter?
Do you have the 1968 Service Manual?
 
Yes and yes. I’m finding the service manual less than helpful in this instance but maybe I’m not looking int the right places.
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Service manual chassis electrical section has wiring diagram for your car. Check both sides of the fuse for power, than the switch for power going in and depending on speed selected power going out, then power out from the switch, power in to the resistor and out to the blower motor. You could also go directly to the motor and check for power.
The AC duct has small extension held on with a screw on the driver's side. Then there are 3 screws holding the large plastic duct to the bottom of the dash.
 
That sequence of operation is exactly what I need at this point. I’ve pored over the chassis wiring diagram and just don’t see that circuit. It would be a huge benefit if I understood electrical symbols. Thanks as always. I’ll no doubt be back on either this subject or another one!
 
Try this diagram
 

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  • 68 Wiring Diagram Page 4.jpeg
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You’re the man! Last (maybe) question for now: there is an oval snap-disc type switch mounted on the passenger cowl just above the AC housing. Any idea what that controls? I’m facing some wire color challenges since the PO painted the firewall without any regard for masking or taping.
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can you try posting an image
 
It is an ambient temperature switch and prevents AC compressor engagement below approximately 50 degrees.
 
I wanted to follow-up on my blower problem. Like I said at the beginning of this thread, I am not naturally electrically inclined. However, melsg5, with your explanation of the operational sequence together with the wiring diagram you provided I was able to chase the circuit fault to the blower relay. Power in, none out. I jumpered the relay and the blower came on. New relay is on order.

I really appreciate all your help, all the time - thanks!
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Thanks for the update glad to hear you found the problem
 
Classics Fan said:
I wanted to follow-up on my blower problem. Like I said at the beginning of this thread, I am not naturally electrically inclined. However, melsg5, with your explanation of the operational sequence together with the wiring diagram you provided I was able to chase the circuit fault to the blower relay. Power in, none out. I jumpered the relay and the blower came on. New relay is on order.

I really appreciate all your help, all the time - thanks!
Click to expand...
Was the relay coil receiving power?
 
NorCal65 said:
Was the relay coil receiving power?
Click to expand...
Yeah, power in but not out. The new relay was installed today. Good news: blower works! The bad news: heater control doesn’t. It appears it’s not getting vacuum as the blend doors aren’t moving and I don’t hear vacuum when the control lever is moved between selections. Tomorrow I’ll chase where the control gets it’s vacuum so there’s more than just ambient temp air blowing.
 
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