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Misc electric issues on 73

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Old Oct 8, 2015 | 08:26 AM
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Default Misc electric issues on 73

Just a few issues with my 73 I want to get some input for. This is the 18k mile 73 I recently bought that was in storage on a lift for many years. Now that I am driving it, I have noticed a few minor issues.

- Horn does not work. Replaced the horn contacts and still a no-go. Where is the relay and what fuse supplies power to the relay?

- Front drivers turn signal has a bad ground. (left turn dash indicator is solidly on when lights are turned on, turn signal in drivers front left does not work, new bulbs, works when jiggled). Still looking at that one. Should be an easy fix after I get it in the air.

- Fan high speed does not work. Is there a separate relay for the high speed on the heater fan?

- Noticed my battery drains over a period of 4-5 days if left unattended. It was down to 5.4 VDC yesterday. This indicates a bad battery and will be replaced. The weird thing is the clock never lost time and is still accurate? How does a 12v clock run accurately on 5v? Weird.

Comments on where to start?

Thanks,
Rich
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Old Oct 8, 2015 | 10:35 AM
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Rich, some comments below,

Regards,
Nick

Originally Posted by Redhook98

- Horn does not work. Replaced the horn contacts and still a no-go. Where is the relay and what fuse supplies power to the relay?

This thread might interest you :
https://www.corvetteforum.com/forums...line-fuse.html


- Front drivers turn signal has a bad ground. (left turn dash indicator is solidly on when lights are turned on, turn signal in drivers front left does not work, new bulbs, works when jiggled). Still looking at that one. Should be an easy fix after I get it in the air.

I had same problem (bend the contact and so far so good)

- Fan high speed does not work. Is there a separate relay for the high speed on the heater fan?

Seems like horn & fan could be related (see posted link) There is a resistor controlling the speeds in both AC & non AC cars, it's mounted to the heater box

- Noticed my battery drains over a period of 4-5 days if left unattended. It was down to 5.4 VDC yesterday. This indicates a bad battery and will be replaced. The weird thing is the clock never lost time and is still accurate? How does a 12v clock run accurately on 5v? Weird.

Check for a drain as well

Comments on where to start?

Thanks,
Rich
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Old Oct 8, 2015 | 12:09 PM
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Hi Rich,
Perhaps you might check the ground wire at the horn too.
I believe in 73 the horn still had it's own ground.
Regards,
Alan

You can see the black wire passing over the horn bracket on it's way to that bolt with star washer in the headlight reinforcement to the right of the horn.
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Old Oct 8, 2015 | 05:20 PM
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For the horn, check all of the connections at the horn relay. They may have some corrosion that is preventing good contact. Also check the relay itself to make sure it still works.

Inside the clock, a small solenoid winds the spring when energized. After it unwinds (4-5 minutes), the solenoid engages and winds the spring again. It consumes very little power and can operate at lower voltages.

Check to make sure all of the courtesy lights are off when the car is not running. These will drain the battery in a relatively short time. Especially check the one in the center compartment of the rear tray.
Fran
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Old Oct 9, 2015 | 12:30 AM
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The '73 horn relay is located on the driver side fender well between the alternator and master cylinder.
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Old Oct 9, 2015 | 07:25 AM
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Thanks for all the input! The turn signal was a simple fix. Minor corrosion in the socket. Scrape of a knife and all is better.

Going to work the other issues this weekend.
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Old Oct 26, 2015 | 08:30 AM
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OK, here is an update. I checked the horn ground only to find the horn was not even connected. Feeling like a dumba$$, I connected it. Horn goes off in my face. Doh!

At the same time I was troubleshooting the power draw causing my battery to drain. While disconnecting the battery, I could hear the horn relay opening/closing as the battery cable bolt was loosened. Ah ha! Tells me something is shorted somewhere causing the relay to contact and thus maybe draining my battery over time.

Pulled the horn cap off and steering wheel. Pulled everything else down to the turn signal switch. No pinched wires that I could see. Wiggling the wires I could get to had no affect either. This column had been out before when the PO owned it. He had attempted to install a tilt/tele rack from Flaming River. This column was reinstalled when that did not work out for him. Was not a hack job and no wiring cut or mangled that I can see.

Obviously something is shorted in the horn circuit leading to the horn relay. This most likely is either the cause or helping the drain on the battery. For now I just disconnected the horn button connection on the relay so that relay is not constantly charged. Does anyone have a good diagram of just the horn circuit? The factory manuals diagram I have are a bit rudimentary.

As for the bad ground in the turn signals, it was just a slightly corroded connection. Cleaned it up and good as new.

Thanks!
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Old Oct 28, 2015 | 07:57 AM
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Originally Posted by Redhook98
The turn signal was a simple fix. Minor corrosion in the socket. Scrape of a knife and all is better.
Same here. I took a bit of sand paper to the bulb sockets in the tach and speedo housings and that fixed the signal and dash lights
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Old Oct 29, 2015 | 06:56 PM
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Originally Posted by Redhook98
OK, here is an update. I checked the horn ground only to find the horn was not even connected. Feeling like a dumba$$, I connected it. Horn goes off in my face. Doh!

At the same time I was troubleshooting the power draw causing my battery to drain. While disconnecting the battery, I could hear the horn relay opening/closing as the battery cable bolt was loosened. Ah ha! Tells me something is shorted somewhere causing the relay to contact and thus maybe draining my battery over time.

Pulled the horn cap off and steering wheel. Pulled everything else down to the turn signal switch. No pinched wires that I could see. Wiggling the wires I could get to had no affect either. This column had been out before when the PO owned it. He had attempted to install a tilt/tele rack from Flaming River. This column was reinstalled when that did not work out for him. Was not a hack job and no wiring cut or mangled that I can see.

Obviously something is shorted in the horn circuit leading to the horn relay. This most likely is either the cause or helping the drain on the battery. For now I just disconnected the horn button connection on the relay so that relay is not constantly charged. Does anyone have a good diagram of just the horn circuit? The factory manuals diagram I have are a bit rudimentary.

As for the bad ground in the turn signals, it was just a slightly corroded connection. Cleaned it up and good as new.

Thanks!
See if this any easier to read and good luck.
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File Type: pdf
Corvette 1973 wiring.pdf (349.7 KB, 120 views)
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