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Topic: battery drain

in Forum: C3 Electrical

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battery drain (1/5)
10/21/14 8:22pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

I seem to have a battery drain.

I took off the negative terminal wire and put a test light between the terminal wire and the post and it had a bright light. I think this is the old school way you do it to check for shorts and battery drain.

This is a 1968 and they seem to have their own way of doing things.

Just would like to know what is hot and not when the ignition switch is off.

With positive and neg cables attached to the battery as normal, and with ignition off, I have power on the main lug on the starter coming directly from the battery.

The horn relay is hot, along with the alternator. The alternator had been changed out to a 120 amp alternator and the cable from the battery at the starter goes through a high rated fuse and onto the alternator. So maybe this is expected to be hot because it is tied into the battery cable at the starter.

The ignition and dash wires connected to the horn relay are also hot.

Does all these wires suppose to be hot when the ignition is off. Seems like this all could be a drain on the battery.

Any suggestions.

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Re: battery drain (2/5)
10/21/14 10:20pm

Adams' Apple

Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 20128

Horn relay is powered all the time(on some terminals only), since it is basically a junction block for power distribution to other areas of the car. Main feed wire at the alt is also always hot.
Inside the cockpit, the ciggy lighter, and clock are always hot. Clocks have been known to stick the points, and drain the battery. They have also been known to cause fires when the points stick. Shocked

Best way to see what is causing it is to start pulling fuses, one at a time until the drain goes away. Then you know what circuit the drain is on. If pulling all of the fuses doesn't determine the drain, then disconnect the battery feed at the alternator, as see what happens. Thumbs Up

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Joel Adams
C3VR Lifetime Member #56
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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Re: battery drain (3/5)
10/21/14 10:47pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

Great idea, I will check this out tomorrow. Thanks!

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Re: battery drain (4/5)
10/22/14 12:03am

daveo76
Former Member
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 857

My drain was coming from my factory alarm system. I don't think they were standard in '68, but perhaps your has one? I can let mine sit for a month now and it will still start (at least in the summer months). And Joel's suggestion of checking the clock is a good one, especially if it is the original mechanical beast - even if it doesn't work.

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1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

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Re: battery drain (5/5)
10/23/14 8:47pm

rlu1968
Former Member
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Gordonvillle, TX - USA

Vette(s):
1968 Roadster 427

Joined: 11/28/2003
Posts: 228

No alarm system, the clock has been converted. Took out the fuses one by one, no problems here. The alternator wiring is fine.

I have double wire going to the horn relay. Orange and black. The orange changes into a black and white wire that looks like it goes to the amp. gauge. The black wire goes into a red wire and looks like it will go to the ignition switch. When I removed this red wire it basically shuts down everything going to the electrical system of the car.

And this wire stopped the drain. So I think it might be in the ignition switch.

I had replaced all the dash wiring and instruments, but the ignition switch, was an after market and would not fit correctly to the 1968 switch harness. The aftermarket switch was turned incorrectly and the lugs of this switch would not line up with wiring harness legs that fit into the switch I notified the vendor and mfg. company, but who knows if this was corrected.

Next step is checking out this switch and maybe going back with a NOS, instead of the incorrect reproduction.

The amp gauge has been converted professionaly into a battery gauge, and this should not be my problem.

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