My apologies up front for repeated question on this topic. 1965 Corvette L76 no AC with 4 speed. Battery draws down after a day or too and measurement on draw down is 1.93 using 10A scale. Check alternator diode and 0 ohms one way and some measurement other way. Disconnect plug in field wires load to battery goes away when measured between disconnected positive and positive battery terminal post. After reconnect of plug in load returns. Unplug voltage regulator (solid state) load goes away., reconnect and it returns. Horn works fine and when power leads removed from Horn relay draws goes away. Reconnected horn relay and tried new Voltage regulator and load comes back. Tested horn relay with battery charger 12 volts and solenoid clicks as advertised. Issue noticed after engine reinstall, heater core replacement, LED dash bulbs installed. All original no after market radio or add-ons. Disconnected steering column half moon connections and wiper motor no change. Any suggestions appreciated. Battery also tested good when charged.

 

is your glove box light switch working?

 

Kevin - Welcome to the Corvette Forum. Lotsa help here on electrical stuff but let me kick it off by asking about the alternator. What voltage are you seeing a the battery when the engine is running?
I would guess that since you've done so much work to the car lately, corroded connections are not an issue?
**Just saw Keith's question about the glove box light...great suggestion to check**
Mike T - Prescott AZ

 

Leave the regulator connected and disconnect all wires on the alternator to see if the slow drain goes away.

 

Remove the bottom fuse and see if the draw goes away . . power for the clock, courtesy lights, and glove box lights (and brake lights) run through the bottom fuse, The clock, if not rebuilt, can cause a big draw.

 

Yes and even removed bulb. Pulled all fuses and still have draw. Thanks for reply

 

Alternator puts out 14.3 running

 

When either field wire (plug in) or voltage regulator connection are disconnected draw goes to zero. Same with horn relay on power wires. Any of the ones are disconnected draw drops to zero

 

Switch the DVM scale to AC volts, place across battery engine running at high idle and say what you read.

Dan

 

Think I am getting close. Pulled positive leads off horn relay and one goes to battery positive and second goes to alternator. Continuity good on both but battery to Horn relay when disconnected battery draw goes away. Horn relay to alternator no draw its on the battery to horn relay. (two red and one black and looks to be lime green wires. Will check wiring diagrams in morning.

 

Good job in sleuthing. Process of elimination working well. Hope the horn relay is your answer.
65-StingRay

 

Does the horn relay get warm when battery is connected and horn button not pressed? Do you feel a slight buzz on the horn relay when the battery is connected? I helped a friend with a 66 that had his wiring harness replaced by a restoration shop and they reversed the green and black wires on the side of the horn relay that run to the horn and to the horn button. Enough current was passing through the relay to run the battery down (and the relay got warm), but not enough to blow the horn after it passed through the coil of the relay. In that case the ground would be after the horns, so more resistance, less current. Easy check, leave everything else connected and disconnect the connector with the green and black wire on the horn relay. If the draw goes away, make sure the green wire that connects to the horn is on the relay connector that goes to the OUTPUT contact on the horn relay and the black wire that goes to the horn button is connected to the connection on the horn relay that comes of the thin wire at the base of the horn relay coil. If they are backwards, you will have 12v through the horn relay and horns to ground and run the battery down pretty quickly.
I'm not explaining the pathway clearly enough, but trust me, if those two wires are reversed, it will overheat the relay and run the battery down. (We are not talking about the black wire that connects to the red wires and feeds the battery gauge, this is the black wire on the side of the relay that connects back to the cabin to the horn button.)

 

Just jumping in as I have a similar issue with my 66 which has a parasitic 1.6 amp draw. First that is a fairly high draw, far more than what LED bulbs consume. The horn relay, as I understand it, has a dual role as a power distribution bus. There is a direct 10 gauge wire that connects to battery positive by way of the starter solenoid so that wire at the horn relay is always hot. From the relay, the "Big Red Wire" connects it to the firewall bulkhead connector and powers (I believe) the fuse panel which in turn powers a bunch of other things throughout the car. If you disconnect the horn relay you would eliminate the draw, assuming it coming from somewhere eles, because by doing that you took a bunch of things down stream out of the picture. Now to distinguish your problem from mine, on mine disconnecting the VR or alternator connections did not affect my draw problem. My working theory is that the ignition switch, which is old, may not be actually off when the key is off. This is a condition others have written about. When I have the chance I'll pull the wiring plug off the switch and retest for a amperage draw at the battery.

 

The difference is when he pulled the red wire NOT going to the starter (battery), the draw was still there, so it should not be in the cabin because the red wire to the fuse box was disconnected, if he explained the symptom accurately. All that left in the circuit was the starter solenoid and the horn relay. The horn role role as a distribution bus is that it connects the red wires together on the same electrical contact, it's a junction point for the red wires, nothing more. The relay itself only controls the horn voltage by closing when the black wire at the horn button grounds one side of the coil. So if I read the symptoms and troubleshooting done correctly, it has to be at the horn relay (or alternator if that red wire is not disconnected also)

 

That is a good hunch that I'd not considered. The reason I asked for a battery voltage reading set to AC volts is an appreciable AC voltage on the alternator output is a failed diode(s). If it is not a miss wired horn relay it is likely the alternator.

Dan

 

Horn relay is not getting warm and connector for horn is correct and working fine. Thanks for suggestion. Appeared the positive on horn relay with two positive leads when connected creates a draw. The red wires go to battery and second to alternator and third Black with white stripe goes to r/h connector then to radio capacitor

 

The black/white wire goes to one side of the battery gauge. If you disconnect the red wire going back to the bulkhead connector and leave the ones to the alternator and battery connected, do you have the draw?

 

Disconnected both bulkhead connectors and draw still there. I tested diode and have reading one way but not the other and appears charging with 14.3 volts but still suspect something is wrong with it. When power to it is hooked up and either field wires (plug in), power lead to alternator or horn relay power to alternator or regulator (solid state) is disconnected draw goes to zero. Horn relay is good, used a new replacement voltage regulator and no change thus I think alternator is bad even though diode test and charging test are all good. The black and white wire also on horn relay goes to R/H connector then to ammeter which was eliminated when connector was disconnected and still have draw.

 

I'll ask a third time. Have you placed your DVM set to AC volts across the battery with the engine running?

If the draw disappears whenever the alternator output connection is removed you found your problem, especially if the draw continues with the regulator connections removed. I suspect a leaky diode or a high resistance internal short in the stator.

Dan

 

Dan, sorry for delayed response was out of town a while. Long and short, no AC reading while running. Checked alternator out put and was still 13.6 to 14.2 on DC readings. Pulled alternator since its fairly easy and took to a shop to test on bench and they said diodes are bad. Using test o ohms checked good while in car but bench test showed they were bad so hopefully problem solved. Dropped both date coded 37A alternators off to get rebuilt. Fingers crossed his is the fix. Thanks for input!