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Author Topic: High Voltage at Battery  (Read 1023 times)
W4ATL
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« on: November 02, 2017, 01:50:05 PM »

My '68 Charger has had high voltage, about 16 VDC, at the battery for a while so I decided to investigate. I have a digital Fluke multimeter so I can make some precise voltage and resistance measurements.

The first thing I noticed from the schematic of the charging circuit is that the voltage regulator measures the voltage from Ignition 1. This voltage was correct, about 14.8 volts, but the battery voltage was almost 16 VDC. Ignition 1 goes through the ignition switch so I measured the resistance from the Ignition 1 connector to the regulator to the disconnected positive battery terminal and it was about 0 to 5 ohms, depending on how I wiggled the key. Not good. I ordered a new ignition switch and replaced it. Now the resistance is essentially 0.

The new ignition switch helped the problem but the voltage at the battery was still high - about 15.3 volts. I poked around further and noticed that I had wired the electric choke into Ignition 1 for power. Not good, since that electric choke draws a lot of current. I moved the power to a fused port on the fuse box inside the car and now the voltage is correct - about 14.8 VDC when cold.

Aside from my mistake in wiring the electric choke, you need to make sure that the ignition key is good and has a very low resistance in the run position. This is something that I have not seen in other posts about high voltage problems. A digital voltmeter will help check the resistance and voltage drop in these circuits.

In order to replace the switch, I had to remove the dash so I could get my hand in there to disconnect the connector and remove it. The lock mechanism can be removed by inserting the key, push in a little brass pin near where the key is inserted, rotate to run position and the ignition lock will come out. Reverse the procedure to insert the lock mechanism into your new key.
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BLK 68 R/T
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68 Charger R/T, 493 stroker engine, 727 auto.


« Reply #1 on: November 02, 2017, 02:23:36 PM »

My '68 Charger has had high voltage, about 16 VDC, at the battery for a while so I decided to investigate. I have a digital Fluke multimeter so I can make some precise voltage and resistance measurements.

The first thing I noticed from the schematic of the charging circuit is that the voltage regulator measures the voltage from Ignition 1. This voltage was correct, about 14.8 volts, but the battery voltage was almost 16 VDC. Ignition 1 goes through the ignition switch so I measured the resistance from the Ignition 1 connector to the regulator to the disconnected positive battery terminal and it was about 0 to 5 ohms, depending on how I wiggled the key. Not good. I ordered a new ignition switch and replaced it. Now the resistance is essentially 0.

The new ignition switch helped the problem but the voltage at the battery was still high - about 15.3 volts. I poked around further and noticed that I had wired the electric choke into Ignition 1 for power. Not good, since that electric choke draws a lot of current. I moved the power to a fused port on the fuse box inside the car and now the voltage is correct - about 14.8 VDC when cold.

Aside from my mistake in wiring the electric choke, you need to make sure that the ignition key is good and has a very low resistance in the run position. This is something that I have not seen in other posts about high voltage problems. A digital voltmeter will help check the resistance and voltage drop in these circuits.

In order to replace the switch, I had to remove the dash to I could get my hand in there to disconnect the connector and remove it. The lock mechanism can be removed by inserting the key, push in a little brass pin near where the key is inserted, rotate to run position and the ignition lock will come out. Reverse the procedure to insert the lock mechanism into your new key.

Shouldn't have to remove the dash  shruggy
undo the retaining ring on the front, pull entire ignition assembly out the back and drop it down, replace parts as needed, reverse procedure.
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W4ATL
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« Reply #2 on: November 03, 2017, 04:20:52 AM »


My car has A/C and it was impossible for me to get my hand up in there and remove the connector and key. Believe me, I tried....hard. I really didn't want to remove the dash.
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MoParJW
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« Reply #3 on: November 03, 2017, 06:15:25 AM »

I had similar problems.
After replacing the IGN1 & 2 wires, and the ignition switch, the engine also ran noticeably better, and no more burnt points (this is even covered in the FSM, I found out later).
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'68 Plymouth Satellite sedan 318
John_Kunkel
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« Reply #4 on: November 03, 2017, 11:15:58 AM »

I poked around further and noticed that I had wired the electric choke into Ignition 1 for power. Not good, since that electric choke draws a lot of current.

What do you consider "a lot of current"? I've tested both Holley and Edelbrock choke heaters with a quality VOM and found the initial current draw to be about 6 amps for a millisecond and then dropped off to 1.5 amps. After that, as the coil heats up, it steadily dropped from 1.5 and leveled out at about .80 amps.

I've always wired the choke to the blue IGN1 circuit and never had charging problems.
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Pardon me but my karma just ran over your dogma.
W4ATL
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« Reply #5 on: November 03, 2017, 12:34:23 PM »

6 amps is a lot of current. It was enough to drop the voltage at the regulator and cause the battery voltage to be high. It might have been OK to leave it, but I went ahead and moved it in order to drop the initial voltage when cold.
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