Overvoltage

[Wedgetail]

I took my ‘40 Deluxe out for a quick drive to try out the wheel alignment. After about 1/4 mile it started running really rough, lost most of its power and the battery gauge pegged high, and the coolant temp pegged low. (Oil and gas gauges were ok). I limped home, and in the garage, revving the engine causes the battery to get over 8 volts (and the headlights brighten with RPM). Until recently, I wasn’t even convinced that the generator was charging the battery, and I’ve never seen anything over 6.3V. Why all the voltage?

[deuce_roadster]

I would suspect the V reg.

[koates]

With the engine revved up a bit you should be reading 7.3 to 7.5 volts at the battery terminal on the voltage regulator. Set your multimeter on DC Volts, not AC. Regards, Kevin.

[Wedgetail]

Previously, I had never seen anything above the low 6’s and wondered how the battery stayed charged, now I’m seeing over 8. Sounds like it’s time to try a new regulator.

[fortyfords]

And good luck on finding a good USA regulator, if it's the original regulator, take the cover off and clean the contacts and see how it works then.

[Wedgetail]

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It’s not the original, it says “Allstate” on the cover. I took the cover off and cleaned all the contacts, and it didn’t make any difference. I have a new one on order from Dennis Carpenter, we’ll see how that works.

[koates]

Maybe its not your regulator at all and the generator is not making enough volts. No use just guessing and swapping parts. To test the gen just remove the field wire from its reg terminal and connect it over to the armature terminal on the reg. Rev her up a bit and your voltage at the battery terminal on the reg should go quite high (over 8 volts) if the generator is OK. If you still dont get above 6.5 volts then the generator is faulty. Regards, Kevin.

[Bill OH]

Use an analog volt meter - a digital voltmeter will give a false reading because of ignition interference. Remove regulator cover, connect voltmeter to battery term on reg and adjust the spring tension on the voltage control opposite the field terminal to 7.2 volts. Try that.

[solidaxle]

When trouble shooting, I go for the easy things first. Try polarizing it.

[solidaxle]

Originally Posted by Bill OH

Use an analog volt meter - a digital voltmeter will give a false reading because of ignition interference. Remove regulator cover, connect voltmeter to battery term on reg and adjust the spring tension on the voltage control opposite the field terminal to 7.2 volts. Try that.

People look at me funny when I break out my old Simpson 260. I love it.

[petehoovie]

Originally Posted by solidaxle

People look at me funny when I break out my old Simpson 260. I love it.

[rotorwrench]

What meter were you getting the lower voltage readings on? Does your 41 have an Amp meter or a Battery meter in the dash. If it's an Amp meter then it may have a short some place. That would play hell with the charging system and could do damage. A short will generally pop the circuit breaker but I have no idea if your car is still all stock or not.

The voltage regulator maintains the voltage as was mentioned in the 7.2-volt range if it's working properly. Low voltage is a sign that it wasn't working properly. There is also a current limiter in the VR box as well as a battery cut out. If the battery was managing to barely charge then it was set so low that it's a wonder that the cut out let the generator even come on line. The cut out doesn't come on line until the voltage in the generator is higher than the battery voltage. That's usually around 6.6-volts. I'd be wondering about the accuracy of the volt meter. If it was accurate then the voltage regulator control unit was likely needing a change some time ago.

[Wedgetail]

It’s a 1940 deluxe with the original dash gauges, so the battery gauge shows voltage, and I’ve calibrated it with a digital volt meter. I don’t have anything as classy as the Simpson shown above. The gauge used to hang out just between red and orange, which was low 6’s, and when it pegs high, that is 8+ on the DVM. The dash gauge is slow to respond (being based heating a resistor), but seems remarkably consistent. I think you are right that the regulator was running low before, and has now given up the ghost. The new one has just arrived in the mail, so that’s the next step. (I know the generator works because I’m seeing the high voltage 8V even without disconnecting it from the circuit).