A curious electrical situation - MYSTERY SOLVED!

700rpm

700rpm

Well-known member
I have repro headlights on my coupe, and after trying to make the repro sockets work, I gave up and hard-wired the lights so they work properly. But here is the curious thing: when the headlights are on, low or high, I get a 10 amp discharge while driving, rather than having the needle sit at zero, as it does on my other (original wiring) cars. I have a new wiring harness in, and my generator is set to charge at 10 amps for winter driving. I also have the 50-32 CP bulbs in the headlights and the 10 CP bulbs in dual tail lights, which I don't have in my other cars.

So, electrical wizards, is the additional candle power what is causing the greater discharge, or should I look for something else. And if that, what?

And what will be the consequence of this extra 10-amp discharge? Eventually a dead battery?

Electricity is a mystery to me.:rolleyes:
 
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Re: A curious electrical situation

Are both high and low beams lit wether it is switched to either one? I had this problem due to the pins being sloppy in the bulb socket. I made a new insulator that held the pins better and solve that problem. also how much is the generator charging with the lights off?
 
Re: A curious electrical situation

I think the bulbs are drawing enough to cause your 10 amp discharge. What does the ammeter read with the lights on and engine off?

What does the ammeter read with the engine running and lights off?
 
Re: A curious electrical situation

Tom Wesenberg said:
I think the bulbs are drawing enough to cause your 10 amp discharge. What does the ammeter read with the lights on and engine off?

What does the ammeter read with the engine running and lights off?
Click to expand...

Lights on, engine off: -10 amps
Lights on, engine running at driving speed: -10 amps
Lights on, engine idling: -10 amps.
Lights off, engine running at driving speed:+10 amps

Parking lights give the same reading as my other cars.
 
Re: A curious electrical situation

J Franklin said:
Are both high and low beams lit wether it is switched to either one? I had this problem due to the pins being sloppy in the bulb socket. I made a new insulator that held the pins better and solve that problem. also how much is the generator charging with the lights off?
Click to expand...

This was the problem I had before I hard-wired the lights. Now I have high beam, low beam, and parking, just as I should. I tried heat shrink and other insulation methods, but couldn't make them work.
 
Re: A curious electrical situation

That is a weird one, drawing 10 amps with the car/generator not running and 20 amps with the car/generator working.
 
Re: A curious electrical situation

I'm thinking it's the 50 cp bulbs. Any other suggestions?
 
Re: A curious electrical situation

50 CP bulbs won't kill the charging like that unless the generator has an issue or the battery has developed a leakage or internal short somewhere (likely a single shorted or leaky cell). If switching to lower CP bulbs "fixes" the problem, I would suspect a problem still exists that will show up again later when the problem becomes worse.

With the motor off, what is the battery voltage with the lights off and with the lights on? If that voltage varies by more than 0.75 volts, then your battery is the culprit.
 
Re: A curious electrical situation

P.S. said:
50 CP bulbs won't kill the charging like that unless the generator has an issue or the battery has developed a leakage or internal short somewhere (likely a single shorted or leaky cell). If switching to lower CP bulbs "fixes" the problem, I would suspect a problem still exists that will show up again later when the problem becomes worse.

With the motor off, what is the battery voltage with the lights off and with the lights on? If that voltage varies by more than 0.75 volts, then your battery is the culprit.
Click to expand...

The battery is new last year, but it could have gone south in that time, I guess. I have another gen I'll try, but I think I'll take the battery in and have the shop test that first.

Thanks, everyone, for your input.
 
Re: A curious electrical situation

700rpm said:
Lights on, engine off: -10 amps
Lights on, engine running at driving speed: -10 amps
Lights on, engine idling: -10 amps.
Lights off, engine running at driving speed:+10 amps

Parking lights give the same reading as my other cars.
Click to expand...

I sure don't know why the cutout would work with the lights off but not with the lights on. That is what the above data suggests.
 
Re: A curious electrical situation

700rpm said:
It is a diode cutout. Would that make a diff?
Click to expand...

Somehow I knew you would come back with that! Maybe Tom can come back with an idea why the generator is only working sometimes. Are you sure you didn't make any errors in entering your data?
 
Re: A curious electrical situation

Marco Tahtaras said:
Somehow I knew you would come back with that! Maybe Tom can come back with an idea why the generator is only working sometimes. Are you sure you didn't make any errors in entering your data?
Click to expand...

It is so strange that I drove it yesterday just to double-check that I had read it correctly. It is what I first wrote, and why it is so curious to me. :confused:
 
Re: A curious electrical situation

I'm still trying to make sense of the readings also. :confused:

Another way to check would be with the voltmeter.
Read the battery voltage with the engine off and lights off.
Read the battery voltage with the engine off and lights on.
Read the battery voltage with the engine on and lights off. (fast idle)
Read the battery voltage with the engine on and lights on. (fast idle)

Readings in tenths of a volt should be close enough. 6.4, 6.7, etc.
 
Re: A curious electrical situation

Check the fan belt tension and the generator pulley to armature connection. If there is slippage here the generator may only generate your 10 amps when it should be generating more. When an additional electrical load is placed on the system, slippage may increase to the point of very little generator output. Giving a discharge indication at the ammeter. Just a thought. Armchair diagnosis is poor at best...good luck.
 
Re: A curious electrical situation

Problem solved! And as usual, it was caused by junk repro parts. As I mentioned in my initial post, I have repro headlights, and I had given up trying to make the conduit socket connection work and had hard hardwired the lights directly, bypassing the sockets, which were shorting out because the spring connectors would get pushed against the housing.

Well, it turns out the same thing was happening in the bulb socket. I replaced the repro bulb sockets with originals, which had been kicking around in my parts drawer for who knows how long, and there was the answer. Things now work as they should.

Thanks again to all who made their suggestions, and I hope someone else can benefit from this experience. And again I say, don't throw anything away! Especially original parts. You never know when you might need them.
 
My bigest problem is that I have no idea whether the part is original or repro. My rig was "restored" over 20 years ago by person (s) unknown to me. I have only had it for a couple of years. Some parts I can obviously tell are repro, and not very good at that, but there are a lot of others I wonder about.
 
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