The Stovebolt Site Forums The Shop Area The Electrical Bay 1946 Chevy 1/2Ton - Engine First Break-in Run

I did my first break-in run today and noticed some things, but the floor is still dry - so that's a plus. 1) I checked the battery voltage while the engine was running (1500rpm) and it was 15.4 volts. Then at the end of the 15 minute break-in, it was reading 16.2 volts before I shut it down. Now battery is reading 12.77 volts with engine off. Should I be worried? 3-wire alternator is new, but 23+ years old. 2) I installed a little red LED light in the Excite wire from the alternator, but it does not turn off after the engine is running. Does the LED bulb not draw enough voltage and should I swap in a regular light bulb?

Just searching tonight and read that I should use an incandescent bulb on the excite wire and not an LED bulb. But then I read if the excite wire goes to the Accessory port on my ignition switch (which I can turn on/off), I don't really need the light bulb?

No, if you have a voltmeter that will register the ALT. working.

As was hoping if I swapped out the LED for an incandescent or just eliminate the bulb, the alternator might charge at 13.5 to 14 volts? Thinking maybe the excite wire with LED might be confusing the alternator to charge at the higher rate. I was watching a video last night that showed the bulb coming on when starting the car, but going out when the engine got running. Made me wonder why my LED was not turning off.

the 15 and 16 volts measured can lead to overcharging/heating and battery failure. I`d worry about that.
12.77 volts is good for engine off.

Those running voltages are too high. Anything above about 14.5 volts against a fully charged battery indicates the internal voltage regulator in the alternator is probably shorted out and producing full field current to the rotor winding all the time. That could also account for the indicator light not going out on shutdown. You probably need to rebuild or replace the alternator, or at least install a new regulator module.

www.ebay.com/itm/190774376868?

Jerry

Thanks guys. I found an incandescent indicator light today and I'll swap it with the LED light. I'm going to start up the engine one more time to see if that changes anything. If not, I'll look to replace the alternator. There use to be an automotive electric shop locally, but they closed down years ago and I'm not sure if there's another nearby.

The battery in Little Red exploded when I tried to start it after it had been driven 30 miles or so with a overcharge of 15.5.

You shouldn't get any more than 14.5 volts on your meter while the engine is running. A fully charged battery can register 13.3 or thereabouts, but 12.86 is considered fully charged

I picked up a new alternator (same model) and it was charging at 15.3. I also had the previous alternator bench tested and it passed. Wondering which 12v alternator others are using out there? The one I'm using is a Duralast DL7127M. Then I've seen the 1-wire vs 3-wire debate.

GM 1 Wire Alternator Self-Exciting 100 amp. 100 may be overkill but it works. $95
. A GM 1-wire self-exciting alternator, often a modified 10SI model, simplifies wiring to a single battery connection for power, removing the need for external voltage regulator wiring or ignition excitation. It automatically "excites" (activates) the charging system once the engine revs past a certain RPM, typically 1500

I have one of these small alternators due to space requirements, it works good for my truck.
https://brillman.com/product/12-volt-small-1-wire-alternator-40-amp-negative-ground/

Thank you Joe! I'm not running anything extra on my truck and I was looking for a 63 amp alternator. But, maybe 40 amp is plenty?

40 amps is 33% more than most of the original equipment generators produced. Unless you have a bunch of high current draw accessories like a bazillion watt sound system and/or a pair of high-wattage halogen headlights, you should be good to go!
Jerry

Good to know. Thanks Jerry!

Update: I did order a one-wire 63 amp alternator from Summit today. I'm going to try the one-wire setup. I'll let you guys know if the charging voltage is between 13.5 and 14.5 volts.

I was looking at an ACDelco 334-2614, but Autozone doesn't carry it anymore. (Since I had a new alternator from Autozone, I was trying to setup an exchange. No one seem to be able to help me with a one-wire alternator. If it doesn't tell them on the computer, then they don't know.)

AutoZone offers several 10SI-style Delco Remy alternators, often sold under the Duralast brand or as performance upgrades, featuring 63 to over 100-amp outputs. Popular options include the Duralast DL7127M (63 amp)

OK, I have story. I've been trying to use a DL7127M that came with my 12 volt conversion kit from 23 years ago. Next, I picked up a new one from Autozone and both were showing over charging. Autozone tested my original alternator and it passed. Not sure why both are over charging. So, I decided to try a one wire alternator setup and ordered one from Summit yesterday. Then, from just being frustrated, I started searching the internet again looking for 1-wire vs 3-wire alternators. I saw a guy on YouTube and he was talking about the wiring where the DA plug goes. He was connecting from one blade to the BAT terminal on the back of the alternator and I thought, "My red wire doesn't go like that". Then he mentioned if not wired correctly, it could cause over charging. I checked my DA plug and the two wires are reversed! I de-pinned and swapped them. Now everything looks to be working like it should. The little dash light I added comes ON when you turn the key and goes OFF when the engine starts.

So frustrating that someone probably assembled my DA Plug wire at 4:59pm on a Friday! Now I'll do another "Break-in" cycle and watch the charging to see if stays in range.

Thanks again to everyone that hung in there to help resolve the problem. I guess I'll keep learning about this old truck of mine.

Glad you figured it out John!

I'm surprised it puts out that much voltage at 750 RPM.

I'm planning to do some break-in runs tomorrow and see if it stays the same. I was wondering if my battery voltage is low, does the alternator put out a little more to help get it charged? Also, is there a break-in period for the alternator?

Great to hear you solved the mystery. Your alternator doesn’t need a break in period.

I’ve used YouTube to help me rebuild or solve allot of issues but it’s frustrating to me, how many you have to watch before you find one that is helpful. Some posters don’t care if the content they post is correct or not.

Thanks Phil. Yes - I watched many alternator videos and so glad this particular one clicked with me to check the wiring of the DA plug. It also showed that you don't have to connect the excite wire and your alternator will still charge if you rev up the engine a little. You won't have an indicator light, but the alternator will still work. Not doing that right now, but hope that was good information too?

John,
So glad you watched that video and back on track again. Way to be patient and hang in there. Now you are definitely getting closer for a ride. I use YouTube quite a bit. I like to see 2-3 doing the same thing. Gives me confidence to try what they offer.
Glen

a voltmeter should be used with a ALT. It'll tell you 2 things. The condition of the battery and the ALT output.
Yours may not have a cig lighter but this works well. I can put the original cig lighter back in
for looks most of the time. This one blends in pretty good.

I do have a space for a cigarette lighter. A small voltmeter would be nice to have. Where did you find yours?

I don`t see my particular one anymore on amazon, but you can search for cigarette lighter voltmeter.
Wired to an ACC spade

OK - I'll see what I can find. Thank you.

There are lots of choices on Amazon. Here is one example.

Thanks Phil. Not to pricey. I like that.