1 wire alternator install problem.

[Linda]

Check the connectors under the driver side dash. If dirty or loose you won’t charge.
Linda

[JT68]

Sorry for the confusion, this is a 3 wire GM alt set up. People in the internet kept calling it a 1 wire but it really is the 3 wire set up we have in the wiki.

I was testing things since it was weird that I only have a few volts at the alt on the battery terminal so I disconnected the wire at the fuse and it test at 12.3v, I took the wire off the alt and it was 12.3 but as soon as I touched the alt it fluctuated between 1 and 3 volts. So I grabbed the other alt and grounded it and hooked the power wire to the batt terminal and it stayed at 12.3v so I swapped the alternator thinking the new GM alt was bad. Now with the other alternator on, and car running it was at 12.3-12.5v but when I revved the car it jumped to 35-45v so I turned the car off. This was the one I bought off eBay that was said to be a 1970 Datsun roadster alt but has nothing on it to tell what it really is. It looked just like the GM alt I bought but I guess it's not since it doesn't appear to be internally regulated.

My new voltage regulator showed up from Datsun parts so put the stock alt back on and took it to the auto parts store to have it tested and they say it's still my voltage regulator that is bad. The kid that tested it didn't know what it meant but his computer said it was the regulator or diode that was bad. I have tried a few other regulators so I doubt all of them have been bad. I still think it's an alt problem.

How do I test the voltage regulator? I can keep the old stock alt on if I know the regulator is working or I can swap to the eBay alt and run the external regulator but I don't want to kill another battery. I wish I knew JT sold alts too, I would have bought one and saved time and money.

You've got a lot going on here....

I would bet the new regulator is fine - they get blamed as bad when its really just bad connections or wiring whether in the harness or alternator or wherever..

It does sounds like there could be multiple issues at hand....

I'd suggest to get a handle on what is good an what isn't. You can pm me a photo of the "70 Roadster" alternator an I can decode that mystery.

For the GM alt you bought, suggest just taking it to Autozone or O'reilly or any car electric shop and have it tested on an alternator machine - rule out a bad alternator.

Your easiest play is probably to get the 3-wire gm working wired directly to the battery as I outlined earlier in this thread. You can pm if you want me to help you directly.

j

[Lorna c]

good luck . you'll get this .

[redroadster]

Most parts stores will test free
Does the rotor feel magnatized with a screwdriver?

[aclever1]

So I'm back to work on this. I fixed my blinker issue, it wasn't electrical, it was the pin holding the lever on was coming out and stopping it from making a full range of motion to trigger the blinker.

For my alt problem, I've taken all 3 alternators in to the auto parts store and tested off the vehicle and all 3 passed.

The main wire that goes to the post on the alt only has 4-5v when the power is on or off so that might be my problem. I rewired the inline fuse on it to make sure its no the fuse or my soldering but checking at the wire, before the fuse is was still 4.2v. According to the wiring diagram it goes to the amp gauge, the gauge works but always stays in the negative. What could be causing low voltage on this wire?

Also with the car running and the rpms up checking the volts from the neg ground to the pos post on the alt it will read anywhere from 20-50v but at the battery from pos to neg post its still 12.2, should it be between 13 and 15v?

[JT68]

The large white wire for the alternator (should be) an almost direct connection, through the ammeter and back to the + starter cable ( that little accessory harness at the starter) to the +side of the battery.

You should definitely have the battery voltage present on it when the car is not running. That is likely your problem.

If you only have 4-5 volts at the big white, you have a very poor connection somewhere along the way. There is a multi pin connection above the clutch pedal, the connections at the ammeter, and the connections near the starter. One of those connections is likely corroded/dirty. (Caution, they can get very hot and melt the plastic connectors).
Best, j

[aclever1]

The large white wire for the alternator (should be) an almost direct connection, through the ammeter and back to the + starter cable ( that little accessory harness at the starter) to the +side of the battery.

You should definitely have the battery voltage present on it when the car is not running. That is likely your problem.

If you only have 4-5 volts at the big white, you have a very poor connection somewhere along the way. There is a multi pin connection above the clutch pedal, the connections at the ammeter, and the connections near the starter. One of those connections is likely corroded/dirty. (Caution, they can get very hot and melt the plastic connectors).
Best, j

Thanks I will check all the connections.

[JT68]

Sometimes the ammeter internal connections fail too. Its rare, but happens. Solder fails etc.

If you just need it to charge for verification etc, you can also run the b+ alternator connection straight to the battery + with 10ga wire. In that case the ammeter won't work, but you should get +13-17V when running at 2k rpm or more. An easy test.

Hope this helps

[redroadster]

Yeah ...its not grounding put a redundant ground on it check it by doing a voltage drop test on the base
And do you have a strong magnet on the rotor with the key on ?
Also try a redundant charge wire
Its a 3 wire alt ? The wire to the windings needs to be checked for 12v power

[C.Costine]

Since I have pretty much exactly the same thing going on as you clever1, I thought that I could be clever and jump on here. My wiring which was a little cobbed up when I got the car is pretty well sorted out, with everything in compliance with Curtis's diagrams and everything works except for charging the battery and the fact that the alternator wants to make 25 volts. The alternator is what came in the car, and It was not charging then. I have replaced the ammeter with a voltmeter and have replaced it in the circuit with a fuse, temporarily a 15 amp. At this point I need to know what the alternator is. Can you ID it for me?

IMG_1578.JPG

I measure 0.4 ohms to ground from the case.




.

[Curtis]

Looks like the stock alternator and should be 25 amps. Probably a Hitachi. They have a mark on the back sometimes.

[C.Costine]

Looks like the stock alternator and should be 25 amps. Probably a Hitachi. They have a mark on the back sometimes.

OK, thanks, it has the stock four wire connector to it also. But, it is putting out 25 Volts not amps.

[Curtis]

Looks like the stock alternator and should be 25 amps. Probably a Hitachi. They have a mark on the back sometimes.

OK, thanks, it has the stock four wire connector to it also. But, it is putting out 25 Volts not amps.

Understood. Later alternators are 30 amps and as you well know now 25 volts is well, a problem. Time for the alternator experts to chime in.

[Nissanman]

Lack of voltage regulation. You need to make sure that the alternator output is connected to the external VR correctly.

[Vrosi1963]

I have a 1966 roadster and it has sat for 20 years in a covered carport.it is my brother-in-law's . I bought a new battery and when attempting to get a instrument panel light or starter response from the motor everything is dead. I see 12.8 volts but nothing is happening. are the ignition switches a problem with the contacts corroding ? I have a stock 1943 willys jeep and the technology doesn't seem like much of a step up in technology