1 wire alternator install problem.

[nismou20]

There should be 12vdc at positive lug on Alt with engine off. Is 30 amp fuse good? Do you have an open in that 10amp wire?

[mraitch]

@aclever1 - have you looked at the techwiki??

[aclever1]

I did read the wiki and anything I could find here. It seemed pretty straight forward only a couple of wires but there isn't anything there for trouble shooting. It is wired as per the instructions but something else is going on.

I just went and checked again, my front right turn signal wasn't working, it would light up just not flash and the indicator doesn't flash on that side either so i cleaned all connections and changed both bulbs and that didn't fix it. the flasher clicks but at a different speed for the side that sin't working.

While I was doing that I tested the voltage from the alt to the ground and it was 10v so I started the car. It stayed at 10 until I reved it and it went to 17.5v so I turned off the car and it went down to 3.5v so I think we have another electrical issue going on. My horn is unhooked, I have that turn signal problem so maybe I will get that sorted out first. I hate electrical, thanks for your guy's help.

[mraitch]

which side have you installed it on??

[JT68]

I hooked a wire from the alt #1 to the black/white wire that went to the regulator and It might have been working, amp gauge was at 0 when running but dropped to about -5 when lights were on but when I turned the key off the car continued to run.

Doesnt sound like it is wired correctly or charging.

Sorry, I assumed a one-wire mini denso. Is this a GM alternator? I really doubt this is a ground issue since the alternator is bolted to the block in two places. Typically, it will be pretty well connected to ground. But yes, a separate ground wire is recommended. If you have an ohm-meter, you will read about 1 ohms etc between alternator case&ground if well grounded.

Yes, a true one-wire configured gm SHOULD work with only the big white wire to the ammeter connected AND should swing well positive after starting and a blip of the throttle.

Sounds like it is NOT a one wire, but rather a 3-wire internally regulated unit. In that case, you need to connect the "Voltage sensing wire" to either the big white wire (sharing the B+ terminal on the alternator) or run the sensing wire directly to the battery+ terminal. You also need a connection to the idiot light L connection with either a lamp, resistor and/or diode, to switched 12+ (that regulator connection again). Otherwise, it won't charge and/or you will have a run-on problem.

If you don't understand any of what I'm recommending, you might want to get an auto-electric shop to help you.

Hope this helps/j

[aclever1]

which side have you installed it on??

Its on the right passenger side.

[aclever1]

I hooked a wire from the alt #1 to the black/white wire that went to the regulator and It might have been working, amp gauge was at 0 when running but dropped to about -5 when lights were on but when I turned the key off the car continued to run.

Doesnt sound like it is wired correctly or charging.

Sorry, I assumed a one-wire mini denso. Is this a GM alternator? I really doubt this is a ground issue since the alternator is bolted to the block in two places. Typically, it will be pretty well connected to ground. But yes, a separate ground wire is recommended. If you have an ohm-meter, you will read about 1 ohms etc between alternator case&ground if well grounded.

Yes, a true one-wire configured gm SHOULD work with only the big white wire to the ammeter connected AND should swing well positive after starting and a blip of the throttle.

Sounds like it is NOT a one wire, but rather a 3-wire internally regulated unit. In that case, you need to connect the "Voltage sensing wire" to either the big white wire (sharing the B+ terminal on the alternator) or run the sensing wire directly to the battery+ terminal. You also need a connection to the idiot light L connection with either a lamp, resistor and/or diode, to switched 12+ (that regulator connection again). Otherwise, it won't charge and/or you will have a run-on problem.

If you don't understand any of what I'm recommending, you might want to get an auto-electric shop to help you.

Hope this helps/j

What kind of diode or size of resister do I need? I don't have any diodes and it might take some time to track one down but for the idiot light can I just wire in any 12v light bulb?

[JT68]

Yes, you could use any small 12v bulb, instrument lamp etc. It is only on when the key is on, engine off. An LED might work too-seems like it would, but I've never verified it. Can be used as an under the hood light-hah.
I believe typically an 80-100 ohm resistor is called for- a few watts most likely.

[Lorna c]

I had fun like this too . start with fuse panel wiring . make sure they're in line with what's supposed to be and match up with what wire should be on its other side . if they're messed up itll fix most if not all your problems . then get familiar with the blinker and light connections in trunk brake lights and headlights . a flip of wire can make for some fun hunting . I say start with fuse panel because if it's not right first , then you're waiting your time on everything else. ya know. removing , cleaning and putting back can mix up the wires if someone previously didn't pay attention when doing this . and in 50yrs time that may have happened . be patient . electric is simple . follow the roadmap is all . good luck.

[JT68]

The charging system can also be connected in such a way that it really doesn't need much of the harness at all to be functional
-might be a good idea if your harness is a mess. Correct the charging issue-then address horns, blinkers etc separately.

If this is a 3-wire GM you can simply route the big B+ connection AND the alternator sense connection directly to the battery + terminal, then the only wire you need from the harness is the ignition on wire (black/white) to power the lamp circuit. You would also need to cut/insulate (well) the original white alternator wire so it can never touch the chassis.-no longer used.

Of course, the alternator still needs a secure low resistance ground.

This is pretty much how GM wires them - there is no harm. If wired this way, the charging system will charge if the engine runs, the harness is otherwise out of the picture.

In the roadster you would have no indication of charging except the idiot light would not be lit when running-just like gm.
IN THIS CASE THE DASH AMMETER WOULD ONLY SHOW NEGATIVE- never positive, charging or not! You could check the battery voltage with a meter and with the engine at 2K rpm, the voltage will be over 12. If you want to be fancy, install an under the dash voltmeter. You would also see headlights brighten whenever the alternator kicks in.

This might be a good setup/method for Linda's roadster too, since other than ignition ON, it bypasses the entire roadster harness. Not unique to the GM alternator, most alternators can be wired this way too.

[redroadster]

New alternator right ? Some the brushes are just flat cut and barely contact the commemtator , they soon will more and more ,back in the 70s they all were. And had a lite varnish to keep moisture from it

[JT68]

I think he said two new alternators - most likely a connection/wiring method problem.

One could also make the "idiot light" circuit more useful - use it for underdash lighting with a low watt/bright bulb or even power a relay for more wattage hah! Certainly would work if done properly.

Could be done with any alternator with an L circuit-even an original alternator//

[Curtis]

You should read this.

http://www.madelectrical.com/electrical ... wire.shtml

[aclever1]

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.

[Curtis]

Low windshield 1600 cars are so easy to deal with. We don't need all the brackets and the wiring is easy. Yup, you would have been far ahead with JT's kit.

Diode 1N5402 works. My experience with an idiot light required a resistor inline to make it work. The guy had me use the S brake light.