Ignition light and Datsun alternator

[Alpine 1789]

I have long suspected that the voltage regulator on my SV was dying. The ammeter needle would frequently jiggle and the headlights would sometimes pulse. Yesterday the ignition light came on while I was driving and stayed on, so I decided that today was finally the day to install the Datsun/Hitachi alternator that I got from Jim E several years ago. Everything went together fine, and I believe I have it wired correctly. The car starts fine and the ammeter reads a steady charge. Jim had put a light in the circuit rather than a resistor. This light seems to work fine (that is, it comes on when the key is turned and goes out when the accelerator is hit) and I understand that the setup won't work without it. However, the original ignition light is still on and glowing steadily.

I haven't yet removed anything from the system (I'll be asking about that shortly) and right now just have some extra wires hanging over the fender. Is the fact that the stock light is staying on anything to worry about? Can I just wire it into the circuit in place of the one Jim had?

Thanks.

 

[Jay Laifman]

I think you have it wired wrong. I have posted on this site how to do it right a number of times. I have the Hitachi/Datsun alternator too. I had to blip the gas to get the light to go out. Then I went to Pep Boys and pulled the Datsun manual with wiring diagram and figured out how to wire it right. It works perfectly now, and has ever since.

There are three connections to the alternator: B, S and L. S gets looped over to B (and this is exactly how it is done in the Datsun too), the B goes to the battery through the connection on the starter solenoid. L goes to the ignition light on the dash - straight there. Now, here is the trick. The OTHER wire to the ignition light on the dash does NOT go to ground. It goes to keyed 12V power.

That's is. All done. Remove all the external voltage regulator and the warning light simulator.

The key to this wiring is that when you first turn the key to start, and the 12V power comes on, it goes into the coils in the alternator and charges the coils. The power also flows through the light and the light goes on. Then when the starter starts spinning the engine and the alternator starts spinning and putting out power, you get power on both sides of the light and it turns off. If you don't do it this way, you don't charge the coils and you need to get the rpms up enough to force charge them.

The Datsun wiring diagram also shows a resistor in parallel with the light. I believe this is so that in the event the light blows, the pre-start charging will still occur. I have not done that. I have an extra bulb.

 

[Alpine 1789]

Thanks, Jay. Apparently, my alternator and yours are slightly different. Mine has three posts too, but they aren't labeled B, S and L. In fact, they aren't really labeled at all. One post is a screw terminal. I am sure that is B. It has what looks like a capacitor on it that is connected to the housing. Below that are two connectors at right angles to each other. Neither of them are labeled. In between the screw post and the two connectors it says BAT, I assume that refers to the screw post.

How can I figure out which is S and which is L?

 

[Wombat]

Jim

The stock light is probably staying on because of the warning light relay. When the Lucas alternator was charging, a little of the current was fed to this relay and it then turned the light off.

You should be able to wire the stock light in place of the additional one you have as per Jay's post.

This link deals with the fitting of a Datsun alternator. May be some help in identifying terminals. If the light goes out and your ammeter is showing charge, the wiring can't be too far wrong. How much do you need to rev the engine to make the light go out?

http://www.team.net/www/rootes/sunbeam/alpine/mk1-5/techtips/altconv.html

 

[Alpine 1789]

Thanks, Robert. Tom's article is the one I used when I originally wired it, but that doesn't appear to be the way Jay did his. However, assuming both methods work, I think all will be fine if I just wire the original light in place of the aftermarket light Jim used. As for how much I had to rev the engine, I am not sure as I only ran it briefly. However, it wasn't much.

 

[Jay Laifman]

R = S. And I do have that same shaped two wire plug in where R and L are. From looking at that diagram, you get the same result. The only difference is that R gets keyed power instead of always having power. While I'd generally think it would be a good idea to have it as keyed power, for the Sunbeam ignition switch, seems to me that less power going through it the better!

Jay

 

[Alpine 1789]

R = S. And I do have that same shaped two wire plug in where R and L are. From looking at that diagram, you get the same result. The only difference is that R gets keyed power instead of always having power. While I'd generally think it would be a good idea to have it as keyed power, for the Sunbeam ignition switch, seems to me that less power going through it the better!

Jay

Sorry, Jay. I think I am a little dense this morning. Which method are you suggesting is better? Yours or Tom's (from the online tech tip)?

 

[Jay Laifman]

I'm saying they are 6 of one half a dozen of the other; but I lean slightly towards mine so that less power is going through the key switch. That's all.

 

[Jay Laifman]

Oh, and I did pick up the plug that fits in the alternator from a junk yard or something.

 

[Alpine 1789]

Thanks, Jay. The car is working great right now, so I think I'll leave well enough alone. Now its time to clean up the engine compartment and take out the parts I no longer need.

BTW: Now that the battery is fully charged, the light now goes out right away.