KA swap 510 alternator question

[JSmittyBMF]

Hello all. I'm finishing up my 69 510 KA24DE (1994 240sx) swap and I'm having an issue still. First, thank you guys so much for all of the help. I've treated this website like my own personal shop manual and I've found multiple answers to other problems I've had. The car starts and drives great now. With the knowledge from this site, and personal help from some members (looking at you @the510keeper), I have a pretty fun 2 door almost ready to go.

 

the problem: It's not charging. The car has the stock 240sx engine harness and ecu with an aftermarket everything else harness (not stock 510 wiring). I've only ever done GM 1 wire cause, well, it's 1 wire. question is, how do I get this thing to charge? I've read tons of old threads that either have broken links to wiring diagrams or ones I don't want to necro with a question. Does anybody have a diagram of how to wire this? There's a solid white wire (i have it hooked to 12v+), a B+ post (also on 12v+) and this smaller white/red wire that I can't figure out. I read its for a dummy light. Is it a negative dummy lead? Positive? If I yell at it will it start working? Is it wired correctly so far? I only get access to the car for about 3 hours every weekend cause the car is in a friends shop. Gotta get in where I fit in lol. Thanks yall

[ggzilla]

The stock 240SX alternator is a 2-wire. The L wire must be connected to the 510 dash light, the S wire to the battery

[JSmittyBMF]

14 minutes ago, ggzilla said:

The stock 240SX alternator is a 2-wire. The L wire must be connected to the 510 dash light, the S wire to the battery

Now when you say L wire...wut. lol. What color is the L wire? What dash light? Can I just hook up any 12v light? Is it the negative or the positive side? I'm assuming the "L" wire is the smaller white/red wire. 

[ggzilla]

The back of the alternator has an oval shape connector. Right on the alternator case it is marked "L" and "S". The L wire my notes say is white/red for the 240SX

 

The alternator light is in the 510 dashboard cluster. It said IGN on my 1969. Newer ones I think it says CHG

There is a wire that goes from the dash out to the engine harness, i think it is also White/Red stripe

 

Oh, and like the GM alternator, it needs a dedicated ground wire to prevent problems later down the road

[JSmittyBMF]

8 hours ago, ggzilla said:

The back of the alternator has an oval shape connector. Right on the alternator case it is marked "L" and "S". The L wire my notes say is white/red for the 240SX

 

The alternator light is in the 510 dashboard cluster. It said IGN on my 1969. Newer ones I think it says CHG

There is a wire that goes from the dash out to the engine harness, i think it is also White/Red stripe

 

Oh, and like the GM alternator, it needs a dedicated ground wire to prevent problems later down the road

Thanks for the info. I don't have the stock 510 wiring. My question was more trying to find out what the wire wants or is. I'm not really asking specifically what to do for my application because every application will not be the same. I don't have a dash light nor wiring harness. That's why I was asking the way I was.

[ggzilla]

I haven't thought about that because every Datsun has the dash CHG warning light , even those with a factory voltage meter. I think it needs switched 12V but can't remember if it needs some resistance. I don't recall anyone ever asking that question in the last 20 years, but it is a good question

[JSmittyBMF]

 

11 hours ago, ggzilla said:

I haven't thought about that because every Datsun has the dash CHG warning light , even those with a factory voltage meter. I think it needs switched 12V but can't remember if it needs some resistance. I don't recall anyone ever asking that question in the last 20 years, but it is a good question

That's what I was thinking. I hooked up a 12v light to it using the small white/red as ground and the pos of the led to 12v+ but it still didn't charge. The led didn't turn on at all. Maybe it needs to be on the starting circuit instead of the 12v+ constant. Like the alternator has to spin AND immediately get 12v or something. I'll give it a try next time I'm at the vehicle. or I guess I'm putting the old cluster back in 😆 

[ggzilla]

LED only works one way. Reverse the leads and try it again, I'm curious to see is that's all it takes

 

The alternator L (lamp) wire provides the ground for the CHG bulb, even when alternator is not turning. Then, once it spins fast enough to put out battery voltage, then the bulb has 12V on both wires, so the light goes out

[JSmittyBMF]

20 hours ago, ggzilla said:

LED only works one way. Reverse the leads and try it again, I'm curious to see is that's all it takes

 

The alternator L (lamp) wire provides the ground for the CHG bulb, even when alternator is not turning. Then, once it spins fast enough to put out battery voltage, then the bulb has 12V on both wires, so the light goes out

Interesting. I wonder why the LED didn't turn on when it was hooked up then. Unfortunately the car isn't at my house otherwise id be trying everything. It's one of a few problems I'm having with the swap. The other is fuel related. pretty sure the regulator is bad. 

[ggzilla]

When an LED is hooked up, the positive lead is to +12, the other to ground

If you have it the other way round, it won't light up

 

The alternator L wire acts as ground wire when not spinning. Once charging, the L wire is +14 volts. But the lamp gets the charging going: if the lamp don't light up before you start the engine, the alternator will never start charging

 

[JSmittyBMF]

16 hours ago, ggzilla said:

When an LED is hooked up, the positive lead is to +12, the other to ground

If you have it the other way round, it won't light up

 

The alternator L wire acts as ground wire when not spinning. Once charging, the L wire is +14 volts. But the lamp gets the charging going: if the lamp don't light up before you start the engine, the alternator will never start charging

 

I would love to completely ignore this thread now but for the sake of future readers I will post what fixed it. Turns out I put the positive of the led on the solenoid like an idiot. So yeah. Once the led was on the starter constant 12v it all started working. I understand doing it this way will drain the battery but this is only to get the car home. I will probably wire the led to keyed 12v in the future.

 

As far as the fuel issue, regulator was fine. I pulled the fuel rail and none of the injectors were firing while cranking. I cut the orange start signal wire and they started squirting. Now to start the car and have to have the throttle a little bit open to trick the computer and add more fuel. So now it starts and charges. I'll figure out the actual fuel issue some other time.

 

Thanks for the help

[JSmittyBMF]

one more thing to add. The LED I was using apparently doesn't have enough resistance to trigger charging. So I only have 1 reverse light going home lol.