S30 260Z Charging System Problems

[z-ya]

Hello All,

 

I recently picked up a early 74' 260Z with 25k miles on it for free. It is all original, and still has the CT plates from 92'. Has some minor rust problems and lots of mouse droppings. Also has uncracked dash and besides the seats, a perfect interior. I've got it running pretty good now, but am struggling with the charging system.

 

So far I have tried the following:

 

- Three different voltage regulators

- Cleaned all connectors

- Tested alternator, and is fully functional

- Checked and cleaned fused links

 

The battery voltage is around 12.6V, and doesn't vary mutch when I change engine RPM.

 

Any suggestions appreciated.

 

Thanks,

 

Pete

 

[Captain Obvious]

I (like you) would like to see the voltage go up as you raised the RPM, but I'm not sure what else you could check. There just isn't much to the system. Couple questions I guess, just to get some ideas moving maybe?

 

You said you tested the alternator and it's fully functional... How did you test it?

Maybe the alternator is doing it's best to charge a bad battery that's sucking down the current? Are you sure the battery is in top shape?
What does the ammeter indicate? Is it showing the battery is charging?

 

All else fails, I'd get out from under it before it becomes more trouble than it's worth. I'd be happy to take that 25K mile uncharging burden off your shoulders. 
 

[z-ya]

Thanks for the reply.

 

I tested the alternator by connecting the battery + terminal to the  input voltage pin on the two prong alternator connector. This is what the FSM says. The RPM dropped, and the battery voltage started rising. The dashboard ammeter started deflecting. With things connected normally, the dash ammeter needle never deflects in either direction.

 

I don't give up easy . Going on my 4th S30. First 260Z. Besides the smell, I kind of like it. Keeping it as stock as possible.

 

[Kurbycar32]

i second the captains suggestion about using a known good battery.  I've been in this situation twice and both times a good battery fixed the problem.  Borrow one from a working car 

[Zed Head]

 

I tested the alternator by connecting the battery + terminal to the  input voltage pin on the two prong alternator connector. This is what the FSM says. The RPM dropped, and the battery voltage started rising. The dashboard ammeter started deflecting. With things connected normally, the dash ammeter needle never deflects in either direction.

 

 

I think that this would normally be a sign of a bad regulator.  The regulator is supposed to do what you did.  Since you've tried three regulators though, the problem might be in the wiring to and from the regulator.  With the wiring diagram you should be able to check each wire's connection and continuity.

[Captain Obvious]

I took a quick look through the FSM and didn't find that alternator test procedure. Only thing I found was a test on EE-19 (74 FSM) and it didn't test what you did. Not saying what you did isn't a good test, but I couldn't find that description.

 

So does your CHARGE warning lamp light up when you turn the key to ON before you crank the engine? And what does the CHARGE lamp do once the engine is running?

 

Reason I ask is that while the alternator really doesn't need the charge lamp to be functional in order to work properly, the operation of the lamp can provide some insight into the health and operation of the voltage regulator.

 

Keeping a 74 stock? Cool. You better still be running the flat top carbs!

 

(Edited for the external regulator operation)

Edited November 14, 2014 by Captain Obvious

[z-ya]

OK, found the issue. I check the continuity of the entire circuit, and it was OK. Then I went back and tested the spare voltage regulators I had tested before. I noticed that one had corrosion I had missed. Cleaned it up, and that regulator worked. So it's chaging now! Took it for a spin around the block last night, and besides the lumpy 20+ year old tires, and ran and drove pretty good!

 

Here is the alternator test. Basically if the voltage rises at the battery, the alternator is good:

 

 

[Captain Obvious]

Excellent. Another crisis averted!!

 

Yeah, that's the same alternator test I was looking at in the manuals. What's got me is that the text instructions seem to be in disagreement with the test wiring diagram. I know what they were trying to accomplish, but I don't think the translation turned out very well. Glad you made more sense of it than I did!

 

Glad you got it figured out, and if something insurmountable comes up, remember my offer to lighten your burden. 

 

BTW - Are you sure it's 25K miles and not 125K?

[z-ya]

I can't be 100% sure, but the brother of the second owner who gave it to me thought that it didn't have a lot of miles on it. The oil in the engine, looks like it just came out of the bottle. Under the cam cover it is incredibly clean. The transmission shifts like new. It has the original OEM muffler on it. The clutch pedal does have some wear though. Threre are no drive line clunks. The plates say 1992, but the safety inspection sticker is from 1985.

[Freez74]

Nice car, I have one very similar, love to see more pics.

[Captain Obvious]

Regardless of 25 or 125, it sounds like a great starting point and I hope you have a great time with it!

 

Out of curiosity, are you running the flat top carbs or has someone done a round top conversion some time in the past?

[z-ya]

It has the flat tops, so we will see if I can get it running good enough without doing the swap. If I end up making it a driver, then I will probably swap over to round tops. In either case I will save all the original parts.