Second Reman'd Alternator - Still No Charge

[Soup]

RESOLVED: http://forums.hybridz.org/index.php/topic/103159-second-remand-alternator-still-no-charge/page__view__findpost__p__965380

 

Long story short, I picked up a Bosch reman'd alternator and it won't charge the battery. I'm stumped on the what the issue is.

 

I had completed the 280ZX alternator swap into my '73 240Z a few weeks ago with a NAPA special 280ZX alternator, battery read a consistent 14.4V only AFTER I revved the car to 4000 RPM sometime following start-up. At idle, prior to revving the engine, it would be around 12.4V or so. Ammeter gauge would go from the middle (before rev) to about 1/3 into the positive axis after.

 

Thinking the alternator was to blame, I returned it and they gave me a remanufactured Bosch alternator instead. Even worse, this alternator doesn't charge the battery at all. Does anyone know what the issue may be?

 

Car off, battery reads: 12.45V

Car on, idling: 12.18V

Revving the engine up it read 0.01V higher on average

With lights on: 12.06V

 

Could it be that I picked up a second lemon alternator in a row? Or is it something else? When I modified the voltage regulator plug, I followed atlanticz's tech page and it worked well with the NAPA special for the most part, minus the 'rev-to-charge' issue.

 

Help is much appreciated!

Edited November 6, 2011 by Soup

[NewZed]

Pretty sure, if I remember right, that the "L" wire needs power to magnetize the windings in the alternator so it can start producing electricity right away. Yours is probably not connected to power. It's one of the two wires in the T plug at the back of the alt. It would run through the red charge lamp in a 280Z, not sure where it goes in a 240.

 

Search for information on the L or Lamp wire. It might need a resistor or a lamp to avoid damaging the internal regulator. I think it needs a diode also to get the engine to shut off when you turn the key off.

 

 

Edit - maybe you've already done this, but if you search "240z alternator upgrade" on this forum you'll find links to some good write-ups. Either way, it sounds like you should check L for 12 volts, with the key at On and go from there.

Edited November 6, 2011 by NewZed

[Soup]

The car was running fine for the last few weeks until I decided to get off my butt and try to solve the 'mandatory-rev-before-charging' issue with another alternator.

 

I am pretty sure the wiring modifications for the 280 swap were fine - could be an outstanding issue that I've only noticed due to doing the upgrade? At any rate, here are pictures from when I first did this a few weeks ago.

 

Shot of the modified plug from the OEM external voltage regulator:

 

NAPA special 280ZX regulator, charging well after a spirited drive:

[NewZed]

Your first one might have been self-energizing from stray or leaking voltage. I think that the voltage on L should actually be around 2-3 volts, not 12. More will damage the internal regulator. It might be described in the FSM for 78 and on. I'll post it if I find it.

 

I always take electrical measurements after I do wiring mods, so that I know they work correctly. Take a measurement right at the T plug.

 

Edit 2 - Does your charge light go on when the key is On, but before the engine starts? Does it stay on when the alt's not charging?

Edited November 6, 2011 by NewZed

[NewZed]

Found the link I was thinking of. It was for the CS130D GM alternator but I took the measurements on my 76 with a ZX alternator and L voltage was in the range described. The CS130D might be more sensitive than the ZX alternator though.

 

http://www.hotrodlane.cc/ONLINETECH/CS130DREG.html

 

Good luck. Take some measurements.

[Soup]

Thanks so much! Bit of a newbie question but how should I go about measuring the voltage at the L terminal?

 

Should the car be on or off? Unplug the T-connector and place the positive on the L terminal with the negative probe on the case?

[NewZed]

I got curious so went out and rechecked mine. I just put the positive probe in the back of the T plug, still plugged in to the alternator, and grounded the negative. But the rubber on my T plug is rotted away. Yours might be covered. I got 1.7 volts, key On, engine not running.

 

It's not the usual Z car measurement though, I just found the information while working on my own car. You might first just check with the T plug disconnected, with the key On. You should see battery voltage on each terminal individually, positive in the terminal, negative to the case.

 

Back to the the charge light - the charge light can't glow unless current is flowing through the L wire, to and through the alternator. If your charge light doesn't glow when the key is on,the L wire is probably not connected.

 

Also, I found that some alternator winding cores have enough residual magnetism to self-energize. That might be why your old alt charged and the new one doesn't.

[Soup]

My car is a 1973 so no charge idiot light for me. I will check the terminals and report back. Thanks again!

[NewZed]

Page EE-12, 1973 FSM. I think you just gave the critical clue to your problem. The light is there, it's just not connected. Go to the light - and make it shine.

[Soup]

After a bit more searching, I found this thread that describes my exact problem although my 'cut-off' with the NAPA special alternator was at 4000 RPM.

 

http://www.classiczcars.com/forums/archive/index.php/t-35684.html

 

I double checked my modified VReg plug and it is correct. Here are the readings from T-connector on the alternator:

 

With the connector unplugged, key to ON but car not running;

'S' horizontal tab 3.455V

'L' vertical tab 0.00V

 

I yielded the same results with the car running and connector unplugged. With the T-connector plugged in, 'S' read 12.15V while 'L' was still 0.00V.

[Soup]

UPDATE: I checked my modified VReg connector and lo and behold, I had soldered the wrong wires together. On AtlanticZ, I followed the '73 picture and labelled the wires 1 through 6. I then connected them in the sequence that he used for the 280s (1-5 and 2-3). This is wrong.

 

The correct configuration was posted directly below the '73 picture, ironically; black/white to white/black and white to yellow.

 

The FSM is currently downloading so once that is up, I will update on which end of the diode goes to which white/black wire.

 

Went for a quick drive and immediately after start-up, the voltage was 14.15V. Ammeter was 1/3 onto the +ve.

 

Thanks again NewZed!

[Soup]

UPDATE II: There were a couple threads on here that suggested the wrong wiring for a 1973 240Z. For future reference, the VReg connectors should be connected like so:

 

White/Black to black/white

Yellow to white

 

As for the diode, I used a 1N5408 (have 3 extra if anyone needs one and don't want to buy in bulk) diode with the cathode end (end with the WHITE stripe) soldered onto the WHITE/BLACK wire.

 

There weren't many relevant or accurate threads for the '73 240Z so hope this helps!

[mildsquare]

Glad I found this. I've been having to do the "mandatory rev up" for a while. Now I won't sound like a boy racer, every time my car starts. Thanks for posting!!

[3ryce]

I accidentally put the diode in backwards. It was quite funny when the car wouldnt turn off. I even tried to kill it with the clutch. That didnt work. haha. I just followed the picture wire diagram he had up there. Its awesome and works like a charm everytime!