[SixBanger]

(this is for a '73 240z)

I just did the IR alternator swap (the second time), and i finally got the overvoltage problem fixed. Surprisingly, the first alternator i had had a broken voltage regulator, and i was scratching my head for answers the past couple months. In goes a new alternator, and viola! no more voltage problems.

Now on to the problem... i turn my car on and it runs fine the entire time with no voltage problems, but when i go to shut it off, it keeps running. I hear the relay under the glove box click as usual, so the car should shut off, but it doesnt! All the accessories keep working and the car just keeps idling, long after i have turned the key and pulled it out of the ignition. I heard about a problem like this, and something about installing a diode, are these the symptoms im experiencing? Please if anyone could help me out I'd appreciate it.

 

[shaver]

Re: internally regulated alternator swap, car keep

You are getting a voltage feed back from your regulator shunt. Try disconecting it. All the shunt does is get your altenator to charge right away, but without it you just have to rev the engine to 2500 or 3000rpm and it will kick the charging right in.

 

[SixBanger]

couple questions

where is the regulator shunt, and isn't there a healthier solution to this besides reving the crap out of my motor the second I turn it on, scraping the unoiled cylinders and causing major wear and tear?

 

[Adam_260z]

Re: couple questions

I don't know where the shunt is, but your car will run a LONG time on just the battery (I drove from Mt. Shasta to Sacramento with a dead alternator, but that was a simpler car). Don't worry about revving to 2500RPM right away.

 

[JeffK]

Re: couple questions

You need to put a diode in series with the "L" terminal. Search th archives for "diode" for more info.
JeffK

 

[71240L28]

Here's how I fixed mine

I had this problem and thought I'd share the solution. Many thanks to Ken Osman and
Steve Golik who provided the solution:

When an internally regulated alternator is put into an early Z and the external regulator is
removed, you often have the problem that the car will not shut off when the key is turned off.
You have to put a diode in series on the wire that goes to the "L" terminal on the back of the
alternator. The "L" terminal is the bottom contact on the "T" shaped connector. You have to
connect the cathode of the diode (identified by a stripe on that end of the diode) to the "L"
terminal and the anode (other end of the diode) to the wire that previously went to the "L"
terminal. In my case (71 240Z) this was a white with black stripe wire. This prevents the "L"
terminal current from feeding back into the ignition circuit when the key is turned off. The
diode I used was a 1N5402, other people have used a 1N5400 or a 1N5062. Easy fix to a
vexing problem.

 

[frogdog]

Re: Here's how I fixed mine

I had exactly the same problem. After I installed a 280ZX, 1983 engine in my 72 240Z I wanted to use the later model alternator with internal regulator. I asked for help on zczar.com but no one came forward with the solution. I then remembered I had read how to do it a few months before and had printed it out for later reference. I believe it was Steve Golik of Smoky Mountain z car club that wrote the answer to the swap. I did as he explained and it worked as it should but the engine would not turn off.
Where did you get the DIODE and how and/or where did you install it? I removed the old regulator and connected the white and yellow wire together and the white with black stripe to the black with white stripe together, from the engine wireing harness. I used a reglator connector and used jumpers in it then just plugged it back on the engine harness connector.

 

[71240L28]

Re: Here's how I fixed mine

I got one from where I work (5 finger discount). Radio shack lists them on their website but the local store didn't have any. You could order it from the website, I think. If you have an electronics repair shop or auto electrical shop in your town they might have one or know where to get one.

As far as where/how I installed it, re-read my last post and ask me a specific question if it's not clear. I did it a while ago so I may not remember exactly but it was pretty straightforward. I got some info from Steve Goliks write-up on (I think) zdriver.com. Let me know if you get stuck and I'll look at my car and help you if I can.