How many times have I gone done this path, IR Alternator and diodes

[Thomas Dockery]

Once again, we (Matt, Nick and I) find that our Internally Regulated Alternator and wire harness jumper we did some time back is creating a voltage feedback such that the engine will continue to run after ignition switch is turned off.  This use be a dieseling issue but now, with an installed MSD, the engine continues to run.

I seem to recall diode(s) have been used to solve this problem.  Does someone have this info of the top of their heads before I go diving into the DQs?

Tom

[Ronnie Day]

Tom,

Not off the top of my head, but I'd think the process would be the same as on the Roadsters which I'm pretty sure is documented in the Tech Wiki section of 311s.org.

RD

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[paolo]

Tom,

Here is a re-post of something I wrote to this list a while back (9/30/2018).  I may be of some use.

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Tom,

Your friend's suggestions are solid, but depend on the swapped-out alternator.

I have learned over the years that some alternators work best to have a diode on the lamp wire, which is the W/R (White/Red) wire for the Dime, but this has more to do with accurate behavior of the dash pod lamp than parasitic drain.  That circuit is dead when the ignition is off.  I show this on the newer 22x34 poster upgrade diagrams.

Tying the sense line to a switched point is 'sensible' if you can connect to a solid, clean switched wire.  Even then, depending on the alternator's sensitivity, this may have too much of a resistive pathway and cause 'over-sensing' and 'over-charging' as the alternator does not see the most accurate battery voltage.  The regulator should be millivolt sensitive.

If doing this, the best connection point for this that I see would be the L/B (Blue/Black) wire that routes to the ignition switch.  This also means extra wire extension length from the alternator to reach the fuse box.

Again, it depends on the alternator.  A failed or leaking internal diode will cause a drain for any alternator.

There are two types of internal regulators for alternators.  A 'grounded field coil' type or a 'grounded regulator' type.  I don't know if one of these types has a 'leakage' issue, but if one does, I'd assess that the other does not.  I have used later model 810 or 200SX alternators which have demonstrated zero leakage.  I can leave a car for a couple of months with a healthy battery and it will start just fine.  Of course these cars have no fancy stereo or NAV system with a parasitic draw.  There may be a third regulator type for newer cars, which is 'insulated', but I have no knowledge of that.

There are also two types of stator windings: Wye or Delta, but I can't see where that would make a difference.

All a long winded post to say:  I think it comes down to the type or condition of the alternator.  That or an issue with your front harness or ignition switch.  Are all the grounds solid?  Any mods to the dash pod?   

 
Paolo ———

On 9/29/2018 11:56 PM, Thomas Dockery wrote:

Here is how the story and question begins.

Nick's car has ever so small short (if there is such a thing) as witness by a slow, ever present lowering of voltage on the battery as the car sits over night and a persistent arc every time you disconnect the ground cable from the battery.

After disconnecting and reconnecting virtually everything, trying to find something that would stop the arcing, we found the Sense wire coming off of the internally regulated 280ZX alternator would stop the arcing. And with the battery was connected, the sense wire would arc when connecting to the alternator. 

This wire is connected as prescribed in all articles and wiring diagrams, to the white wire that connects back to the alternator power lead, then to the fusible link and of course the constant hot side of the battery (at the starter).  Sorry, stating the obvious for people on this distribution.

On Thursday I met with a friend who works on Datsun/Nissans professionally everyday.  He builds race cars, street cars, old and new.  He told me when that do the ER to IR swap, they always connect the Sense line to Switched not Constant power. If the Sense has constant 12v, it will short through the alternator as it will be trying to energize the alternator when the car is not running.  He also commented that they always add a diode to the Lamp wire, FWIW.

And FWIW, we have tried three different, new/rebuild alternator and have replaced the battery twice.

What have you guys think?

Tom

***********************************************

Paolo ———

[Thomas Dockery]

Thanks Paolo,

It's funny that the problem I wrote about back in 2018 may be the same problem that has never gone away. 

As I recall, we have tried several alternators over the years, mostly 280ZX rebuilds, I think.  One of the problems we had with these alternators were their size ..... they barely fit in the space available.

What alternatives are others using? Any direct bolt ins that are still available as New units?

Tom

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Sent: Wednesday, April 21, 2021 7:41 PM
To: blueb...@googlegroups.com <blueb...@googlegroups.com>
Subject: Re: [Bluebird510] How many times have I gone done this path, IR Alternator and diodes

 

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[paolo]

Tom,

1. I was short on time yesterday but remembered the 2018 discussion and quickly re-posted it.  Since that post, I have retrofitted a few Dimes with LEDs throughout - interior and exterior (sans headlamps) and found the 'charge' lamp to be finicky.  Using a diode on the R/W wire (or LED lamp) can present a problem for Datsun alternators.  First, an LED also does not allow enough current.  Second, current needs to flow both ways. 

The lamp serves as an indicator for malfunctioning alternator when engine is running but it also allows a small current at some voltage to at start-up to energize (or excite) the alternator's field coils to generate electricity.  Once energized, they stay energized until shut off for a while.  When a 'charge' lamp was burned out, the older style Datsun alternator could usually be initially energized by 'gunning' the engine for a burst, but not a good way to get by.  Thus I don't recommend a diode on the lamp wire.

2. I don't think the problem is with the alternator connection (either lamp or sense wires).  The ignition switch or alternator are more likely culprits. Very remote chance for leak in hazard switch.  Have you tried unplugging the alternator Tee connection and tested for voltage or ground where either shouldn't be?  I assume you no longer have the either original external regulator or choke relay connected?

3. If memory serves, and 60-amps is OK, the last alternator I bought that fit well and was smallest I could find was a reman for a 1st gen Altima.  I recall just little bit of modification was needed to fit just right.  All the other 60-A alternators from the 6-cylinder Datsuns were too large to have any useful adjustability and needed mods.  BTW, I always remove the mount, drill it out for a single larger pass-through bolt.  It seems I've also done a bit of grinding on the mounts to get the larger units to swing closer to engine.  Not sure if that was needed for the Altima unit.

Paolo ———

/BYAPR20MB26964CF6189340463F3B6371CD469%40BYAPR20MB2696.namprd20.prod.outlook.com.

[Thomas Dockery]

Quick update, for the record.  Setting the background, we are running an L18, A87 JDM SSS engine.  It was recently rebuilt by Rebello (head gasket failure brought on but water damaged cooling port in the head).  Distributor is a Cardone 31-620, unit with internal (as opposed to external, matchbox style) electronics. This distributor will not work without some sort of ignition control module.  In our case we installed an MSD 6AL.  

We saw significant improvement the both startup, timing and idle stability but the car had this run-on problem after the ignition was switched off.  We replaced the IR alternator with a newer rebuild from a VG30 (84 300ZX).  This unit is a 70-amp unit fits nicely on the standard alternator bracket.  It is a smaller form factor which is nice too.  This unit doesn't use the classic T connector but this is easily resolved.  Our thought was this alternator might have an internal diode circuit which would eliminate the stray voltage which kept the engine alive.  Unfortunately, it didn't solve the problem.

MSD installation manual says run-on is not uncommon on older, externally regulated cars (we are running an external regulated alternator but still and interesting note).  MSD's suggestion for this issue is to insert a diode on the charge light wire as it exits the alternator.  We added a 6amp diode as described by MSD and the run-on was eliminated.

The next step is to figure out how best to reconnect the factory tach with this set up ....... we will probably look at MSD's Magnetic Trigger Connector (8920) for tachometers.

Tom

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[Dan Heil]

Electric Fan? 

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Dan 
1987 Yamaha 250SRX
And  510 wagons!

[Brock Johnson]

Am I reading this correctly? You are running an externally regulated alternator?

If so, is there a reason why you haven't converted to internally regulated?

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Rear Wheel Drive, the way God intended.
If a car is being pulled from the front, doesn't that mean it's being towed?

I can explain it to you, but I can't understand it for you.

[Ted Hedman]

Can you disconnect the alternator, and with car running on battery only, switch off the ignition to rule out the alternator and charging circuit as the cause of the no stop condition (or not)?

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[paolo]

Me too.  I'm confused.  External regulator for an '84 car?

AFAIK, Nissan stopped making externally regulated alternator somewhere in the mid to late 70's.  Or at least any vehicle with EFI should not have one.  How stock is the engine and cabin harness?  All bets are off if you have lots of custom work. 

Still, I bet it's all in the MSD wiring changes.  I've never run an MSD so I can't help here.  Any links to the MSD wiring needs?

Paolo ———

[Thomas Dockery]

Let me try again. Our car is internally regulated. The MSD manual notes the Run-on is not unusual on externally regulated alternators/cars and suggests the diode. 

We decided to try the diode anyway, on our internally regulated alternator/car and it solved the problem.

Tom

Sent from my iPhone

On Apr 23, 2021, at 2:14 PM, paolo <pa...@cedarcomm.com> wrote:



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[Thomas Dockery]

And in case this was also a point of confusion, this a 1969 510 sedan which has had a 71 dash and harness conversion. The alternator now in place with the diode is a 1984, 300ZX, internally regulated (of course).

Tom

Sent from my iPhone

On Apr 23, 2021, at 2:28 PM, Thomas Dockery <drive...@msn.com> wrote:

 Let me try again. Our car is internally regulated. The MSD manual notes the Run-on is not unusual on externally regulated alternators/cars and suggests the diode. 

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[Brock Johnson]

OK, just a typo then.. Back to the previously scheduled discussion.

MSD installation manual says run-on is not uncommon on older, externally regulated cars (we are running an external regulated alternator but still and interesting note). 

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[Cody Mould]

Hey Tom, I ran into this with my VG30E swap as well. A diode on the charge light wire was enough to interrupt the electrical flow that kept things running. The alternator would feed just enough power through the charge lamp to keep the relays energized... It was crazy. Here is some snippets from my facebook page on this topic.

*SOLVED*

*** Alright folks, between this post and another one I had on a different page it was revealed that alternator feedback through the charge lamp circuit was reenergizing the ignition-on side of my ignition switch and thus holding the relays for EFI computer and fuel pump closed. a local Datsun guy who deals in electronics gave me a one amp 50 V diode , which I wired in with the silver and facing towards the alternator. They are incredibly fragile as are the connections to the wires so I sleeved it inside a cutdown Bic ballpoint pen tube for protection. now everything functions as it should and the engine cuts out immediately . Figured I would follow up on this in case anyone else had any issues like this!***

Hey all, anyone with a "modern swap", could be anything really, I'm having an issue where turning the key off isn't always a guarantee of the engine actually shutting off... It can continue running for seconds, or indefinitely, at random. If I unplug the alternator connector, everything behaves fine.

Somehow my b/w wire gets energized with roughly 5V when turning the engine off....

http://woodworkerb.com/home/datsun-240z-rebuild/datsun-240z-alternator-upgrade/