10 SI alternator & engine keeps running

[Godwin]

When I bought my FJ40 a Delco 10-SI alternator was already installed, and things have been working fine for years. Today the alternator died so I replaced it with a remanned 10-SI unit. The problem that has cropped up with the new alternator is that the engine (a 2F) will not shut off when the ignition is turned off. The alternators are of the same type so this is a bit of surprise.

Now how to rectify the problem?

Do I need to intall a diode into one of the wires, and if so, which one? With the spade connection the upper wire is white and maybe 14 gauge while the lower is red and maybe 12 gauge.

Would swapping the position of the white and red wires do the trick?

 

[lone gunman]

boy i dont know ? but check out www.alternatorparts.com they have wiring info maybe it will be helpfull. good luck!

 

[Mark W]

Your alternator is backfeeding and energizing your ignition circuit. Even if you cut the supply at the key, the alternator and the ignition are on the same side of the switch so everything keeps on humming along.

Simple fix is to energize your alternator with the accesory circuit. This isolates it from the ignition circuit and when you switch off the key the engine obeys.

I have heard that wiring it this way *can* cause voltage spikes in the alternator which *can* damage it. I have and am still running several rigs this way with total usage time of 15-20 years between them all. No problems so far.


Mark...

 

[Godwin]

Simple fix is to energize your alternator with the accesory circuit. This isolates it from the ignition circuit and when you switch off the key the engine obeys.


The engine continues to be disobedient Here's a pic of the wiring. It was set up in this manner when I bought the 40, worked with the old alternator but not the new. White wire with a stripe routes back into the harness to the + on the battery; white wire on side routes back into the harness and is switched with the ignition, red wire goes directly to + on the battery (and seems to be the culprit). What I have tried so far:

Insert diode between + and red wire. If the diode is placed in one direction there is no change with shutting off engine. With the diode position reversed the engine will shut off with the key, but the alternator is not charging based on voltmeter reading (I have an aftermarket voltmeter installed).

I have also connected the red wire to a 12 v switched source with no change in operation, ie. the engine continues to run with the key switched off.

I've also read old posts and the alternatorparts and madelectric sites. I'm easily stumped with electrical issues so I could use some real guidance here.

What can I do to correct this little glitch?

 

[ranger]

Need to run a diode to keep the engine from run on.
See here. http://www.madelectrical.com/catalog/alt-1.shtml

 

[theo]

The wiring is correct. As far as I know, the diode goes in the white, switched wire. Or you could follow Marks advice since he makes a living at this kind of thing.

As a side note, I was running a 12SI that I reconditioned - new brushes, bearings, regulator, and diode trio, and larger windings. It worked fine. I reconditioned a 2nd 12SI for a spare but I don't remember if I replaced the diode trio and/or the regulator. The engine wouldn't shut off with that 2nd one installed!

Have since moved on to a different engine so I never tracked it down.

 

[Godwin]

Thanks for the feedback. I have not tried the diode in the white switched wire because of the need to cut into it and didn't have time for that this morning (but I did consider it). This will be my next step.

 

[Mark W]

Red wire to the battery is not right. It can create a constant drain on the battery. This is probably (almost certainly) how the battery if backfeeding the ignition (power from the batter via the red wire, through the alternator and out via the white wire When you hooked the red wire up to switched 12V was it switched by the ignition circuit or the accessory circuit? Make sure it is accessory. Then if it still runs on after shutoff, switch the two wires on the side of the alternator.

If you are not having a battery drain issue with the red wire going direct to the battery, you can probably solve the problem with a diode in the white wire. This will let power from the switch reach the alternator but will not let power flow back the other way an energize the ignition when the key is turned off.


Mark...

 

[1Fine40]

I have your exact same set up. The diode was the solution. Inline in the white wire, stripe on the diode (cathode side) goes toward the switch, not the alternator. Has been huming along for years that way..I'm upgrading to a higher amperage 12SI shortly, and I hope it will still work o.k. then.

Cheers!

 

[pbgbottle]

heres a quick guide .doesn't it also have to do with a missing dummy light ?

http://www.oldengine.org/unfaq/10si.htm

tons of info here about 10Si ,12 Si and voltage sensing wire

http://www.madelectrical.com/electricaltech/delcoremy.shtml

 

[theo]

Red wire to the battery is not right. ...

This is the voltage sensing wire and is designed to be connected to +12V. You can connect it to the battery or to any other "hot" terminal, depending on how much voltage drop you have in the system and where you feel the best place is to detect it. Works fine connected to the battery for lots of people.

ps - Mark, I think I was thinking of a different Mark when I said ". . . follow Mark's advice since he makes a living . . ." No offense.

 

[nat]

Instead of a diode, hook the white wire into your charge light, it accomplishes the same thing.


wiring goes like this:

acc pwr to charge light to white wire.

red wire to battery or to a power distribution post

wire on back of alternator to battery or power distribution post.

 

[Godwin]

Got it.

I placed a diode in the white wire and that did the trick. Thanks for everyone's help.

 

[ranger]

Excellent!

 

[Mark W]

This is the voltage sensing wire and is designed to be connected to +12V. You can connect it to the battery or to any other "hot" terminal, depending on how much voltage drop you have in the system and where you feel the best place is to detect it. Works fine connected to the battery for lots of people.

ps - Mark, I think I was thinking of a different Mark when I said ". . . follow Mark's advice since he makes a living . . ." No offense.

You can get lucky and run the sensing wire straight to the battery. But this is not consistantly workable from alternator to alternator. Many will give you a constant path to ground and a constant drain on the battery if you do not run it through the ignition switch.

Not sure which Mark you were thinking of, but I certainly didn't take offense. I too make a pretty good living at this stuff.


Mark...

 

[FJBen]

I know this is old...but what value of "diode" is everyone running inline...

If I were to go to an electronics store/auto wherever...what value/size of diode should I ask for?

 

[1Fine40]

I know this is old...but what value of "diode" is everyone running inline...

If I were to go to an electronics store/auto wherever...what value/size of diode should I ask for?

I used a 1N4001 diode.....for whatever that is worth, it is still functional!

Cheers!

 

[FJBen]

I used a 1N4001 diode.....for whatever that is worth, it is still functional!

Cheers!

awesome...thank you much sir!

 

[Fuzzy Logic]

I went through the same, here is the thread--- https://forum.ih8mud.com/showthread.php?t=116504 diode pt# 1n5404 from radio shack

 

[Plowboy]

Different twist to the question. I have never run the two wires to the plug in the alternator, only the white/blue strip to the + on the alt. Takes a few rpm's to get the alt excited but works fine after that. Am I missing something, or just been lucky for the last ten years?