All looks good, but alternator not charging. Help!?

[spider2081]

It was left as stock, so no charge was getting to the positive terminal of the alternator.

That is strange as i would not expect the battery warning light to work properly if the relay was left in the circuit.

I started to post a replay about making sure the relay was bypassed and remembered the statement the light works properly so I never submitted it.
I believe many people fabricate a short jumper wire with a male spade on each end. Remove the battery warning light relay. The bottom of the relay has its terminals numbered. I'm thinking terminals 30 and 85 get jumped together in the now empty relay socket. I believe terminal 30 has a violet/white wire and terminal 85 has a yellow/red wire.
Another approach is to remove those wires from the relay socket and splice them together.
The relay is located under the hood on the driver/left side of the car. It should be the outboard most relay closet to the firewall.
In addition to the 2 wire colors mentioned it should also have a white/black wire on 2 of its terminals that is a chassis ground.

[18Fiatsandcounting]

Maybe one of you wrote this, but I copied some notes from somewhere, as I've been reading up on alternators this past week. Here's what it said regarding going from an external regulator to the modern internal ones (a Bosch unit is used in the example):

"At the alternator all the wires on the original alternator's output post connect to the Bosch output post.
The gray wire connecting the original alternators field to the voltage regulator is not used.
The yellow wire connecting the original alternator to the battery warning light relay gets connected to the Bosch alternator's D+ terminal.

The voltage regulator mounted on the driver’s side fender well is removed and discarded. Make sure all the ground wires under regulators mounting bolts are reconnected and making a good clean ground to the mounting bracket. The gray wires other end was disconnected when the original alternator was removed. The orange wire is powered (12 volts when the ignition switch is turned on. This wire needs to be taped and insulated so it cannot short to anything.

Remove the battery warning light relay. Connect the yellow wire from the (newly installed) Bosch alternator D+ terminal to the black/violet wire for the battery warning light."

-Bryan

[Stookie]

“That is strange as i would not expect the battery warning light to work properly if the relay was left in the circuit.

I started to post a replay about making sure the relay was bypassed and remembered the statement the light works properly so I never submitted it.
I believe many people fabricate a short jumper wire with a male spade on each end. Remove the battery warning light relay. The bottom of the relay has its terminals numbered. I'm thinking terminals 30 and 85 get jumped together in the now empty relay socket. I believe terminal 30 has a violet/white wire and terminal 85 has a yellow/red wire.
Another approach is to remove those wires from the relay socket and splice them together.
The relay is located under the hood on the driver/left side of the car. It should be the outboard most relay closet to the firewall.
In addition to the 2 wire colors mentioned it should also have a white/black wire on 2 of its terminals that is a chassis ground.“


This was the original plan, but what I discovered is that even with those two terminals on the relay temporarily spliced with a paper clip, I wasn’t getting a charge on the yellow/red wire that connects to the alternator. So the alternator wasn’t exciting. Battery charge like was working as normal, but alternator couldn’t be charging without 12v going through this circuit.

I then tested the connection from the relay to the alternator, and got power. Ok good. Then finally, tested from the relay to the back of the key cylinder, no power. So this was the issue. Somewhere in the dash, the purple wire that you splice on the battery relay doesn’t have a good connection. Even if I spliced it as you’re meant to, no power would be getting to the alternator without figuring out where this connection is bad.

So the fix was just to bypass that entirely and connect the 12v from the old voltage regulator straight to the alternator. This works. I suspect the battery charge light will now not operate properly since the charge light relay has been removed from the equation but the system should work just as well as taking 12v from the relay.

I’m instead just going to install a voltmeter to tell me what it’s doing without the need for a multimeter while driving. Should do the same job the light used to do, tell me if the system isn’t charging.

[18Fiatsandcounting]

So the fix was just to bypass that entirely and connect the 12v from the old voltage regulator straight to the alternator. This works. I suspect the battery charge light will now not operate properly since the charge light relay has been removed from the equation but the system should work just as well as taking 12v from the relay.

Stookie, I think you're right. Alternator will charge, but the alternator charge light won't work.

More of Bryan's pontificating follows. Some may wish to skip to the next post.

The "normal" wiring for the internal regulator alternator works by putting 12 volts on one side of the alternator warning light, and the other side is connected through a trio of diodes to the alternator output. Turn on the key, with the engine not running, and the alternator light comes on. When the engine starts, the 12 volts on one side is balanced by 12 volts being produced by the alternator (going through those diodes), and so the current is zero and the light goes out. There is a voltage drop across the diodes of about 0.6 volts, so the battery and alternator voltage don't have to exactly match.

The ingenious thing about this alternator light is that it will glow when the battery voltage is more than the alternator output voltage (bad or weak alternator), but also when the alternator voltage is more than the battery voltage (dead or undercharged battery). Sometimes the light will glow dimly until the alternator and battery are "on the same page."

-Bryan

[Stookie]

I certainly am appreciating it Bryan! Especially with a project/driver level car, I’ve been really happy with the level of understanding I’ve gained of this cars electrical system in only the past week on here. Wouldn’t have had a clue without it, especially since mine has already been modified and I don’t know what stock looks like.

If the car proves to treat me at lest semi well for the remainder of the summer I’m sure I’ll be digging in back there to see if I can make this system work as it should, be another good learning experience . I’ll be keeping the volt gauge though, I was surprised the car didn’t come with one stock in the dash.

[18Fiatsandcounting]

If the car proves to treat me at lest semi well for the remainder of the summer....

The hearing abilities of Fiat spiders are very good, so be careful to only say nice things around the car. God forbid you should drive by in an MG or the like--spiders don't like that. I have a '69 and a '71 parked right to each other, and if I spend too much time on the '69, the '71 starts misbehaving. If I then spend more time on the '71, the '69 starts acting up. It's uncanny!

-Bryan

[spider2081]

I wasn’t getting a charge on the yellow/red wire that connects to the alternator.

I thought I replied to this earlier but I had a phone call and must not have hit "submit"
With the ignition switch in the "on" position grounding the yellow/red wire should make the battery warning light lite. Have you tried that? Have you checked to be sure the bulb for the battery warning light is an incandescent bulb and not an LED?

[aj81spider]

I read this quickly, so apologies if I missed something and am posting completely redundant information. However, it's pretty critical that you remove the old voltage regulator. It sounds like you're making progress on the light and getting the 95 amp alternator to charge, but I didn't see anything about the external regulator (if I missed it apologies again).

Installing the 95 amp alternator on my '74 was actually very easy. The relay and the regulator were easily accessible in the engine bay and rewiring could all be done there. I created a diagram for myself when I did it. I've attached it below. Hopefully it's of some help.

First the stock configuration



Then rewired. The green gets removed, the red was added. The caveat is that this is for my 1974. I'm guessing the '76 is similar, but you should check your wiring diagram to be sure.



Fundamentally it's removing a bunch of stuff and jumpering a couple of wires from the old relay together.

[18Fiatsandcounting]

That's a very handy set of diagrams, A.J., thanks for that.

In a nutshell, the modern alternator's exciter connection changes from the grey wire from the external regulator setup to the "downstream" side of the alternator warning light in the new setup. All else can be disconnected or removed, taking care to insulate any wires that still have +12v on them (like the orange wire to the external regulator).

-Bryan

[Stookie]

Well, finally finished up the project today. Now have a setup where I’ve soldered the old 12v that went into the old voltage regulator and then ran it across the firewall to the positive on the alternator. So, I’ve definitely functionally removed the old regulator! Working a treat, running 14v solid at the battery with headlights and rad fan on. Even did a few short test drives to confirm all is well.

Oddly, the battery charge light still functions...perfectly? I have no idea what’s going on there and I’m inclined not to dig deeper. This make zero sense to me and I’m afraid the answer will open a can of worms I’m not ready for.

Also did a few other small carb tuning touches and it’s Sunday driver ready. Loving it!



One small bit of weirdness though. The autoricambi alternator with their underside mount is causing the alternator pulley to ride about a half inch further back than I’d like. Definitely going to yank that mount back off and see if I can file the back mount down so the alternator can be pushed forward. Should work, just thought it was an odd issue I wasn’t expecting with an aftermarket mount for this application. But, still gotta hand it to the people at autoricambi nonetheless for helping me out over multiple phone calls. Love the support, from you all as well!

[spider2081]

I think the procedure posted by Bryan converting to a Bosch alternator combined with aj81spiders 95 amp alternator wire diagram is the way a 95 amp alternator should be wired in a Fiat Spider. It eliminates both the battery warning light relay and the voltage regulator from the charging circuit. It may not be the only way but its the easiest for future troubleshooting of the charging system.

[18Fiatsandcounting]

Oddly, the battery charge light still functions...perfectly? I have no idea what’s going on there and I’m inclined not to dig deeper. This make zero sense to me and I’m afraid the answer will open a can of worms I’m not ready for.

Stookie, perhaps best to let sleeping dogs lie. But, if you didn't remove/disconnect the relay for the charging warning light, then it might still function if it "senses" when the alternator is running. I don't exactly know how it would do that without seeing how it's wired, but it's possible.

In the original wiring for the early spiders, the relay for this light was driven off of a yellow wire that went to the center of the 3-phase winding of the stator coil of the alternator. When the alternator was working, voltage would be produced, the relay would click "off", and the warning light would go out. If the alternator wasn't charging, the light would stay on. The reason for this arrangement was to put the yellow wire on the side of the alternator diodes where it wouldn't be "fooled" by the battery voltage, and so it was measuring true alternator output voltage and not just the battery voltage.

-Bryan