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

[Stookie]

Hi everyone, just bought a 76 spider last week and having a very confusing issue. Essentially, car seems to be well sorted from most all perspectives. Drove it three hours home after purchase with no issue.

But, since getting it home, I’ve found that the charging system is not working. I’ve done a lot of research here before posting this but I’m running out of ideas. Essentially...

Found that the alternator was the autoricambi 95 amp. Tested 12.5 at the new battery I put in, tested 12.5 at the alternator with the car off. Car on, battery drops to 11.5 and falls, alternator reads at 11.5. So, it isn’t charging. Take it off, have it bench tested, bench test says it’s bad making only 10.5 volts. Ok fine.

Get a new autoricambi 95 amp yesterday, put that in, and reading across the board are exactly the same. My charge light in the dash comes on with ignition and goes off when the car starts as it should. I replaced every fuse because I didn’t see why not. Alternator case must grounded to get readings.

I’m just at a loss getting no alternator performance at all over two identical alternators when all other surrounding systems seem to functioning. Any insight would be much, much appreciated. Thanks!

[SteinOnkel]

Hmmm, that seems very strange.

Is your multimeter working?

I would also think it's impossible to drive a gasoline powered car for an hour if the alternator isn't charging.

[Stookie]

I’m thinking multimeter should be good if I’m getting what seems to be the right reading on the battery itself. And I’d agree, does seem weird it would run that long, but it was a brand new battery right before the journey. Not sure. Died on a test drive just an hour after getting home.

New information. Tested voltage at exciter wire on the alternator and get nothing, car on or off. Oddly though, the charge light on the dash comes on with ignition on even when the exciter wire is not connected...?

[18Fiatsandcounting]

I think the AR 95 amp alternator has an internal voltage regulator, but a 1976 spider was originally wired for an external regulator (mounted on the driver's side firewall). If your setup isn't wired correctly for the 95 amp version, the alternator won't work.

Fiat switched from external regulator to an internal regulator setup in late 1977, so essentially model year 1978 and later.

I can walk you through the overall changes if needed.

-Bryan

[18Fiatsandcounting]

PS: It's possible the original AR alternator is fine, but if it was bench testing without a load on it (the battery), the power transistor in the internal voltage regulator could be fried. Old school alternators could operate without a battery attached, but the modern ones don't take too kindly to that.

[Stookie]

The po before the person I bought it from did the wiring change but there’s no way I can confirm it was ever right. Seems strange though that they would know enough to find that alternator and uprate some other items but never have had that wiring right. But it’s a good lead to follow.

I have three black wires going to the output on the alternator, as well as the yellow wire on that alternator. So 4 wires on the output. The part I’m not even sure where exactly to look for is the change that needs to be made for the charge light relay. The guys at autoricambi seem to think that for the charge light to even come on in the dash that this change would need to have been made. Does this sound right?

What would I look for to verify that change was made correctly. I know it should be on the driver side fender, but besides that not sure what I’m looking for

[18Fiatsandcounting]

A few thoughts:
1. If by chance an LED lightbulb was installed in the alternator warning light instead of the original incandescent bulb, the alternator won't work. LED bulbs in this location don't allow enough current to flow through them to energize the field coil of the alternator, so it doesn't work.

2. Here's a quick test. Disconnect the wire labeled as D+ (dynamo positive) on the alternator. Turn on the ignition, but don't start the car. Measure the voltage on that wire that went to D+. It should have 12volts on it (or whatever your battery is at). If you don't see 12 volts, either the wiring for this is wrong, or you have an LED bulb.

3. Check the fuse box, as I believe Fuse L (the one furthest from the steering column) supplies power to the alternator field coil. Make sure it's not burned out.

3. Since you have a new battery, it's likely the alternator was never working and the car ran only long enough go get home. With no headlights/cooling fan/heater fan/wipers, a new battery might last a few hours. With those items running, much less.

4. The external voltage regulator is a black box with rounded edges on the driver's side firewall near the top. It has two terminals at the bottom, with usually large orange and grey wires. It looks like this: https://autoricambi.us/voltage-regulato ... -external/ If this is still there and connected, the wiring hasn't been modified correctly. In the original, the orange wire goes to terminal 15, the grey wire goes to terminal 67, and the case itself is grounded to the car body.

-Bryan

[Stookie]

Thanks for the detailed responses! Is the d positive on the autoricambi alternator the green wire that goes to the exciter? The only other two wires are yellow, that goes on the alternator post, and a gray wire that is already plugged into a clip on the alternator itself. Just want to be sure I’m checking the right thing.

I’ve checked that green wire that leads out to the yellow slash red wire that should be the exciter. I get 0 volts there. Should I check a different wire?

[spider2081]

I think a 1976 Spider used a relay to turn on the battery warning light. When an alternator with built in regulator is installed the voltage regulator and the relay are not needed. That requires some rewiring.
Have you asked Autoracambi for the alternator installation instructions and wire modification instructions/diagram??

[18Fiatsandcounting]

Stookie, thanks for the info. I think someone wrote up a summary of this (spider2081, was that you?). Here's basically how I see it.

The Fiat alternator needs an exciter voltage (current) which is what creates the electromagnetic field around the spinning rotor of the alternator. Older alternators (pre-1978) got this exciter voltage from the grey wire which came from the voltage regulator, and the regulator cycled this voltage on/off depending on whether the charging voltage was below or above the set point of around 14.6 volts. The old style alternator also had a yellow wire that went to a relay, and the yellow wire "sensed" when the alternator was producing output, turning off the alternator light with the relay. It couldn't do this by sensing the alternator output itself, because that was connected directly to the battery and so it would always read 12 volts or above, making it a meaningless measurement.

Newer alternators have the regulator built in, and so the only connections to them are the alternator output to the battery and the car's electrical system, and the wire for the exciter. The exciter wire (perhaps green?) went through the alternator warning light bulb to the positive of the electrical system (when the ignition is on). So, if the bulb is LED or burned out, no voltage to the exciter wire and thus no current to energize the electromagnet of the rotor of the alternator.

OK, I realize that all of Bryan's theory is not helping you solve your issue. I can continue to offer diagnostics, but the quicker course of action might be to call AutoRicambi and see if they have a ready-made solution for this. I'd all be willing to chat with you over the phone, and you can PM me if you want that option. I'd be happy to detail more info here, but it would be a lot of typing!

-Bryan

[18Fiatsandcounting]

Is the d positive on the autoricambi alternator the green wire that goes to the exciter?

I believe so, yes, but I'm going by memory here... Do you have an electrical diagram for your 1977?

-Bryan

[Stookie]

Well, I made a discovery. After getting off the phone with autoricambi I was able to figure out where the battery charge relay was and that it had not been spliced by the po the way it was supposed to. It was left as stock, so no charge was getting to the positive terminal of the alternator.

So, I hookup alternator to its own stud, and we get charge. So, the issue is getting power from the ignition through the purple wire that was supposed to be spliced. Somewhere between the key cylinder and the battery relay, there is a bad connection on that purple wire.

This brings to light why the po had made a diagram of the connections on the back of the key cylinder. I’m guessing they were fooling with it so much trying to figure this same issue out that they wanted a primer on how those wires go.

So, I found a hot 12v source going into the old voltage regulator and just spliced from that directly to the positive of the alternator, and boom. Charging system works perfectly.

So... that is not a permanent fix, but it is working. If I decide to go further, going to have trace that purple wire into the dash and behind the radio, but at least we have our answer! Thanks to everyone for the input, very much appreciated from a new member!

[18Fiatsandcounting]

Awesome, Stookie, and yes, if you don't have a solid +12V going to the alternator, it won't work.

Glad you figured it out. One question: Does your alternator light work? It should come on when the ignition is turned on and go off when the engine starts, if everything is working as it should.

-Bryan

[Stookie]

I will have to check that tomorrow, at the moment just getting the car started and seeing 14.4v at the battery terminal was enough to end a long two days for me. Haha.

I believe that even though it is an end-around jury rigged fix, 12v is 12v no matter where it comes from...and since I don’t need the old voltage regulator, why not just steal the power from there?

My car is by no stretch a show car and never will be so as long as this works ok for occasional cruises and getting ice cream with my wife I probably won’t dig too much deeper into this particular issue. Besides this, the car runs great and oil pressure and engine temps are solid.

Tearing the dash apart to take my 12v from the proper purple wire instead sounds like a winter project I might get to at some point though. Tinkering never stops!

[DieselSpider]

Awesome, Stookie, and yes, if you don't have a solid +12V going to the alternator, it won't work.

Glad you figured it out. One question: Does your alternator light work? It should come on when the ignition is turned on and go off when the engine starts, if everything is working as it should.

-Bryan

And that Solid +12V is critical to the operation of the internal voltage regulator since that is what provides the feedback it needs to operate properly. If there is more than a 0.02 to 0.03 volt drop between the reading at that wire from whats at the battery you can end up with an overcharging situation and found that with the voltage drop on the original exciter wire that charging was at times upwards of 15 volts at the battery.

Myself on the Diesel I just converted the Hitachi Alternator from Internal to External voltage regulation which allows me to use an easily replaced adjustable regulator mounted on the fender far from any heat sources.

The internal regulator on that one has 5 pins on it that have to be soldered to a mounting plate plus you have to completely disassemble the alternator to get to it which includes removal of two oil lines, one vacuum line and the vacuum pump mounted on it to run the brake booster since diesels have not throttle plate so develop no real intake vacuum.