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Discussion Starter #1
My '71 GTV has a 2L Alfa Ricambi, Spica injected engine, and a stock looking Bosch alternator # 0 120 400 528 also marked with K1 14v 35a 2c on the serial tag. This alternator was just rebuilt by a local alternator/starter specialty shop - it is the version with 4 different nut/washer attached terminals and all crimps and eyelets look fine. The battery has been moved to the trunk and all connections look clean and tight.

I have owned the car for 6 months and all of this has been working flawlessly. The jell cell battery has never seemed weak, but the "generator" light started coming on a few weeks ago, prompting me to inspect the inside of the voltage regulator first. All looks clean and orderly in there to me, and a little shot of DeOxIt didn't seem to change things. Next I had the alternator rebuilt with new bearings and brushes.

The light still comes on, but not in the same way. Before the alternator work, it would come on at about 2500 rpm and then go off above 4000. Now it just stays on, but not very brightly. Two separate volt meters have shown the running car to be producing up to 17.8 volts at the battery. The alternotor shop says their bench test shows an internal short for all 3 voltage regulators I scrounged up. I had tried all of these on the car - so if they are right, I am cooking more than the battery. These same people in the shop say I should be looking for a loose ground or even a loose positive lead anywhere on the car.

All looks good to the eye - where should I start and how should I test for perfect connectivity?

Thanks,
Tim.
 

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Hi Tim,

Welcome aboard the Board!

There's only three causes I can think of that would cause an alternator to "full field" (ie put out max amps and unregulated voltage).

1) bad regulator
2) internal short in the alternator to field
3) alt/reg wiring

Try this test; check the charging voltage with the regulator disconnected. If the voltage does NOT go up, the alt would appear to be OK.
Referring to the pics, check the wiring.

Term #1 - D+ Green wire
Term #2 - B+ Red to battery
Term #3 - DF Black
Term #4 - D- Brown

Dimly lit alt or gen lights with a properly functioning charging system are almost always caused by loose/dirty connections, particularly fuse #6.
 

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Discussion Starter #4
Great post - great pictures.

Mine is exactly like the one in the pictures, except I have two green leads to the same connector at the voltage regulator. All is connected correctly and cleanly.

When I disconnect the voltage regulator, I get steady voltage between 12 and 13 volts when measured at the alternator, and also when measure at the battery in the trunk. Per your reply, it would seem that this means the alternator is OK. Where should I check next? Can I drive it without the regulator?

Thanks again.
 

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To answer your last question first, yes, you can drive the car without the regulator BUT only 'til the battery goes dead. Depending on the battery's state of charge/condition and the load it's under, that could be anywhere from 5 mins. to 5 hours.
The reason to check the voltage with the reg disconnected is to determine if the alt has an internal short from battery to the field terminal. Since the alt is not full fielding with the reg disconnected, it would appear that the alt is OK.
The second green wire on your reg plug goes to alt light on the dash. The pic was taken from a 68 Euro version which has the second green wire attached to the alt instead of the plug.
Well, it would seem that regulator is the problem. But 3 shorted regulators? Possible. Were any of them known to be good before installation? Were they properly grounded?
My thought would be to take the alt back to the rebuilder and have them benchtest it with regulation. If it tests OK, I'd install a new regulator.
 

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Discussion Starter #6
Almost solved

My battery is apparently very strong. I drove it for about an hour and a half with no regulator and for about 10 days with the overcharging condition until I "adjusted" my bad regulator to get it to limit the voltage. It still cranks over as stronlgly as ever. Here is my solution so far:

After cleaning all connections to the alternator, the regulator and the battery, and even adding a new ground from the engine to the body, I adjusted the spring tension inside the regulator. I did this by simply bending the metal tab that the spring steel piece is anchored to inside the Bosch voltage regulator. By so doing, I have reduced the amount of force required by the magnetic winding to move the contact point to limit the voltage.

According to my voltmeter, I now get a very consistent 12.5 - 13.8 volt range no matter what load or RPM. This is true when measured at the alternator or at the battery, which was moved to the trunk. HOWEVER, my generator light on the speedometer still is not happy. It correctly glows brightly when the ignition is on but the engine is not running, and it glows faintly (but annoyingly visible at night) at all other times. Is there a ground here that I need to track down and clean somewhere under the dash?

Thanks for all your help. I feel I am close to resolution on this one.
 

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Sounds like your almost there.
The generator light works like this; when the key is turned on, voltage goes to one side of the bulb. The other side of the bulb, the green wire, goes to the alternator. Because the alt is not charging, the green wire is grounded thru the alt completing the circuit and the light lights. When the alt is charging, the green wire switches from being a ground to supplying the bulb with system voltage. Since the bulb now has positive voltage on both sides, and no ground, the light goes out.
A glowing bulb means that these two positive voltages are not equal. Since the charging system has been proven OK, and the green wire goes directly to the bulb (well, almost) I'd suspect a voltage drop on the switched side of the bulb. A good place to start would be to clean all the connections at the fusebox as well as all the fuses; particularly fuse #6.
 

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i know this is an old thread but this is the beauty of this forum.. papajam once again comes through with his infallible knowledge of alfas.. i just aquired a really nice 71 giulia super from fellow bber hardtop in MA. i noticed yesterday as i started driving it the alt light came on and stayed on.. checked the voltage at the battery and revved up the motor and was getting over 14v to the battery.. soo the system is working. did a quick search this morning on the bb and the last post caught my eye. went outside at lunch and pulled fuse #6 and sort of twisted it in my fingers in the fuse holder to "seat it" (for a lack of a better term) and remove any oxidation and make better contact and voila'... fixed the problem.

thanks jim. this bb rules. :)
 
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