Alternator in need of rebuild in 1986 S3 Spider? - Alfa Romeo Bulletin Board & Forums
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post #1 of 13 (permalink) Old 07-07-2018, 07:49 PM Thread Starter
Lew
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Alternator in need of rebuild in 1986 S3 Spider?

My voltage gauge reads below 12V at idle and the red battery warning light glows red. My multimeter says the voltage at the battery is 12.52V prior to starting, 12.18V at idle, and 12.17 at 2,000 RPM. The voltage at idle and 2,000 RPM are steady (when tested for 15-20 seconds). The voltage at the fender junction box is 12.47 prior to starting, 12.15 at idle, and 12.12 at 2,000 RPM.

All of these voltages are with no electrical load. The battery was charged with a charger rather than being charged from the alternator.

I understand I should be seeing 13+ volts when idling/running, so it seems the alternator is not charging correctly.

I have the Bosch 0 120 489 903 904 (K1 14V55A20) alternator with the Bosch 1197 311 005 voltage regulator on it. Might replacing the regulator fix the problem? or are the other parts in the alternator likely the problem and it needs rebuilding?

The local alternator repair shop has quoted me $89 to rebuild it. I’ve seen a “refurbished” Bosch 1197 311 005 regulator for $19.95 shipped.
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post #2 of 13 (permalink) Old 07-08-2018, 12:55 AM
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No such thing as a 'refubished' regulator. That would be like a refurbished cigarette. But they are still cheap enough to buy...that is probably your issue; I've been in the same boat with other Bosch type alternators. If you can find an adjustable regulator, get one of those. If your tired alternator is pumping out 13.7 or so, which is very marginal, you can adjust the regulator via a pot with a small screwdriver to reach 14V or more. Anything below that sucks, even though it's still in spec.

I think a new reg will do the trick, but if not, the quoted price for a rebuild is really good. And when I had mine rebuilt a few years ago, he installed a new adjustable regulator....
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post #3 of 13 (permalink) Old 07-08-2018, 03:19 AM
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when you remove the old regulator, check if the brushes are worn down unevenly, if so it might point to a worn commutator, in which case the alt needs to be seen to in any case as a bad comm. will eat through the new regulator brushes again.

your alt belt is not so loose that it is slipping, right?...one presumes you have removed and cleaned all connections on the alt (including the ground screw of the regulator, one of the 2 screws that holds it in)

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #4 of 13 (permalink) Old 07-08-2018, 06:53 AM
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when you remove the old regulator, check if the brushes are worn down unevenly....
spiderserie4 offers good advice. No matter what you do, you have to begin by removing the alternator. Once you have done that, pull out the regulator-brush assembly and examine it.

- If the brushes are worn, that is likely your problem, and installing a new regulator-brush assembly should solve it. However, as spiderserie4 points out, if the commutator is rough, it will wear the new brushes quickly.

- If the brushes look OK, then it could be the regulator electronics but they would be tough to diagnose. At that point, you could gamble $20 that a new regulator-brush assembly will fix it, or go for the professional rebuild.

As John533i points out, $89 to rebuild an alternator sounds like a heck of a deal, assuming they do a thorough rebuild. For that low a price, they may just be swapping in a new regulator-brush assembly and testing it.
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Last edited by Alfajay; 07-08-2018 at 07:00 AM.
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post #5 of 13 (permalink) Old 07-08-2018, 07:41 AM
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What if you have the opposite problem? I measured almost 16v yesterday on mine.


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post #6 of 13 (permalink) Old 07-08-2018, 09:16 AM
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No need to remove the alterator to replace the regulator. You only need to remove the air filter box to gain adequate access to the back of the alternator. Remove the black plastic air cooing cover from the rear of the alternator (if yours has one), then unbolt the regulator and replace it. Disconnect the battery first of course. I think I paid $34 for a new Bosch regulator last year.
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post #7 of 13 (permalink) Old 07-08-2018, 09:27 AM
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What if you have the opposite problem? I measured almost 16v yesterday on mine.
That pretty much has to be the electronics part of the regulator-brush assembly. I assume that by 1991 Alfa was using integrated alternator-regulator (like the one shown in Norseman50's post), and not the earlier, separate alternator and regulator. But either way, your regulator is on its way out. Fix it promptly; voltages much higher than 16V will fry your electronic components.
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Jay Mackro
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'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L

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post #8 of 13 (permalink) Old 07-08-2018, 09:30 AM
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What if you have the opposite problem? I measured almost 16v yesterday on mine.
well, first I wouldn't drive it or you might fry something.

but that does sound like the Voltage Regulator, not "regulating"

edit: wot Jay said!

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #9 of 13 (permalink) Old 07-08-2018, 02:14 PM
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Originally Posted by Alfajay View Post
That pretty much has to be the electronics part of the regulator-brush assembly. I assume that by 1991 Alfa was using integrated alternator-regulator (like the one shown in Norseman50's post), and not the earlier, separate alternator and regulator. But either way, your regulator is on its way out. Fix it promptly; voltages much higher than 16V will fry your electronic components.
Yah, but the lights are nice and bright!!! (while they last)

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post #10 of 13 (permalink) Old 07-08-2018, 02:31 PM Thread Starter
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Your alt belt is not so loose that it is slipping, right?...one presumes you have removed and cleaned all connections on the alt (including the ground screw of the regulator, one of the 2 screws that holds it in)
The alternator belt is new and tight, so not an issue there. The red positive terminal and small green wire connectors are clean, but I was unaware that one of the screws on the regulator is a ground, so I'll check that too. If that's not the issue, I think I'll try a new regulator when I get back to the project next week before deciding to have it rebuilt.

Should I be concerned with the slight part number difference between the Bosch 1 197 311 005 regulator that is on my 1986 and the 1197 311 028 part number in Norseman50's photo (or the 1 197 311 090 in Centerline's photo). What is the significance of the last 3 digits in the part number?

Lew
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post #11 of 13 (permalink) Old 07-08-2018, 02:46 PM
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False alarm for me. The battery on my multimeter was low and it was reading inaccurately. I was smart enough to check my E30 which also read 16v before ripping apart the Alfa


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post #12 of 13 (permalink) Old 07-09-2018, 12:24 AM
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Edward, that's interesting about that cover for the back of the alternator. I'm wondering if mine is overheating from engine temps, as the voltage will drop once the engine starts to heat up. 14.2V at idle when I first start it; 13.8V after I've been driving.

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post #13 of 13 (permalink) Old 08-14-2019, 04:54 AM
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Hello Lew,

Did you ever get a response regarding the part number difference between the Bosch voltage regulators?

Thanks,

Bruno

1973 Alfa Romeo Spider Junior (Euro) 1300
1993 Alfa Romeo Spider Veloce
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