Alternator failure? Or not? - Alfa Romeo Bulletin Board & Forums
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post #1 of 14 (permalink) Old 11-04-2018, 12:07 PM Thread Starter
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Alternator failure? Or not?

Hey Alfisti,

I'm looking for some guidance regarding a potential alternator issue.

I have a '72 GTJ1300 (2l fitted). I was out for a drive on Friday night, the car was running sweetly. Then the alternator warning light would become fully lit for sustained periods - perhaps 2 or 3 mins, then revert to normal behaviour.

Eventually it become fully lit permanently. Once home I performed some diagnostics with the voltmeter. Results are:

Battery reading, engine off - 12.45v
Battery reading, idle - 12.89v
Battery ready with some rpms added - between 13.5v and 14.6v, revs dependant.

I'm taking this as the battery being good, and also the alternator providing a charge.

Is the warning light lying to me? I cleaned up fuses/terminals 6 and 7 and inspected the alternator - belt looks good etc.

What else can I check? I have a sneaky feeling this is an electrical gremlin rather than impending alternator failure but what do you think?

Also, the car is just back from the shop after having electronic ignition fitted? Would it be wrong to assume some wiring may have been disturbed? Earth strap perhaps?

Thanks in advance

Tom
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post #2 of 14 (permalink) Old 11-04-2018, 02:42 PM
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A fully charged battery (with everything off) should read 12.6V. 12.3 is half-charged.

When the warning light illuminated had you switched on any additional loads (wipers, blower motor, etc)?

When dealing with any electrical issues, the first thing I do is make sure all connections are 100%. Don't assume they are OK because they look good or feel tight - one by one remove, clean and secure. Especially with connections to aluminum - aluminum oxides can be aluminum colored so not plainly obvious like rust on steel. I like to clean the connection area and apply some dielectric grease. This helps prevent corrosion but will not impede a properly snug electrical connection.

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post #3 of 14 (permalink) Old 11-04-2018, 04:24 PM
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Quote:
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When dealing with any electrical issues, the first thing I do is make sure all connections are 100%. Don't assume they are OK because they look good or feel tight - one by one remove, clean and secure. Especially with connections to aluminum - aluminum oxides can be aluminum colored so not plainly obvious like rust on steel.
ghnl offers good advice, particularly when dealing with 1970's era Alfa alternator systems. These alternators use an external voltage regulator, which is typically mounted in front of the battery / to the left of the radiator. The weakest component in the system is the harness connecting the alternator-regulator. It's possible that your problem is as simple as a corroded or partially-broken connector on that harness. The alternator end tends to degrade as it is subject to the heat from the exhaust manifold.

If you check that harness and are convinced that it's OK, then the alternator is the next most likely component to be bad (or in your case, intermittent). The regulators can also fail, but in my experience, are the most reliable of the three components.

Quote:
Is the warning light lying to me?
It sounds as if your light is working correctly. There isn't much that can go wrong with a warning light; when they fail, the symptom is usually that they are dark all the time (e.g., blown bulb, broken connection). They don't fail by flashing on and off randomly.

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Last edited by Alfajay; 11-04-2018 at 04:27 PM.
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post #4 of 14 (permalink) Old 11-05-2018, 04:31 AM Thread Starter
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When the warning light illuminated had you switched on any additional loads (wipers, blower motor, etc)?
The only additional load was from the interior light. Everything else was off.

This is great advice guys - I'm new to the world of classics and also new to the world of fixing cars myself so I'm learning on the go

So, next job is to fully clean all connections and go from there.....what is your recommended routine for this?

I'm proposing

- Clean connectors with fine sandpaper/small wire brush
- Blast with compressed air
- Clean again with contact cleaner
- Apply all contact surfaces with dielectric grease and re-attach

What do you think?
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post #5 of 14 (permalink) Old 11-05-2018, 07:06 AM
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I like the small wire brush. Even fine sandpaper can remove too much material - best is to remove only the corrosion.
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post #6 of 14 (permalink) Old 11-05-2018, 10:16 AM
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If you have a Bosch installation, the regulator and alternator are connected through 3 wires.
(I suppose for other systems the setup is quite the same)
I would certainly check the wiring (actually, three wires) going from the alternator to the regulator.

Are the connectors on both sides in good shape? Mine once was disconnected at the alternator side...
No bended or damaged cables?
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post #7 of 14 (permalink) Old 11-05-2018, 11:20 AM
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Quote:
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I'm proposing
- Clean connectors with fine sandpaper/small wire brush
- Blast with compressed air
- Clean again with contact cleaner
- Apply all contact surfaces with dielectric grease and re-attach
What do you think?
Well, that's the "right" way to do it. But honestly, you can begin by just looking for major problems - things like frayed and broken wires. It isn't unusual to find just a few strands still connected to the terminals on these 45 year old harnesses.
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Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L
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post #8 of 14 (permalink) Old 11-10-2018, 12:30 PM Thread Starter
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Update!

Spent some time checking and cleaning the wiring and connectors - no obvious fraying or looseness.

No change to the warning light - it remains lit.

I did do another voltage check, paying a bit more attention to the readings:

Engine off - 12.7v
Engine at idle (no other electrical load) - 12.9v

I'm expecting a clear 0.5v charge at this point right?

If so, it seems clear I'm only getting a partial charge and suggests the alternator is indeed on it's last legs.

What would you recommend to replace? Alfaholics supply a refurb unit for a reasonable cost which I would try to fit myself - provided it's a like for like swap.

Or should I be looking at an upgrade with internal voltage regulator? I guess this would mean one less junction to cause problems but the downside is some wiring changes, which I'm not confident to tackle myself.

On the upside, a good clean of the ground connections has resolved two electrical issues with my rear light/turn signals! Every cloud and all that.....
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post #9 of 14 (permalink) Old 11-13-2018, 03:07 AM
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Should be charging properly at idle, 14 volts or so. I tested a new alternator the other day by running it up using an electric rattle gun and it gave 14.5 straight off.


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post #10 of 14 (permalink) Old 11-13-2018, 03:52 AM Thread Starter
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Should be charging properly at idle, 14 volts or so. I tested a new alternator the other day by running it up using an electric rattle gun and it gave 14.5 straight off.
Ok, new alternator time then. Keeping to my ethos of always improving the car, I will get the integrated alternator/volt regulator.

Thanks for everyone's input
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post #11 of 14 (permalink) Old 11-13-2018, 06:42 AM
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Ok, new alternator time then. Keeping to my ethos of always improving the car, I will get the integrated alternator/volt regulator.
Again, the fault may be in your regulator, rather than alternator. But one or the other does seem bad, so if you replace them with a more modern alternator with integrated regulator, you should eliminate the problem.

In terms of where to get a replacement: later Alfa spiders, as well as Milanos, used an internally-regulated Bosch alternator that will bolt on to an earlier Alfa engine. These are available from the usual parts suppliers. Even a used unit is a good bet, as the brush/regulator assemblies are inexpensive and simple to replace. The modification to your car's wiring will be pretty simple and is well-documented here on the BB.
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Jay Mackro
San Juan Capistrano, CA

'63 Guilia spider
'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 11-13-2018 at 06:56 AM.
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post #12 of 14 (permalink) Old 11-13-2018, 07:56 AM
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Having recently suffered alternator gremlins at Monterrey this year let me caution that problems can be intermittent and confounding. In my case it was no charge and no red light.

I first suspected the bulb was burn, so no current to excite the alternator. Pulled the alternator (no small feat on my v6 converted 67 which has a late model Milano alternator beneath a a/c compressor on a bespoke mount all of which had to be removed) and had it checked in Watsonville where it was pronounced "OK" On re install it was making electricity again till the last day of the Monterrey week.

Made it to 50 miles of home then got flat bedded the rest of the way.

On tear down the brushes/slip rings were worn making intermittent contact and finally gave up taking the regulator down as well. would work for a while, then not and finally forever not.


all better now.


Many off the shelf rebuilt alternators (and generators and starters) are junk. I would try and find a crusty shop with an old guy who has been doing them for years, have yours diagnosed and completely rebuilt.

Just my 2 cents.
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post #13 of 14 (permalink) Old 11-13-2018, 11:09 AM
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I too think another alternative to a new alternator is just to find your local starter/generator/alternator rebuild shop and get them to do it. Well worth seeing if you have a local one at least.
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post #14 of 14 (permalink) Old 11-13-2018, 07:40 PM
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It's fairly easy to replace the brushes in an alternator, and polish the commutator of the alternator axle.

You can get a perfect fit of the brushes to the rotor by taping a piece of 200 grit W/D paper to the commutator and hand rotating the assembly to form the brushes to the commutator.

BTW - one of the best ways to clean terminals is a pencil eraser. It's just the right grit to get the oxides off but not damage the metal. Been used in the electronics industry. Also - NOT one of those big Pink Pearl erasers.

I agree the later alternators with integrated regulators are much more reliable. Most are also higher amperage capacity. I got mine from APE.

Robert
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