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Discussion Starter #1
Hello everyone.

I'm having an issue with my alternator... actually with three of them, which makes me think the issue lies somewhere else.

The problem is that I am not able to get more than 13V out of any of the three alternators I have installed on the car - the original 65W GTV6 one, and two 70W Milano ones purchased from APE. They all give me the same 13V at every RPM. Above 2000 RPM the alternator light turn bright red and when driving at night with the lights on, the battery is drained as the 13V drops to less than 12V.

Does anyone have a clue on what the problem may be?
Thank you all in advance.
Igor
 

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Bosch alternators?

You'll probably find it has a poor earth to the chassis or a voltage drop across the wiring loom under load.
 

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Voltage is pretty much independent of rpm = it is controlled by the voltage regulator. Alternators must be run at certain rpm to produce current and typically they will make 50% of the rated output at around 2000 rpm. The voltage will be dragged down if you load the alternator with a high current demand at low rpm.

I agree with the suggestion that you check the ground connections including the one that completes the ground circuit between the engine and the chassis. Also check the obvious - loose drive belt.
 

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I went through a similar thing on my Spider. Please see my post and write up here.

Bottom line, I bought a smaller pulley from Quality Power and that made the RPMs higher so that more current was produced at idle as Ed mentioned.

What I was wondering is if this low alternator speed and battery drain at idle is by design in Alfas. Does everyone have this problem when they're in traffic and the fans and lights are on?
 

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I have a small engine pulley to reduce the speed of my alternator. i regularly rev my motor to around 7000 rpm and high revs kill alternators. I have no charging problems but I hardly ever use the lights and I have no radio - just an ignition system that requires a few amps, an electric fuel pump and an electric cooling fan.
 

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I cant remember if it was Dickman Jr. that had this issue or somebody else that was chasing the same kind of problem. They solved the problem by checking all the ground connections and if I remember correct solved the high rev issue also by going to japanese alternator (I think Mitsubishi).
 

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Discussion Starter #8 (Edited)
Thank you all for your input.

I don't think it is the pulley... why would the pulley size be fine when it came out of the factory and not today using the same alternator? I think it most likely has to do with the ground connections.

My question, though, is... (I know this may sound silly) where is the ground connection for the alternator. There are two wires coming from the alternator: a thick red one and a small green one. These go to a little black plastic box on the inner fender. Is this what I should check/clean. I did open up the little black box this morning before taking off for work and found the thick red wire burnt:

IMG_20141104_094226.jpg
IMG_20141104_094245.jpg

I think this may be the culprit. I will clean it up and maybe replace the wire this weekend and see what happens.

Thank you all again for your help.
Igor

PS Please note that the alternator light does turn on when in idle - it seems to be producing enough power when idle. It turns on above about 2000 RPM - indicating that is not producing enough in that condition... at least, that what I think...
 

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The alternator is grounded through the metal casing, through the engine block and then through a cable that connects the block to the body. That cable may be connected close to the alternator bracket.
 

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Discussion Starter #11
That one I checked a while ago and am 100% sure is fine.

The alternator is grounded through the metal casing, through the engine block and then through a cable that connects the block to the body. That cable may be connected close to the alternator bracket.
 

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I suspect it's that connection you found. If there's resistance there you're not going to get enough current into the system no matter how much the alternator tries to pump out.

You shouldn't need to mess with the pulley. I mean, it might make things better for some folks in some cases, but it won't help with the symptoms you're having.
 

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I agree the first thing is making sure the grounds and all contacts are good. The connections in the photo look pretty bad, I would definitely clean those up.

In my case the low RPM alternator was non stock and I confirmed the RPMs were too low at idle. With my new pulley ratio and the Delco's 18,000 RPM continuous rating, my crank RPM limit is 8000 RPM....above redline, plus I'm seldom above 5000 (I know I'm boring).

But, I recall when my stock alternator was working that it wasn't charging at idle with fans and lights running either. Maybe my stock alternator was marginal to begin with.
 

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I had the same issue with my GTV6 and like ghnl says a voltage drop test is pretty simple to do. I found the drop at the alternator bracket or b lead I believe. Cleaned and sanded, no more issues. I your case that wire sure seems suspect :)
 

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Alternator rpm vs output

I was checking out an electrical circuit on my GTV and I decided to check the alternator output. I turned on the main beams and the currect to them was 22 amps. There was additional current to the rear lights, etc that I did not measure. With the engine idling at 600 rpm the alternator output voltage was 13.3 volts. When I stopped the motor the battery voltage dropped to 11.6 volts. This supports my earlier post that alternators do not have to be spun fast to provide good output.
 

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Lights were not a problem for my Spider's alternator either, but lights + fans were. lights+fan+heater ...foggetaboutit. In evening stop and go traffic, my battery would eventually discharge and I'd have to pull over.

I would expect and hope that Alfa originally designed the system such that output at idle would be enough to charge the battery with lights+fan+heater going. On my car it never worked with the alternator present when I bought it. But as I said, maybe my alternator was bad. Now after a few months, I can run everything I want at idle with no fear of battery discharge.

In any case, the RPM to measure is at the alternator not the crank (unless you know the pulley sizes and convert the RPMs). I think all alternators have a similar output curve to this one - the key is whether the amps produced at the low RPM are enough for your load.
 

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Dear Igor,

Clean all connections and change which ever wire or wire connections which are no good.

Then check your voltage at idle and voltage at idle with your lights on.

I had 13.7 V at idle and once lights are on than there would be voltage dropping to 12 V.

I added one more red cable from alternator to a wire junction on inner fender under that plastic where is the original red wire also coming from alternator and I got 14.3 V.

But still I had a remaining problem of voltage dropping to a 12.5 V once lights are on at idle speed.

After that I added relays to a headlights and now I have 14.3 V at idle and when I turn on the lights at idle I have 14.2 V.

Problem solved but not quite bacause when you have windscreen wipers on plus cabin ventilator plus lights plus direction indicator then everything slows down.

My opinion is that the main problem is FUSE BOX.Why?
Because what ever I turn on now the red alternator light is still slightly burning red as before but no more burning red when only lights are on since I installed relays.

To permanently solve the problem we should install new fuse box or boxes like boats have or try to install a fuse box for example from a 75/Milano which is much better than a one we all have in our cars.

By the way all GTV 6 world wide have the same issues.

Cheers :smile2:
 
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