Hello all,
I am working on a Fulvia Sport for a friend who has had the car for a couple of years but not used it at all.
I fitted a new battery (started first time...) but noticed that the alternator appeared not to be charging so i removed it for inspection. Upon removal i noticed that the alternator appeared to be a replacement and in great condition with no apparent signs of corrosion. The problem appears to be that the thing wasn't connected at all - I can only assume that this had been done to turn off the warning light on the dashboard before it was sold!
I found the L-shaped connector for the back of the alternator easily but there is another single 'standard' male spade connector on the back of the alternator with a plus (+) sign next to it and there doesn't appear to be a spare wire with a female spade connector on it lying around - which makes me wonder if it needs one?
If any of you could shed some light (sorry...) on this i'd be sincerely grateful.
Andy
Alternator wiring
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Peter Cripps
Re: Alternator wiring
Andy,
If the 2 connections you mention are the only ones on the alternator, then it sounds as if it is indeed a replacement, with a built-in regulator. The original alternator would have had an external regulator, connected to the alternator via 3 additional wires.
The big L-shaped connector goes to 12V. If the original fat red alternator wire is present, then that would be the one to use. And, assuming that the + connection is for the alternator field (maybe actually labeled D+?), then it should go to the warning light (red/black on my Fulvia).
I am also assuming that the warning light is wired up as on my Fulvia, that is, one side goes to +12V via the ignition switch. You can check this by grounding the red/black wire and seeing if the warning light goes on when the ignition switch is operated.
The way this works is as follows:
At zero or very low rpm, the alternator is not producing any output. Current flows from the battery, through the warning light, and excites the alternator field winding. Then, the alternator starts to produce output, which starts to take over field excitation from the light current. At anything above a few hundred rpm, the alternator produces full output, and provides its own field excitation. The light then goes out, since both its terminals are at full battery voltage.
Hope this all makes sense,
Peter
If the 2 connections you mention are the only ones on the alternator, then it sounds as if it is indeed a replacement, with a built-in regulator. The original alternator would have had an external regulator, connected to the alternator via 3 additional wires.
The big L-shaped connector goes to 12V. If the original fat red alternator wire is present, then that would be the one to use. And, assuming that the + connection is for the alternator field (maybe actually labeled D+?), then it should go to the warning light (red/black on my Fulvia).
I am also assuming that the warning light is wired up as on my Fulvia, that is, one side goes to +12V via the ignition switch. You can check this by grounding the red/black wire and seeing if the warning light goes on when the ignition switch is operated.
The way this works is as follows:
At zero or very low rpm, the alternator is not producing any output. Current flows from the battery, through the warning light, and excites the alternator field winding. Then, the alternator starts to produce output, which starts to take over field excitation from the light current. At anything above a few hundred rpm, the alternator produces full output, and provides its own field excitation. The light then goes out, since both its terminals are at full battery voltage.
Hope this all makes sense,
Peter
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Andy Craig
Re: Alternator wiring
Peter,
That's a great help, many thanks. The connector does indeed go to 12 volt so i'll assume for now that it's ok. I can see no other stray wires which could go to the D+ connector on the alternator. Would i be correct in saying that, if operating correctly, the system would not charge in the absence of the D+ connection and could this explain it's absence on the first place - that someone didn't bother to hook one up?
Andy
That's a great help, many thanks. The connector does indeed go to 12 volt so i'll assume for now that it's ok. I can see no other stray wires which could go to the D+ connector on the alternator. Would i be correct in saying that, if operating correctly, the system would not charge in the absence of the D+ connection and could this explain it's absence on the first place - that someone didn't bother to hook one up?
Andy
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Peter Cripps
Re: Alternator wiring
Andy,
Right, you need the initial excitation current through the warning lamp. In fact on some cars there is a resistor wired in parallel with the lamp, so that if it fails you will still get some current.
Peter
Right, you need the initial excitation current through the warning lamp. In fact on some cars there is a resistor wired in parallel with the lamp, so that if it fails you will still get some current.
Peter
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Huib
Re: Alternator wiring
And check the grounding wires. The alternatore is mounted in rubber / plastic. Its casing is thus not electrically connected to the engine. This should be done first. Originally this was done with a short wire with an M6 lug and an M8 lug between the adjust bolt of the alternator and one of the M6 bolts of the cover of the auxiliary shaft where the fuel pump is.
Then one from the engine to the body. I usually put it from one of the 4 M8 bolts fastening the engine side support to an M8 bolt in the inner wheel arch.
When an alternator is replaced by one with electronic regulation built in one or both the ground wires are often throw out.
Then one from the engine to the body. I usually put it from one of the 4 M8 bolts fastening the engine side support to an M8 bolt in the inner wheel arch.
When an alternator is replaced by one with electronic regulation built in one or both the ground wires are often throw out.
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P. de R. Leclercq
Re: Alternator wiring
I don't understand this.
Current flowing through a small lamp would provide very little excitation current, and if it did provide decent current, the lamp would melt! The circuit is merely there to confirm that the output from the alternator is greater, in voltage terms, than the potential on the battery. This, by the way, explains why warning lamps sometimes glow when the headlamps are switched on: a diode (or more than one) has failed in the alternator which reduces the output voltage. A check with a meter across the battery with the engine running and the headlamps on, will show that the voltage is less than the specified 13.5 - 14.4V.
The alternators with external regulators had a separate terminal (marked "ex") for the exciter circuit, current being provided via a green wire. Of course with later alternators, this is done internally.
Incidentally, the other two terminals are marked "D+" which is the same "pole" as the output terminal feeding the battery, and "D-" which of course goes to ground.
Paul
Current flowing through a small lamp would provide very little excitation current, and if it did provide decent current, the lamp would melt! The circuit is merely there to confirm that the output from the alternator is greater, in voltage terms, than the potential on the battery. This, by the way, explains why warning lamps sometimes glow when the headlamps are switched on: a diode (or more than one) has failed in the alternator which reduces the output voltage. A check with a meter across the battery with the engine running and the headlamps on, will show that the voltage is less than the specified 13.5 - 14.4V.
The alternators with external regulators had a separate terminal (marked "ex") for the exciter circuit, current being provided via a green wire. Of course with later alternators, this is done internally.
Incidentally, the other two terminals are marked "D+" which is the same "pole" as the output terminal feeding the battery, and "D-" which of course goes to ground.
Paul
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Andy Craig
Re: Alternator wiring
Hi Peter, hi Paul,
I've just been to check the markings on the back of the alternator. The L-shaped plug has in it a thick red wire which goes down to the starter (where this connects to the alt' it is marked B+) and a thinner red/black wire which joins up with the main, insulated harness and goes back to the dash (this is marked D+ on the alt'). The lone, male connector located close to the L-shaped plug is marked only with +. There is a big, heavy black cable earthing from the adjustment side of the alt' to where the starter is mounted to the bellhousing. I ran the motor with and without the L-shaped plug in place and the voltage across the battery remained the same at 12.65v (which of course means the system isn't operating at all).
I presume the the thick red wire carries the generated voltage from teh alt' and the red/black wire goes to the light on the dash (which, of course I haven't yet seen lit).
I apologise for an insufficient grasp of electrics but i reckon with your help i can suss out if the alt' is actually working or not.
Andy
I've just been to check the markings on the back of the alternator. The L-shaped plug has in it a thick red wire which goes down to the starter (where this connects to the alt' it is marked B+) and a thinner red/black wire which joins up with the main, insulated harness and goes back to the dash (this is marked D+ on the alt'). The lone, male connector located close to the L-shaped plug is marked only with +. There is a big, heavy black cable earthing from the adjustment side of the alt' to where the starter is mounted to the bellhousing. I ran the motor with and without the L-shaped plug in place and the voltage across the battery remained the same at 12.65v (which of course means the system isn't operating at all).
I presume the the thick red wire carries the generated voltage from teh alt' and the red/black wire goes to the light on the dash (which, of course I haven't yet seen lit).
I apologise for an insufficient grasp of electrics but i reckon with your help i can suss out if the alt' is actually working or not.
Andy
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Andy Craig
Re: Alternator wiring
Hi Huib,
I missed your post before i left my last reply.
I guess the big black cable i mentioned is fine as an earth from the alt' to the motor but i'll need another one from the motor to the body - if there isn't one already there. I'll go look.....
Andy
I missed your post before i left my last reply.
I guess the big black cable i mentioned is fine as an earth from the alt' to the motor but i'll need another one from the motor to the body - if there isn't one already there. I'll go look.....
Andy
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Peter Cripps
Re: Alternator wiring
Paul,
My information comes from the Bosch 'Automotive Handbook', which goes into great detail on how alternators work (as you might expect). It is quite specific that the lamp provides initial excitation current.
Actually, not much current is needed, just enough to start the generation process. As soon as the rotor windings generate enough voltage to overcome diode drops, self excitation starts to take over.
If you're interested I can scan the relevant pages ... it's quite interesting reading.
Peter
My information comes from the Bosch 'Automotive Handbook', which goes into great detail on how alternators work (as you might expect). It is quite specific that the lamp provides initial excitation current.
Actually, not much current is needed, just enough to start the generation process. As soon as the rotor windings generate enough voltage to overcome diode drops, self excitation starts to take over.
If you're interested I can scan the relevant pages ... it's quite interesting reading.
Peter
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Andy Craig
Re: Alternator wiring
Hello all,
I've been to check the earth as per Huib's suggestion. To recap ; a thick black cable connects the adjustment nut-and-bolt to where the starter motor is mounted to the bellhousing. Close to this another thick cable shares a lug with another black cable (which turns out to be the -ve side of the battery) and is securely mounted on the crossmember.
As far as I can tell the cables are in good order and should earth fine.
Andy
I've been to check the earth as per Huib's suggestion. To recap ; a thick black cable connects the adjustment nut-and-bolt to where the starter motor is mounted to the bellhousing. Close to this another thick cable shares a lug with another black cable (which turns out to be the -ve side of the battery) and is securely mounted on the crossmember.
As far as I can tell the cables are in good order and should earth fine.
Andy