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Patrick · Posted: Tue Aug 30, 2005 12:16 pm Post subject: Alternator voltage regulator

Hello!

I'm having a huge electrical problem on my 33 1.7 i.e (1992).
The symptoms are:
1) No power from battery (I suspect it is not charged at all by the alternator)
2) Alternator low charging current light on the panel not working
3) When the car is jump started also at idle speed the alternator seems to give very low power and the car dies after a while if you do not increase the throttle

From my point of view this points to a faulty voltage regulator on the alternator (any other hints are welcome of course)

So my question is: Is the voltage regulator on the later models with BOSCH alternator (1992+) an external unit or an integral part of the alternator itself? If the second should be the case, can I repair anything without replacing the whole alternator?

Any other checks I can do to check that the regulator is really the cause?

Best Regards

Patrick

paulhide · Posted: Tue Aug 30, 2005 2:28 pm Post subject:

Are you certain that the battery ist in Ordnung
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done_fishin · Posted: Tue Aug 30, 2005 2:44 pm Post subject:

How old is the battery? If it is 3 years old or more the most likely suspect is the battery.
Do you have access to a Voltmeter? Check the Voltage across the terminals when the alternator is running .. should be around 14V.
Check both the terminals of the battery and the lugs, may sound stupid but you could have an oxide layer on the surfaces preventing the battery from charging, so check that the voltages are more or less the same, the more resistance the greater the difference in voltage between the two .. another clue to oxidisation is that the lugs/terminals get hot.
If it is oxidisation , clean up the surfaces of the terminals and lugs with fine grade emery cloth / wet'n'dry / sandpaper (just enough to get a clean surface) then give a layer of Petroleum Jelly or Vaseline to the surfaces then refit. The addition of the Jelly / Vaseline will help stop new oxides forming and maintain resistance free contacts.
If You have a lot less than 14 Volts you will have to check back towards the alternator to see where you either have bad contacts or lack of alternator output.
DON"T disconnect the battery to check the output from the alternator unless you have another GOOD battery to put in its place .. the voltage output from the alternator can go to around 35 - 45 volts , doing serious damage to whatever is connected and working on the car electrical system.
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gritsop · Posted: Tue Aug 30, 2005 3:19 pm Post subject:

Hi,

Does the battery turn the starter motor freely without hesitation? if the battery voltage is less than 12V then the motor won't turn and you will hear the relays clicking and poping. This is a clue to see if the battery is near dead or cranking the engine at low speed.

If we take the fact that the battery is new and it cranks slowly the engine then go for the oxidation tracking of the earth strips.

Hope this helps.

Regards
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
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ZeNiTh-PbArM · Posted: Tue Aug 30, 2005 10:26 pm Post subject:

Hi

Before you start replacing anything i would suggest that you unplug the connection at the back of the alternator ; there is a small wire (and two big ones) leading to this plug ; ground the little wire with a paper clip in the connector and switch ignition on : if the battery lamp in the dashboard remains silent you have a burnt lamp or a poor connexion somewhere in the lamp circuit.
this is critical since the current flowing through the lamp is supposed to allow the alternator to start.

besides the regulator can be exchanged quickly (2screws at the back of the alternator).

Best regards,
zp

Patrick

Hi!

Thanks for all your replies. Ì solved the problem for now....

First I checked the lamp in the dashboard - seemed to be ok but i changed it for a new one anyway.
Then I looked at the wiring diagram of the alternator/battery circuit - There are two fuses in the main fuse box for that circuit - Nr. 15 and Nr. 17. I checked both of them and as they were ok (maybe a little corroded) I put them back in.

And surprise,surprise the car started again without problems - really strange - could a corroded fuse connection create such a big voltage drop that the power of the battery is insufficient to start the engine?

Nevertheless the warning light on the dash does not come on anymore even not the first seconds after starting. But i check suggestion of isolating that little wire on the alternator connection...

Thanks again

Patrick

gritsop · Posted: Wed Aug 31, 2005 8:13 am Post subject:

Hi,

On Bosch alternators the warning light should come on upon starting. It will go out only if you rev above 1300-1500 revs.

It is normal for these alternators.

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop