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Boxer Alternator Light
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Posts: 4From: Eden PrairieRegistered: Feb 2002
Lsand007
Junior Member


Friday, May 21, 2004 7:26 PM

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I have a 1979 Boxer.

When the key is off, the alternator red warning light is on. This is the same whether the trickle charger is hooked up or not. When I start the car, the red light goes off and the gauge operates in the "0" range, or slightly positive.

Any ideas what is up with this?

Lee

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512BB # 27001
President, MN FCA Chapter


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Posts: 1202Registered: Dec 2001
BillBadurski
FCA Technical Chairman


Saturday, May 22, 2004 4:58 AM

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Lee,
This is typically caused by a failed diode. There are six in the alt. You'll need to split the alt, then check each one individually. Use an ohm meter, and ensure they conduct one way, block the other. You'll find one that is probably conducting in both directions, or open circuited in both directions.

Delco diodes are a suitable replacement if you can't find Marelli. Only difference is the Delco is about .002" smaller diameter, and since these are a press fit, you'll want to sort through an alternator rebuilder's inventory to select one of his largest, as they do vary a bit in size.

With one diode failed, the machine cannot develop full power and eventually the battery will discharge with continued use of the car.

-------------------------
William V. Badurski
FCA Technical Chairman


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Posts: 4From: Eden PrairieRegistered: Feb 2002
Lsand007
Junior Member


Saturday, May 22, 2004 5:06 AM

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Bill

Thanks for the reply. In the Boxer I think this will be an engine-out repair?? Ouch.

I may just try to drive as is and keep the battery trickle charged. In Minneapolis it is a short season and having it in the garage during the summer is bad.

Regards,


Lee



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512BB # 27001
President, MN FCA Chapter


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Posts: 1202Registered: Dec 2001
BillBadurski
FCA Technical Chairman


Saturday, May 22, 2004 6:02 AM

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Lee,
I'm not sure about your particular car, but when I owned a 365 Boxer, this could be done with the engine in place from under the car. A bit difficult, but not impossible. Even had to change an alternator at the track once, and it was not too tough. I'd give it a try before chancing a dead car at an inopportune moment.

By the way, the diodes are in groups of three, positive base and negative base. When you find the failed one, you'll need to determine which group it's in. The alt rebuild shop can help identify if need be.

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William V. Badurski
FCA Technical Chairman


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Posts: 49Registered: Nov 2002
jimmyr
Member


Tuesday, June 08, 2004 5:37 PM

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Lee,

If the alt light stays on and the battery does not rapidly run down, it may be one of the smallest (trio) diodes. In any case if you are not familiar with alternator rebuilding, best bet is to locate a local automotive electrical rebuilder. These units are straight forward and much like all Bosch products.
Taking the unit out yourself as Bill described, will save you the most money, rebuilding is the least expensive of this repair.

-------------------------
jim riff


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Posts: 1Registered: Jul 2010
proximity4
Junior Member


Saturday, July 03, 2010 4:29 AM

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Battery Maintenance.

Battery maintenance is not something that is done very often by me. Until one day I decided to check the battery fluid levels. I read somewhere that battery levels can diminish quite rapidly.

When taking the filler caps off, checking at the front was not a problem, but the others were. Due to the overhang of the engine compartment fittings, It is not possible to see the filler hole levels at the back. I came up with this solution, which is probably familiar to most people.

Using Distilled battery water from a Motor factor, not tap water. With a flexible extension pipe battery filler - I made up a plastic bottle. Fill the back cell first, until you see the fluid just overflowing, empty the filler, squeeze the bellows, allow the bottle to suck up the surplus, then empty it into the second from the end filler hole. Do the same with each cell aperture.

Try not to allow the water to overflow as it has an acid content and will soon show up on the battery tray, and cross member, by rusting.

A Battery Filler, part Ref: 14900, can be obtained from: Vehicle Wiring Products, complete address below.

Checking the battery. Start the engine, with your test meter. The battery voltage should increase slightly from a nominal 12.5 v fully charged battery, when the engine is idling, and depending on the load on the battery. As the revs are increased then the voltage reading will rise up to a maximum of around 14.5 volts, if the alternator is operating correctly. Over 14.5 volts or a fluctuation in voltage at steady revs above idle, indicate a faulty voltage regulator in the alternator.

The Alternator

A simple way of testing this alternator function without a voltmeter is to watch the brightness of the interior reading lamp betwen idle and around 2000 rpm. It should brighten as the battery voltage increases when the alternator is producing a charge current.

A fully charged, healthy battery with no load (headlights on, etc.) will still be trickled charged and showing around 13v about 0.5v above nominal battery voltage when engine is ticking over.


I have included below for the interest of the DIY mechanic, details of the Alternator. Connectors can be seen on the drawing 'Alternator Contacts' and the internal workings can be seen in the drawing 'Alternator contacts Internally'

On the B+ contact can be found the heavy cable to the battery, usually covered in RED insulation. Often there is also a heavy cable to the starter motor at this point.

The D+ cable, in the Boxer covered with a BLUE insulation, is the cable which is used for the Fridge voltage control when the vehicle is running.
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