Have you tested the various parts of an alternator?

[macafee2]

Have you tested the various parts of an alternator?
Preferably one for a Rover 75.

After watching a YouTube video I thought easy but it seems not quite.

My first question is what resistance should be found across the two slip rings? When I measured, the reading just kept climbing, any idea why?

thanks

macafee2

[KWIL]

How did you test? Probes directly on the rings or via a brushes? Were the rings shiny clean?

[macafee2]

Originally Posted by KWIL

How did you test? Probes directly on the rings or via a brushes? Were the rings shiny clean?

On the rings. The rings are worn with definite grooves but no, not shiny clean.

macafee2

[KWIL]

That would suggest that the probes are not in constant contact and the variation may be due to changes in contact pressure on unclean surfaces.


When I rebuilt a spare alternator for my 75, I machined the slip rings to a very fine finish and also replaced the bearings.

[macafee2]

Originally Posted by KWIL

That would suggest that the probes are not in constant contact and the variation may be due to changes in contact pressure on unclean surfaces.


When I rebuilt a spare alternator for my 75, I machined the slip rings to a very fine finish and also replaced the bearings.

Ok thank I will try to give them a clean. The bearings seem fine.

macafee2

[dave lincs]

Originally Posted by macafee2

Ok thank I will try to give them a clean. The bearings seem fine.

macafee2

I thought you had now replaced your alternator with a new one?

[macafee2]

Originally Posted by dave lincs

I thought you had now replaced your alternator with a new one?

I have, the car is all back together and charging. I want to know what was wrong with my old alternator and can be repaired?

I can test parts, not sure about the rectifier but I do not know what measurements I should be getting.

KWIL has given me a pointer about the slip ring so will look at that tomorrow.

I have watched a number of videos on YouTube about how to test an alternator but they only go to "is it producing "12v" DC?", if no change the alternator but what about the voltage control unit, stator, armature and rectifier? These parts are not covered.

I was hoping someone had already done this and could
give me guidance. Hoping to get as much information as possible I have also emailed valeo.

If I can find the problem, brilliant, if I can go the one step further and fix it, even better, if I can help another member,
then it will go some way to covering the help I have been given.

I want to fix my old alternator, throwing it away is a last resort. I doubt I will throw it, just in case

macafee2

[macafee2]

Originally Posted by KWIL

That would suggest that the probes are not in constant contact and the variation may be due to changes in contact pressure on unclean surfaces.


When I rebuilt a spare alternator for my 75, I machined the slip rings to a very fine finish and also replaced the bearings.

I have cleaned the slip ring and tried again where the brushes touch and also on the edges where the brushes do not touch and still the reading for resistance goes up and up. The rectifier is still connected.

The resistance between the two rings seems to have climbed over 2k ohm. I have been spinning the armature as prat of cleaning the rings, could this be having any influence on the reading?

macafee2

[dave lincs]

Originally Posted by macafee2

I have cleaned the slip ring and tried again where the brushes touch and also on the edges where the brushes do not touch and still the reading for resistance goes up and up. The rectifier is still connected.

The resistance between the two rings seems to have climbed over 2k ohm. I have been spinning the armature as prat of cleaning the rings, could this be having any influence on the reading?

macafee2

I think you might have made a spelling mistake on this post but i could be wrong?

















































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[DMGRS]

If you do find you have any particular part that's worn, we have the slip rings, brushes etc here: https://www.dmgrs.co.uk/products/rov...-and-yle102500

When testing the resistance of the windings from the slip rings it should be stable - if it varies, you may well find the rings are worn through to the plastic core (as mine were at 170,000 miles).