Have you tested the various parts of an alternator?

macafee2 · 18th March 2023, 16:59

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 · 18th March 2023, 17:10

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

macafee2 · 18th March 2023, 17:54

Quote:

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 · 19th March 2023, 08:52

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 · 19th March 2023, 18:09

Quote:

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 · 19th March 2023, 18:38

Quote:

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 · 20th March 2023, 10:09

Quote:

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 · 20th March 2023, 12:06

Quote:

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?

/

18th March 2023, 16:59	#1
macafee2 This is my second home Rover 75 Saloon & Tourer Join Date: Sep 2012 Location: Lincoln Posts: 15,009 Thanks: 1,630 Thanked 3,032 Times in 2,181 Posts	Have you tested the various parts of an alternator? 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

18th March 2023, 17:10	#2
KWIL Precise Rover 75 Tourer 2.5KV6 Connoisseur SE Join Date: Mar 2013 Location: Fleet Posts: 2,977 Thanks: 630 Thanked 617 Times in 480 Posts	How did you test? Probes directly on the rings or via a brushes? Were the rings shiny clean?

19th March 2023, 08:52	#4
KWIL Precise Rover 75 Tourer 2.5KV6 Connoisseur SE Join Date: Mar 2013 Location: Fleet Posts: 2,977 Thanks: 630 Thanked 617 Times in 480 Posts	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.