Alternator strip down (1 Viewer)

Dec 12, 2010
5,368
21,182
Cumbria
Funster No
14,651
MH
C Class
Exp
since 2011
Stripped down a Bosch alternator off the Unimog as it wasn't charging the battery. Apart from it being full of dirt, one of the brushes had a section broken off it, although it was still making a slight contact with the slip ring. Do you think this would be enough to make it not charge or do I have to start checking the diodes (6 of them) bit out of my depth now. :(
20170302_144605.jpg
 
Jan 22, 2013
1,245
58,366
London SE
Funster No
24,385
MH
A class Adria vision I707
Exp
since 1971
it's bit of a. throw away society now! it's been at least 20 years since i last built an alternator, but the diodes are easy to check, you will have continuity one way and very little the other, did you have a glowing IGN light that grew slightly brighter when you rev the engine? if so that usually points to diodes,
to be honest it usually works out cheaper to have an exchange unit than rebuilding one,
if you had replaced the Stator/ brush assembly/regulator/bearings it would be more than an exchange unit without any guarantees,
 
Jan 22, 2013
1,245
58,366
London SE
Funster No
24,385
MH
A class Adria vision I707
Exp
since 1971
to answer your question that i overlooked no a chunk out of the brush shouldn't stop it working,

Subscribers  do not see these advertisements

 

Derbyshire wanderer

LIFE MEMBER
Mar 30, 2014
1,269
2,366
Derbyshire
Funster No
30,753
MH
C class
Exp
15 years
Those brushes look worn down to being almost making no contact to me.
Try Cargo Nottingham for a replacement set as an exchange alternator will still likely be in comparison an expensive repair
 
OP
OP
jockaneezer
Dec 12, 2010
5,368
21,182
Cumbria
Funster No
14,651
MH
C Class
Exp
since 2011
Thanks for the info guys, I thought I'd have a look first as the 'Mog is 41 years old and I wasn't sure about availability of parts.
I've just done a quick check of the diodes and I'm getting values of around 640 on all of them (give or take a little) and current seems to flow one way only.
The slip ring with the worn brush is grooved but should clean up on the Myford.
@Derbyshire wanderer, thanks for the info about Cargo, just emailed them.
Son has spent too much this month on winch and chainsaw spares so he's asked me to have a rummage around with it to see if there's a cheap fix.
@ivorantony, not sure on the light situation as the gauges are chaotic at the best of times.
I've seen a picture of this type of alternator with a capacitor pack bolted to the back, this one doesn't have one, would it just be used as a suppression device ?
If it all checks out, I'll be looking for a wiring supply fault I think.
 
Aug 6, 2013
11,941
16,532
Kendal, Cumbria
Funster No
27,352
MH
Le-Voyageur RX958 Pl
Exp
since 1999
If that brush makes contact intermittent or high resistance you won't see an output from the alternator. In my view the brush is most likely to be the fault. The alternator works by whizzing a magnet around inside a 3 phase winding. The magnet is created by applying battery voltage, via the slip rings / brushes to the winding on the rotor. That supply is varied to make the whizzing magnet stronger or weaker and therefore the alternator output higher or lower. The alternator regulator is what monitors the alternator output then varies the supply to the rotor to stabilise the output at 14.2 (approx) volts. Depending on alternator type you will have 6 large diodes usually mounted on a heat sink and 3 smaller ones. The smaller ones provide an output for the Ignition Warning Light - or whatever it's called this week. Any canister-type devices on the outside are, as you suggest, suppressors.

Subscribers  do not see these advertisements

 
Nov 18, 2011
11,856
42,474
Planet Earth
Funster No
18,938
MH
A van
Exp
Over 25 year's
With a clean up and new brushes it should be ok if it's a diode there penny's of the internet there was me thinking I was the only one who refurnished old thing's
BILL
 

Snowbird

LIFE MEMBER
Apr 24, 2009
11,818
22,345
Liverpool.
Funster No
6,422
MH
Fifth wheel.
Exp
Since 11-05-2000
Have used Mark in Stoke for years rebuilding Alternators and starter motors. If you get stuck he charges me around £25 for a rebuild, and he has never failed to sort one out yet.
Broken Link Removed
 
OP
OP
jockaneezer
Dec 12, 2010
5,368
21,182
Cumbria
Funster No
14,651
MH
C Class
Exp
since 2011
That's the kind of info I was after guys. I was struggling a bit earlier as I have a little knowledge (but that can be dangerous !) I've ordered a set of brushes (£7.50) and will get new bearings seeing as I'm in there anyway (£7.20) and will skim the slip rings. The insulation on the various components seems ok, if it does the trick I'll be more than happy. Just need to hunt out my old solid copper soldering iron to remake the joints as I had to use a micro flame torch to separate them, even my gas iron wouldn't make enough heat to melt the soldered tags.
Thanks for the link to the sparky @Snowbird, always good to have a plan B. (y)

Subscribers  do not see these advertisements

 

Join us or log in to post a reply.

To join in you must be a member of MotorhomeFun

Join MotorhomeFun

Join us, it quick and easy!

Log in

Already a member? Log in here.

Latest journal entries

Funsters who are viewing this thread

Back
Top