My early mk3 is not charging - red light stays on and only about 12.5 volts showing at the battery when running. I have tried 2 different dynamos, both with new brushes fitted and the segments cleaned but no improvement. I suspect the control box but before buying a new one how can I check the output of the dynamo with a multimeter?
How To Check A Dynamo Is Working Properly
Started by
mister bridger
, Aug 06 2010 03:51 PM
6 replies to this topic
#1
mister bridger
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Posted 06 August 2010 - 03:51 PM
#2
dklawson
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Posted 06 August 2010 - 04:14 PM
See this PDF:
http://www.vintagemg...DFs/Tech103.pdf
If you determine a new control box is required, make sure you clean its contacts before placing it into operation. The "new" units available at this time have some form of protective coating on the contacts which must be removed if you want the charging system to work properly.
http://www.vintagemg...DFs/Tech103.pdf
If you determine a new control box is required, make sure you clean its contacts before placing it into operation. The "new" units available at this time have some form of protective coating on the contacts which must be removed if you want the charging system to work properly.
#3
mister bridger
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Posted 06 August 2010 - 04:17 PM
Thanks Doug, knew I could rely on you!See this PDF:
http://www.vintagemg...DFs/Tech103.pdf
If you determine a new control box is required, make sure you clean its contacts before placing it into operation. The "new" units available at this time have some form of protective coating on the contacts which must be removed if you want the charging system to work properly.
#4
mister bridger
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Posted 06 August 2010 - 04:30 PM
Well it failed test 2 so I presume that means a new dynamo needed, or are these things easily repairable?
#5
dklawson
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Posted 06 August 2010 - 05:25 PM
The Mini used the Lucas C40 generator. There are two body styles, a smooth case unit and a "stepped case" unit. The stepped case is what I've always seen on Minis while the smooth case seems to have been used more on Triumph cars of the same time. Functionally they are the same. There should be a lot of used ones out there in fair condition or you could have yours tested and rebuilt.
#6
bmcecosse
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Posted 06 August 2010 - 07:27 PM
To check a dynamo - disconnect the wiring, then join the two connections on the dynamo together with a bit of wire - rig a jump lead from earth to the case (if it's not on the engine) and then touch a lead from +ve to the joined up wires - the dynamo should run as a motor (make the fan belt very loose first!). If it motors - it's fine. If not - it's faulty. Simples !
#7
mister bridger
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Posted 07 August 2010 - 01:34 PM
Well I was about to buy a new dynamo but did this test and it worked as it should. One new control box from Southern Mini Days at Bewl Water and problem solved. Many thanks!To check a dynamo - disconnect the wiring, then join the two connections on the dynamo together with a bit of wire - rig a jump lead from earth to the case (if it's not on the engine) and then touch a lead from +ve to the joined up wires - the dynamo should run as a motor (make the fan belt very loose first!). If it motors - it's fine. If not - it's faulty. Simples !
Edited by mister bridger, 07 August 2010 - 01:34 PM.
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