Dynamo

[Goldensyrup]

Got the bus out after winter and my light is on on my dash saying my dynamo isn't charging . Had a quick look yesterday and think it's dead.
What's people's thoughts on dynamos ? Should I swap to alternator ?

 

[Peter Good]

Very likely your dynamo is fine. However, having been laid up for a few months it has probably just lost its 'residual magnetism.' You will need to repolarise the dynamo; just do a search on here or a search engine for Dynamo Polarisation.
Peter Good
PS My advice is stick with your dynamo. The VW reputation wasn't built on the use of alternators. A personal view of course!

 

[Goldensyrup]

We tried that polarisation and the dynamo spun, but the lights still on on the dash

 

[sparkywig]

Are the brushes OK?
Is the regulator OK and all connections secure?

 

[Goldensyrup]

We are going to check both those bits tomorrow, so I take it that after we re magnetised it and it spun dies that mean the dynamo is good it may be the regulator

 

[atafonso]

Probably the regulator.

 

[Peter Good]

It could indeed be the regulator, but spinning the dynamo as if a motor only proves the basic copper windings are all in place and OK. It doesn't prove there is enough residual magnetism to start up. You really need to disconnect the regulator fully at the dynamo (make cable ends safe) use a piece of wire and short the DF terminal to earth/dynamo case, attach a 0-20 DC voltmeter / multimeter between the D+ terminal and earth and run the engine / dynamo up briefly. Assuming you have a 12 volt electrical system, the output from the dynamo should run up in direct relation to engine revs, and well above 12volts. Typically up to 20 volts or so. If you have an output then the dynamo is working OK, only then consider the regulator, if not some more action on the start-up is needed.
Peter Good

 

[Goldensyrup]

Thanks for the info, sounds like u know your stuff

 

[sparkywig]

Thanks for the info, sounds like u know your stuff

:lol:

 

[Goldensyrup]

All sorted thanks guys. Had a play about tonight and it was stuck brushs. Saved me a load of cash and time