Bosch alternator problems

Hi there,
after a jump start because of a flat battery,the alternator light on dash is on all the time
I've read somewhere that the rectifier diodes may have blown.
Does anyone know if it's a diy job to change the rectifier on a Bosch alternator ?
I can use a solding iron if that's whats involved
Thanks if you can help
Nige

Probably best to search the UK VWT4 forum. Here's an example of replacing the brush/diode pack on a specific Bosch model - not sure if it's exactly the same as yours, as you don't specify a part number.

[You must be registered and logged in to see this link.]

Hi  

You’ll find differing views about whether it’s worth repairing your own alternator but I hate the idea of spending hundreds (possibly) of pounds on a new or recon alternator if the original only has a simple fault.

nigel1947 wrote:I've read somewhere that the rectifier diodes may have blown.  

In my experience it’s normally only one of the main diodes that fails and that leads to a low output rather than complete failure and the warning light only glows faintly. There are other things that could cause the problem (slip ring, brushes, regulator) so I’d advise taking the alternator apart, inspecting everything and measuring the diodes before you do anything else.

nigel1947 wrote:Does anyone know if it's a diy job to change the rectifier on a Bosch alternator ?

Not sure about your particular alternator but I’ve had at least three diode packs fail over the years and all have been reasonably simple to replace. The pressed in types can be a bit of a pain but not impossible and you can often get the complete unit (at extra cost of course).

I remember in one case I took the wires to the outside and mounted a single diode on the back of the alternator, it lasted for years like that.

Brod.

Thanks for the info and advice, it's happened at a bad time as I'm off on hols this weekend (not in Topaz), but i'll let you know how I get on.
I've had a quote for £278 for a new unit or £130 recon so I think £37 for parts is worth a try.

Nige

As per Brodco, it almost certainly isn't the rectifier but the regulator. If it looks kind of like this:
[You must be registered and logged in to see this link.]

Then it's really easy to change - just two screws. Quite likely the brushes are just worn out. The recifier is a bit more of a job.

BTW, if you do need a new one, don't pay that much. Look here:
[You must be registered and logged in to see this link.] to start with. Don't know if that's the right van though.