2.5 V8 Dynamo, Regulator

[Clive]

Hi Stewart,

I have bought very cheaply original RB340 regulators from auction sites. They generally only require clean up of the contacts to be fully working, and they are well constructed.

I have used this Lucas document to get them working to spec: https://www.mg-cars.org.uk/imgytr/pdf/lucas.pdf. This document covers fault checking the generator.

Once you understand what the three coils do, they are not difficult to diagnose. You only need a voltmeter and ohm meter. (Yes you need an ammeter to set max charging current, but you can use the cars guage to do this.)

The charging light will come on if there is a bad earth connection to the regulator, so check the connections at both ends of the earth wire. A bad connection will prevent the cut out relay from connecting the generator to the battery.

The Lucas manual will tell you how to test the generator output to make sure it is functioning. They are not difficult to pull apart and refresh if needed.

Let me know if you need any more help pinpointing the issue.

Regards,
Clive.

[sumptners]

Thank you Clive for your helpful response.
Today is the first chance I have had to remove the Dynamo. I had new brushes to fit and upon removing the old brushes the wire to one was in the hole but loose and just pulled out. I have cleaned up the Dynamo and checked the terminals.
The terminal also and connections to the regulator were clean but all have been checked.

As I stated earlier the problem only occurs after a drive when the under bonnet temperature warms up.
Later in the week will take for a good run to see if we have success.

Thanks again for all of the helpful advice.

Regards
Stewart

[sumptners]

Hello and many thanks all who have posted helpful responses.

At the weekend I had a chance to give the car a good 40 mile run and I am pleased to say that the charging behaved impeccably. Good but not excessive charging and red light coming on at tickover and going out correctly.

Many thanks
Stewart
L

[classiclife]

Excellent, Stewart, well done - nice to have another job ticked off the list !!

Regards.

Richard.