P2 dynamo overcharging

[bill heywood]

My Rover 16HP P2 seems to be OK for about 20 miles and then the ammeter goes to full charge. If I freewheel then the ammeter shows a slight discharge, but as soon as I accelerate it goes back to full charge.It does not blow any bulbs and it does not appear to have damaged the battery in any way. Does anybody have any experience on this topic or any suggestions.

[luli]

The main suspect is the control box. The charging current is controled by a resistor in series with the field winding. A contacts set is switching this resistor on and off and determines the current. If the contacts are fused together the dynamo will generate excessive current. Often the remedy is cleaning the contact set. If this fails, there are firms which can repair the control box, or replace its "inside" with modern solid state control circuit. See diagram and more information here:
http://lulisml.files.wordpress.com/2011 ... ulator.jpg
http://lulisml.wordpress.com/2012/10/06 ... 9D-%D7%91/

[Chris C]

Attached is a link to a Lucas Technical Information regarding Regulators etc.
but it does sound as if there is a problem with the contact points.
http://www.justbrits.com/Articles/Lucas05.pdf
Generally when cleaning the points, if you use very fine wet & dry, make sure that
you clean the surface of the points to remove any fine particles of grit. Better to
use a very thin needle file. Rgds, Chris C.

[lakesrally]

If you cannot fix it Bill contact Philip Benson, auto electricians in Kendal. He is very sympathetic to our age of cars.