TR6 discharging

[Alan-64]

I have to charge the battery every few days now on my 1968 TR6 as the Boyer ignition dos'nt like the low voltage. The Ammeter shows a slight discharge when being riden. Is there any simple checks I can do on any of the comonents to eliminate them as the cause, or which order is recommeded for them to be replaced in order to cure the fault?

[L.A.B.]

First thing that I would suggest you do is to check the charge circuit wiring and its connectors, check the alternator stator wires where they connect to the stator as they can break at that position, or sometimes they get damaged by a loose primary chain?

Check the rectifier wire connectors are sound and also the wire connector to the Zener diode, and the earth/ground connections of both items are clean and making good electrical contact.

If it isn't a wiring fault (or a battery fault) then there are really only three things that can go wrong, the alternator stator, rectifier or Zener diode.
The alternator rotor can also lose magnetism after many years of use which can lead to poor charging, but this would not occur suddenly so the fault is likely to be either the rectifier or Zener diode I would think?.

Do you have a multi tester (to measure Amps Volts Ohms?)?      

[Alan-64]

Thanks for the pointers which I can get on with checking, and yes, I have a multimeter.

[L.A.B.]

I have a multimeter.

If you check the Voltage across the (fully charged) battery with the engine running I would expect to see approximately 14.5 V (lights off) and approx. 13.5 V (with lights on) when the engine is revved.

The rectifier can be checked after disconnecting the wires and using Ohms (x1). You should see continuity between rectifier the Neg. terminal and each rectifier alternator terminal with the probes connected one way, and infinity when the probes are reversed.
And the same result between the Pos. (stud) and the alternator terminals.

The Zener is a bit more tricky to test as a voltmeter and ammeter need to be connected and used together (more info given if required?). As a quick test you could try disconnecting the wire from the Zener terminal and see if that gives an increase in battery voltage when revving the engine? However ensure the system voltage does not exceed 16 Volts as it has a Boyer ignition fitted which could be damaged.