MODELS: All Models Equipped With Alternators; Negative Ground Only
SUBJECT: Fluctuation of Ammeter Needle/Ignition Warning Light In Models Equipped With Negative Ground Alternators
On cars equipped with Lucas 10AC or 11AC alternators and having NEGATIVE ground systems, some owners may report a condition where the needle fluctuates or the ignition warning light flickers. This will only occur under light electrical load conditions (i.e. in daylight with no accessories in operation) and can be immediately overcome by applying an electrical load such as switching on the headlights.
This condition will only occur when the battery is in a full charged state and is in no way detrimental to the functioning of the alternator charging system. If, however, an owner is insistent on immediate action being taken, first be sure that there are no bad connections in the circuit between battery and CI terminal on the 4TR control and from negative on the 4TR control to ground. Refer to WSM 149, Section N, for diagram and location of snap connections, etc.
If the fluctuation continues after this service, then the 6RA relay should be replaced. Be sure that the new unit, part number 1800746, is date coded 1/67 or later.