Alternator/Regulator Repairs- Spitfire Mark IV, TR-6 and GT-6 Mark III

May, 1971

In the interests of efficiency and to ensure that sufficient replacement materials are available for alternator/regulator repairs, Joseph Lucas North America Inc. have recently introduced a common rebuilt alternator, Part Number 23556/R, and replacement regulator, Part Number 37565, which can be used for replacing the 15 ACR unit currently fitted to these models.

Wherever appropriate, it is intended that where only the regulator is at fault, then only the regulator should be replaced under warranty. A labor time of 00.25 hours will be allowed when replacing the regulator only, with the alternator in position.

List prices of these components are:-

  • Lucas Part Number 23566/R Alternator – $50.00
  • Lucas Part Number 37565 Regulator – $11.80

and standard Lucas discount applies.

To facilitate these new arrangements, Lucas will exchange any new alternators currently in Distributor/Dealer stock for replacement rebuilt units, if these are shipped to their depots via Distributors, and appropriate credit for the price difference will be issued.

Warranty application on these units are as per new car warranty, with exception that any rebuilt alternators fitted after normal new car warranty are guaranteed for ninety days from date of installation.

The following are simplified check and replacement instructions for these repairs. 

Test Repairs

1. Ensure warning light works by removing ALL leads from alternator, ground brown and yellow lead and with ignition on bulb should light. If not check bulb and connections.

2. Ensure alternator delivers maximum output (16 ACR at 2,500 rpms. 34 to 36 amps. 15 ACR at 2,500 rpms. 24 to 26 amps) by inserting an ammeter in the main output cable at alternator on solenoid (leave ammeter connected throughout all tests) and partially discharging battery by leaving headlights on or loading with carbon pile.

3. If readings below maximum and depending on belt, battery condition and meter accuracy install new alternator Part Number 23566/R.

4. If NO charge, regulator must be checked, (using same ammeter connections) by removing plastic cover from alternator (2 bolts 1/2″ socket) and reconnecting leads (ignition on, engine not running) then connect a test light between battery positive + and the green wire terminal of the brush box. If no light – replace regulator only, Part Number 37565.

Replacing Regulator

Remove alternator and detach faulty regulator. Attch new regulator using both mounting screws and connect green and yellow leads to the same positions as previous. Disregard any other leads or connections.

Regulator Setting

Ensure battery in fully charged condition by connecting voltmeter across battery, (ammeter still connected) and run engine at fast idle until output reads less than 10 amps when voltmeter should read between 14.0 – 14.4 volts.

If voltimeter is unstable or figures outside limits, replace regulator.