Here you can get How to Cleaning and replacing a control box.
On cars with dynamos, faults within the control box show up in various ways, a number of which are described in Testing a dynamo and checking output. Others may be revealed by the ignition warning lamp. If the lamp doesn’t go out as the engine speed rises, the cutout points aren’t closing. If the lamp glows dimly at low speeds and brightens as speed increases, the fault is perhaps dirty, oxidised or burned cutout points.
If the lamp goes out at an abnormally high (or low) speed, it’s going to be a symbol of an equivalent trouble within the voltage regulator points, or that either set of points is wrongly adjusted. The points are tricky to affect , and therefore the job should be entrusted to an auto-electrician.
Before you are doing that, check that the underside of the control box isn’t wet or dirty, which may sometimes produce the same symptoms. Many control boxes have resistors under the baseplate which, if short-circuited by dirty water, can allow overcharging. Clean the baseplate and terminals once a year, particularly if the control box is mounted during a place exposed to damp and dirt. Also make sure the lid fits tightly.
Removing the box for cleaning and fitting a replacement box are similar jobs, so follow the appropriate parts of the instructions. Do not buy a replacement control box until you’ve got made sure that it’s not the dynamo or the wiring which has caused the trouble; even then don’t fit it until you’ve got rectified any faults that would damage it. Be sure that the replacement is identical, or the approved successor, to the first . Boxes with different specifications may look alike, so check the model number.
Replacing a control box
Disconnect the battery before starting work. Mark the control box leads with the letters of the terminals where they fit, then pull them off or unscrew them. See that the connectors are sound and clean. The box is usually fixed by two or three screws, which can get over a rubber mounting; ot there could also be some quite other backing. Remove the screws and take off the box. take care not to damage the frail resistors mounted on its underside.
The backing acts as an insulator and seal ; confirm its keeping out water and dirt, clean the world under the box and therefore the box itself unless you’re renewing it. Refit the box, ensuring it fits snugly against its backing which the lid fits tightly. Reconnect the leads, then the battery. Start the engine and test the box.
Cleaning the control box
Wipe the underside of the box carefully; the resistors are easily damaged. Use a clean, dry cloth, or one moistened with parafin if necessary, to get rid of dirt. Keep paraffin away from rubber parts. Also clean the terminals employing a soft rag and methylated spirit. Allow the rear of the box to dry before re-fitting.