Control Box To Major Tom

[sloopjohnrb]

1962, 4 door 948 cc Screw type control box.

After a long run, came indoors for a cuppa, 10 mins later went out to start Gladys and battery totally flat.

I suspected the battery at first, so swopped with a known good and charged one, eventually same thing happened.
Checked wiring and dynamo, all OK

Obviously battery OK but not recieving charge, and that's when I noticed the obvious!!
The red charge light came on when revving high, went out on tick over.

In the control box, I advanced by one turn clockwise, the Regulator adjusting screw
and the red charge light glowed even stronger.

I turned it back to original posistion, and then in steps of one turn anti-clockwise, took it back an eventual 4 turns.
The red charging light is now out at almost all revs except the very highest.

Gladys has recently been in for some work and I think the Control Box/adjusting screw (s) might have been altered during investigative work and perhaps not put back to "norm" again.


Things seem to be going in the right direction, so please could you tell me how to set the voltage regulator screw, and, if applicable the cut out adjusting screw to the posistion they should be in.

Hope you can help
John

[mike.perry]

"Its never the control box"
Have you inspected the dynamo brushes and connections.
You should not fiddle with the control box unless you know what you are doing and have the correct instruments

[bmcecosse]

Oh it CAN be the control box - and now it has been 'adjusted' - anything is possible ! When the car was getting 'some work' - is there any chance the battery polarity has been reversed. But the first check - is the fan belt tight enough? Otherwise - dynamo check is called for. Do you know how to do that?

[sloopjohnrb]

Hello and thank you for your reply.

Right, Gladys has been in for an MOT (passed) and I asked if the electrics could be looked at at the same time as the battery had not been charging/or holding its charge properly.

The battery was checked and found to be good.

Fan belt is fine and properly adjusted and the dynamo checked and found to be OK.

I checked all the fuses, and then the screws onto the Control Box.
Nothing loose or untoward.

The reason I suspected the voltage regulation was due to the charging light getting brighter the higher the revs.
I have a standard volt meter, but I read that a moving coil volt meter is needed to set the voltage properly.
I wondered if vthere was an alternative way?
Best wishes

[mike.perry]

Forget about fuses, they have nothing to do with charging, they just protect the component circuits.
I would still inspect the dynamo brushes

[bmcecosse]

How do they KNOW the dynamo is ok??

[sloopjohnrb]

I would guess that the garage tested it using electrical test equipment...


I think I may have solved the problem.

Using the instructions in both the Workshop Manual and the Haynes, I tested the dynamo myself and found it was slightly below the best reading, as specified.

I then checked the Control Unit as per, and found I had backed it off a tad too far, it was kicking out around 12 volts.
Gradually I increased the voltage adjuster, a quarter turn at a time until it was kicking out 16 volts.

I then went back to re-check the dynamo and found it was juust about right, maybe a tad below optimum, which probably will be cured by a new set of bushes and a good clean.

Thank you again for all your advice and help.
I really appreciate it.
Best wishes
John

[bmcecosse]

16 volts is TOO HIGH!! 14 volts is ideal. You will fry the battery at 16 volts -and blow all the bulbs........ So just how are you 'testing' the dynamo -and deciding it's about right/slightly below ??? I'm mystified........

[sloopjohnrb]

Using the instructions in both the Workshop Manual and the Haynes, I tested the dynamo myself and found it was slightly below the best reading, as specified.

[sloopjohnrb]

[frame][/frame]

[sloopjohnrb]

[frame][/frame]

[bmcecosse]

Ah right - but that test will depend heavily on the precise revs which you can't know to any accuracy ......so just use it to indicate that it IS charging. But I repeat - 16 volts is FAR TOO HIGH - turn it down to 14 volts.