Cutout bench test

[k8207418]

I’ve got a cf3 and a CFR2 cutouts I need to bench test
I know there is a couple of basic tests that can be done but can’t remember how

[Stuart Giles]

You can do a few tests with a meter that reads Ohms. put a meter lead on the dynamo input terminal of the cutout, put the other lead to the cutout's earth. You should see a resistance reading somewhere around 60 Ohms for a 6V cutout. If so, the voltage winding is good. Leave the meter lead on the Dynamo input terminal and put the other on the cutout's output terminal; there should be no reading. if you manually close the cutout's contact, you should now see a very low resistance reading -no more than a few Ohms; this tests the current winding and points. If both these tests are good, you should have a working cutout.

[k8207418]

That’s great
Is there a test where you power up a couple of terminals and it snaps shut ?

[Stuart Giles]

That’s great
Is there a test where you power up a couple of terminals and it snaps shut ?

You can do this, but you really need a variable power supply to test it as the cutout shouldn't snap shut until you have a bit more than 7 volts

[k8207418]

Which terminals ?

[Stuart Giles]

Which terminals ?

Input from dynamo and cutout earth. You'll be testing the voltage coil as in my first post.

[k8207418]

D and E
Operates fine with the higher voltage ov a battery charger
Many thanks

[David Stepney]

The cutout works as follows: As the dynamo starts to charge, the field winding voltage rises, energising the voltage coil ( the coil with fine windings) which has one side connected to the field windings of the dynamo and earth, the resulting magnetic field overcoming the light spring holding the points apart. As the points close, current from the dynamo armature energises the current coil which carries current from the D terminal on the box to the A terminal and to the ammeter and thence to the battery. This further magnetic field increases the force holding the points shut. As the dynamo ceases to charge, current from the battery starts to flow back to the dynamo through the current coil. This reverses the magnetic field opposing the field created by the voltage coil. This reversal, together with the spring tension, overcomes the voltage coil field and the points spring open.

Both coils have one end connected to the D terminal on the cutout. The D terminal of the dynamo is wired directly to the D terminal of the cutout. The F terminal of the dynamo goes to the ignition/charge switch which, on winter setting, connects the dynamo field windings directly to the D terminal on the cutout, and on Summer setting, directs the field current through a resistor before it goes to the  D terminal.

To test the cutout, first connect an ohm meter between the D and E terminals on the cutout. You should get a quite high reading of about 50 to 60 ohms. This shows that the voltage coil is intact. Next, connect the ohm meter between the D and A terminals. You should have infinite resistance. Now manually close the points, whereupon you should get a low reading of about 3 to 4 ohms. This proves the current coil in ok and that the points are not burned and thus have high resistance. Now, assuming that these test prove ok, apply a voltage of at least 7 to 8 volts (I use 12 volts from my battery charger) between the D and E terminals. The points should close.

If the points are burned a light rub by passing a strip of fine emery paper through them two or three times should clean their surfaces up.

Hope this assists.