Classic cars forum & vehicle restoration.

MVPeters · Joined: 28 Aug 2008 Posts: 822 Location: Northern MA, USA

Ray & others!

I still don't think the cut-out is operating quite as it should. You're getting just a 6.5V trickle charge where 7.2V would be preferable.

You might like to watch this short video:

https://www.youtube.com/watch?v=kxK4GaK1wNg

Your Voltage cut-out units may not look the same, but they work the same way. You should get the general idea!
You may not have an adjustment screw & if you do, it may be on the top; or there may be just a 'tang' to restrain the contact.
Either way, the adjustment is minute - 1/8th of a turn of the screw or a tiny, tiny tweak of the 'tang' will be enough to start with - about the thickness of a piece of paper.
_________________
Mike - MVPeters at comcast.net
2002 MINI Cooper 'S'

47Jag · Posted: Tue May 22, 2018 11:32 pm Post subject:

Ray,

I second Mike’s comment re the 7.2 volts. You should see 7.2 volts across the battery with the engine at 1500-2000 rpm. Connect your voltmeter between the cut-out input terminal and its output. There should a zero reading (IE no voltage drop) if the points are in good condition.

However it don’t quite agree as to the function of the adjustment. The only adjustment on a cut-out is the actual voltage the points close at (the cut-in voltage) This will be around the 6.2V mark. It has no effect on the dynamo output voltage, that’s the 3rd brush’s job. If you can get the dynamo to put out 7.0 to 7.2 volts then all should be well.

Art

Ray White · Joined: 02 Dec 2014 Posts: 6304 Location: Derby

I have a suspicion the cut out gap is too wide. I will check it out.

On these vintage cars like my Dodge Brothers (1926) there is no automatic voltage regulation other than the reverse current cut out. Any adjustment is done by moving the third brush. I suppose it is why they recommend you set it high and switch the lights on 'dim'.

I set the dynamo output so as to read a positive charge while the engine was on tick over. I had a problem with the (correct) dynamo that I bought from the States despite it having been restored by a specialist. The third brush adjustment is quite neat with a tiny rack and pinion operated by a screw from outside the unit. Unfortunately, someone in the past had presumably forced it and the pinion had broken. I am enclosing some photos which clearly shows the damaged wheel and how I fixed it with a blob of solder. Not pretty but it worked.

As a matter of interest, when I first got my Austin Swallow (many years ago) I discovered that the CF1 cut out / regulator (single bobbin) had failed. The short term answer was to connect a length of heavier wire from the dynamo terminal on the cut out to the ignition switch. This "hot wire" regulator worked well enough but you had to remember to disconnect the battery when charging it and to never leave the ignition left switched on for too long. The short term fix lasted 20 years until I eventually had the CF1 unit restored!

MVPeters · Joined: 28 Aug 2008 Posts: 822 Location: Northern MA, USA

Yes, Art, you're correct if that cutout unit is a very early one.

The third brush on the dynamo needs to be moved a little bit to get 7.2V.
_________________
Mike - MVPeters at comcast.net
2002 MINI Cooper 'S'

Ray White · Joined: 02 Dec 2014 Posts: 6304 Location: Derby

I had a call from Alpha Batteries yesterday. They said the battery was faulty and would be replaced under the guarantee. I hope to get it delivered and soon be back in business. In future I will trickle charge on a regular basis so I am considering fitting a plug in point for a solar charger which I found works well enough on my Range Rover.