Lack of charge

[David Morris]

Hi, the other day I experienced the problem of no charge from the dynamo on the Javelin we are re-building. I have had this before and spent many anxious hours cleaning and hopefully correctly adjusting the points in the regulator box. My usual solution is to finally give up and replace the RF95 box, which is horrendously expensive. This time, having the luxury of time in the garage, we took it easier and decided to be a little more scientific. First thing was to see if the dynamo was working. I connected a feed from A1 on the control box to the field connection on the dynamo and started her up. The result was a good charge! Thinking about this a bit deeper, if you are out on the road, a 'get-you-home' solution would be to fit a temporary jumper between the 'F' terminal on the box and 'A3'. This will put a full charge output from the dynamo. Watch out that you are not delivering too much charge shown on the ammeter, as you have shorted out the internal field limiting resistor, but this is better than no charge and should get you home, with the lights on if necessary!

My next job will be to rebuild a RF 95 control box. I see that YouTube has a video of someone rebuilding one, so I shall be watching that with interest!

All the best,

David

[BobCulver]

The get you home trick should be applied in short bursts to avoid cooking the dynamo or battery.
The quick test for dyanamos is to isolate and join the field and output wires and with a voltmeter or scrap headalmp bulb to earth voltage should reach 12 at modest revs and soar considerable above. A useful bench test using an electric drill to power.
The elecro mechanical voltage regulators are curious devices and surprisingly effective. Voltge is very steady. Analogue meters are usually inaccurate and digital do not like the car environment but can be used to calibrate. The setting is a bit of a puzzle but the voltage can be read in the car and tweaked to whatever considered appropriate ie 14.3 low load. Different verions of the same RF95 regulator are associated with particular dynamos as the max current differs.

[Keith Clements]

See this recent posting.