Down to Earth

By Mark Garfitt

(With earthly guidance from Derek Smith)

Returning from my VSCC monthly “Last Thursday” Noggin & Natter at the Royal Oak Inn, Much Marcle, near Ledbury, Herefordshire in my faithful 319, FMC 119, the headlights began to surge before finally the dreaded ignition warning light shone bright red. My passenger asked ‘what does that mean?’ I informed him that it meant the dynamo was not providing enough to charge the battery and that we would have to press on. Coming up behind a truck travelling at about 60mph west along the A449 towards Monmouth we tucked in behind on sidelights to save our battery. He had the audacity to turn off the road so we had to use our own headlights. To cut a fairly long story short I dropped my passenger off at Usk and travelled the last 10 miles on quite well lit roads and there was a bright moon to boot before putting my car and myself to bed!

I had a spare dynamo with a voltage regulator riding piggy back so I changed the whole unit in about 20 minutes the following day only to find that I still could not extinguish the ignition warning light. Electrics are not my strong point so I rang my friendly auto electrician, Tom, in Newport, on Bank Holiday Saturday morning. To my surprise he answered the ‘phone and to my even greater surprise he suggested I bring the car down together with the ‘spare’ dynamo to his workshop, and so I did. He put the spare unit on his test rig and it all worked fine. I then swapped the dynamo/regulator from my car and he put this on test, needless to say that worked too! Heads were then scratched. Tom suggested that I had a wiring problem. I first checked the earth wire between the regulator on the dynamo and the mounting cradle. Normally the dynamo relies on an earth being made between the dynamo body and the cradle when held down tight by the strap. Because we like to have such items looking smart we keep them well painted and as a consequence well insulated which is just what we do not want. For some years now I have had a separate wire from the dynamo to a taped hole in the cradle to give a definite earth (Highly recommended that you all do it!) In this case it was fine.

I changed the dynamo over again and the ignition warning light went out – great, but why? Four miles up the road there was a bright red light again! At this point I rang our now retired electrical guru Derek Smith. “Sorry to disturb your Bank Holiday but I am in trouble”. I relayed the above story to him. “You have an earth problem” came the reply. I also remembered that even when the ignition light was extinguished you could still see a slight glow in the middle. First I was to check the main battery lead earth to the chassis. I did point out I had no problems starting the car. “Check the battery terminals and where the cables are attached to the clamps. Check also the main feed from the battery to the starter connection and when doing that make sure the supply wire from there to the ignition circuit has a good joint”. In fact I heated that up with a soldering iron to make sure I did not have a ‘dry joint’. The main earth wires were not just cleaned but smeared with Holts No-Corrode (an old tube which may not still be available!) Upon starting the car the ignition light, you are right, went out straight away! Interestingly the slight glow within the extinguished warning light that has been a feature for some considerable time has now also gone too. Thank you once again Derek. A rider to this article that he felt I should stress was ‘what a well thought out indicating device the ignition warning lamp is’, interpreting what it is trying to tell me is perhaps my problem!