P1800 electrics

In the middle of trying to resurect a '67 P1800S, on hooking up the battery, I noticed blue sparks / flashes from the terminal as it made contact with the battery. Hmm, suspect a short somewhere. I spent a long time checking all the wiring and practicing weird yoga like positions under the dash. I have removed anything defunct or non-standard and repaired any frayed connector ends, wiring, etc. I then changed the starter which was dead, turned the ignition and hey-ho away she turns (just on a flat battery). However, the sparks persist at the terminal still present when hooking up battery. The voltage then drops pretty rapidly and drains the battery almost completely after 20 mins. Fresh battery on, I now check the terminals at the ignition switch eliminating the wiring behind the dash and find that the big red conector, the furthest away from the off position is the culprit, sparking when in contact with its connecting bolt. Hmm. Tracing it down the loom back to one of the large brown wires on the fuse box next to the dynamo regulator side and disconnecting it means nothing from starter, dash, etc, (horn still workes) but no battery drain / sparks. Reconnecting it, all works, but battery drains again and sparks come from the brown wire connector. Got as far as I can on my limited knowledge of car electrics. Can anyone shed any light??? Gordon

Disconnect the other wires in turn from the fusebox until you find the other one that sparks... the current going in from your large brown one must be going out again somewhere. Continue similar procedures until you find where it's ending up... Mind you I have a suspicion that the throwout coil in the regulator isn't doing its job - perhaps the contacts have welded themselves together. So you could try checking the regulator for stuck contacts and the like, or disconnecting the wires going to the dynamo and seeing if that stops it... I'd expect the dynamo to get a bit warm as well after the battery's been discharging through it for some time; I must say I have a job to think of anywhere else you could dump all the energy from a charged battery in 20 minutes without something catching fire, and I'm a bit surprised the dynamo isn't smelling.

been there 

I have a short cut on my old land rover who i cant find. Fitted to much new electrical (dims) on it and lost track. I advice you to invest in a small multimeter who mesures volt and other electrical resistance. Then you can losen every contact on the fuse panel in turn and the meter will give you direct readings on what happens. Then you will find the source faster and correct it. One thing i would have checked first is that the right wires are at the right points on the starter and the dynamo. The loss of power on the battery says that it is a large whire who causes the shortcut, a small wire will have melted at once. The electrtical system can also catch fire if its tressed so be carefull. Rune.

Probably a daft idea but perhaps its the cigarette lighter jammed in and cooking itself. I was trying to remember which wire under the dash ,think its black. If it didn't pop out and continued to heat no doubt there would be a bit of a wiff and it could probably drain the battery fairly quickly. just a thought mind, ian

Problem solved... 

Thanks everyone for you help. After replacing the regulator (the main culptit) and the coil (worn at the key end), the car fires up and runs fine without any niggles even over a long period.:Banane32: Only issue is what I suspect to be a leaking rear crank seal (oil leaking from the bottom of the bell housing) and some heavy smoking under revs which is probably the piston rings as the car was left standing for some years before the previous owner attempted to start it.:Dancing_unhappy: Have a great weekend. Gordon