Hi all, this is my first post and thought I’d start a new thread as I couldn’t quite find the answer in any of the archives.

I’ve got my ‘67 500F with the original 110F engine up and running for the season with a new Distributor, plugs and leads so I took her out to stretch her legs a bit, down a few miles to the local Italian Market (fitting, right?). Was running strong until about halfway there when she sputtered out and stalled. I rolled her into a shop nearby who jumped me and got her going and put her under charge for a bit while we tried to sort out the problem. Eventually found the generator wire had shaken off, therefore the car was running straight off the battery until she ran out of juice. Easy fix, new connector and I’m on my way.

Unfortunately, I was caught up in traffic most of the way and had to keep her revved at the stoplights and eventually I lost her again. A couple jumps later I get her back home (along with some prosciutto and Mozzarella) and put her under charge with the wall charger. After dark I went out and unplugged her and closed up the garage for the night but before that I started her up. Crank was strong and turned over normally. Now here’s the question:

1) Under idle, after the full charge, the Generator light is on bright. It fades when I rev the engine but comes back on at idle. Is this normal? I don’t remember that before.

2) What tools/gauges/instruments do people use to check the voltage coming off the generator to see if it’s where it should be to keep the battery topped off?

3) Do I need to worry about the battery being fried after getting discharged so much?

4) after sitting for the winter is it possible/likely that the brushes need maintenance?

5) suggestions on what to check first?

Thanks!

The owners manual I found on here states that the generator light will stay on until the engine RPM goes up over 1200. That’s consistent with what I’m observing. I’m wondering if I should keep the battery attached to the wall charger to get a constant trickle charge whwn not in use. Is this common practice?

Hi Steve as you have already discovered the generator light does have a tendency to flicker at tick over and then go out when the revs go above 1200rpm so that’s normal. The reason it is probably brighter after you have charged it, is because one side of the generator light is connected to the dynamo/generator output and the other side to the battery. So you may have 12V’s at idle coming from the generator and maybe 13V’s coming from the battery, so you have 1V potential difference which will make the bulb light up. The light will only go out when you have 0V potential difference across the bulb I.e. both sides are equal.

If you have a nicely recharged battery, then it’s a good chance it is going to make the bulb shine brighter, as the battery voltage initially will be higher than the output of the generator at idle, once the battery has been run down a bit it will only charge as high as the generator output, so in theory both sides will be equal voltage and the bulb won’t come on. The disadvantage of a dynamo over an alternator, is it doesn’t charge the battery at low revs, that’s why when you rev the engine the output from the dynamo rises to equal the battery output and the bulb goes out.

If your charger is a trickle charger as opposed to a normal battery charger that you would use when a battery is completely flat then yes leave it connected. A trickle charger isn’t designed to recharge a battery from flat. They normally have programs on them where they will condition the battery as well, so they go through different charging cycles where they will allow the battery to run down a bit and then recharge it slowly over a set period of time. My 500 is always connected to a trickle charger.

Tony

An important thing to remember about 'trickle' chargers---do NOT leave them connected, plugged in (to the power socket) but turned OFF---the battery will 'back-charge the charger and flatten the battery (over time). My experience of this is that my last 'full-time' job was a Col/Del driver for a Ferrari/Bentley and Maserati garage----I wish that I got a 'fiver' for every time I went to collect a car and the battery was flat, to the bewilderment (and annoyance) of the car's owner. Every time, I saw that the charger was still connected, still plugged in, and turned off! This was despite the fact that when we sold one of these (expensive!) chargers, we made a point of telling the purchaser that you MUST disconnect the charger from the battery when it was turned off. Captains of industry? I wouldn't let some them loose on a lake in a rowing boat!!

Quick update on this one. After ordering a battery tester which diagnosed the battery health at 28% - “damaged” I swapped out the batt for a new 51R (US size). MUCH better starting and idling. Seems draining the batt to zero a few times really did a number on it.

Now I’m trying to chase down why both tail/brake lights don’t work but the flashers do...