Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Positive to negative, pros and cons

Working on a 54. This is a frame up resto. I am now working on the wiring. The car is currently a positive ground. So here are some questions:
1) Would you change the car to a negative ground?
2) Would you put in an alternator or keep a generator?

Thanks,
Ben

This comes down to a choice of originality over function. Personally I would change it, but buy one of the modern alternators that are assembled into a retro looking dynamo casing.

My personal choice if doing a comprehensive restoration would
entail retention of original specifications/components if at all feasible.
Only one man's opinion however.....

To me, it depends on what you are going to do with it once it's finished.

Drive it - then convert to alternator, doing as Deano suggests
Show it - then keep it original
Sell it - then keep it original

The only other factor that comes to mind would be if the car has individual historical significance, in which case keep it as original as possible.

Agree with what Tim said.

Positive earth is a pain. Just about any bit you add to a car is or expects negative earth.

I'd convert like a shot, one bit of originality that makes no sense and cannot be seen either as without a voltmeter, you'd never know.

Interestingly to note, all Morgans until the early 30s were negative earth. Then the fad for positive earth came in on most if not all manufacturers, Morgans included. I don't know if it is true, but my father said it was an anti-corrosion measure, although since it didn't work, and negative earth is much more convenient, manufacturers eventually reverted.

+1

Ben

Tim and others are correct. If you want to drive the car and enjoy ownership then use an alternator (whether you use one that looks like a dynamo or not is entirely up to you) Only use a dynamo if want to show or sell it, and even then convert to negative earth.
Using an alternator will commit you to negative earth (ground) . This will also give you a lot more choice of electric fuel pumps, and certain other accessories, positive earth versions are becoming very hard to find now.

Another vote with Tim. Can't even add anything, other than this thread has also been historically informative.

Thanks for all the input. Since this car will be a driver not a 'trailer queen' I plan to convert it. I will keep the original generator and the voltage regulator so if the next person wants an original, they can convert it back.

I will be going with an alternator rather than a generator. I think it will give me more options, such as driving lights and a radio.

So now on to the hunt to find parts and try to make it all look original.

Ben

Good luck Ben and don't forget post pics and tips as you go along.

Here's one supplier of alternators which resemble dynamos- but I'm sure there are others.

http://www.autoelectricsupplies.co.uk/product_list/197

That looks like a great source. I see that there is a regulator built in and I assume also a rectifier as the output would appear to be DC. Saves a lot of hassles.

I would imagine that you would also need to change your starter motor and possibly the wiper motor unless it is possible to run in either positive or negative earth. Another item to check would be the fuel pump if it is an electric pump. If the wiper motor and fuel pump are two wire, positive and negative, you would have to be very careful to change the connection correctly.

PS. I wondered if I was correct in thinking that the starter motor would be polarity sensitive. Perhaps that is not the case. I found this site which refers to changing polarity on an MG A. http://mgaguru.com/mgtech/electric/et202.htm
It seems to be a good guide and also mentions the electric tachometer and the heater fan. He has quite a bit of information on the electric fuel pump.

I also forgot about the ammeter which would have to be wired the right way round.

Ben,
My 59 and 61 Plus Fours are both positive ground, but I'll probably change to negative when the generators fail and I replace them with alternators.

Peter pointed out an important consideration: the ammeter also needs to be rewired. The ammeter is in an awkward place under the dashboard and it must be wired and insulated correctly. A friend of mine did not get the insulation right when he converted to negative, and it actually set off a small fire and necessitated a new wiring harness. A surprising amount of electricity goes to that little gauge.