Coil Wiring ?

Post by **PSL184** » Wed Nov 26, 2008 8:18 am

I'm confusing myself with this one so need a second opinion pls...

Car is POSITIVE earth

My old coil was marked "CB" which was connected to points
New coil is marked "+ & -"

Q - Which side is connected to points?

Post by **alanworland** » Wed Nov 26, 2008 8:53 am

Seems to me that the + should go to the points (and hence to the positive chassis)

Post by **alex_holden** » Wed Nov 26, 2008 9:45 am

alanworland wrote:Seems to me that the + should go to the points (and hence to the positive chassis)

I agree.

Post by **PSL184** » Wed Nov 26, 2008 9:50 am

Thanks chaps!

Post by **mike.perry** » Wed Nov 26, 2008 11:03 am

It will work either way round but whether or not it wears the coil out if its wrong I don't know.

Post by **PSL184** » Wed Nov 26, 2008 11:09 am

I had tried it both ways Mike and indeed it worked, although I remember from the past that you get a bigger spark if correctly connected?

Post by **Luxobarge** » Wed Nov 26, 2008 11:27 am

mike.perry wrote:It will work either way round but whether or not it wears the coil out if its wrong I don't know.

Yes it does indeed work either way, but the difference is whether the spark jumps from the centre of the spark plug to the little arm, or from the arm to the centre. I can't remember which way round it is, but one way gives a better spark, and more penetration of the mixture, and quite possibly less plug electrode erosion, so it is worth getting it right.

I also agree with above - +ve on the coil would go to CB on a pos earth car.

Cheers

Post by **bmcecosse** » Wed Nov 26, 2008 11:32 am

The 'way round' for the coil is to do with the internal wiring in the coil! And yes - you want the + sign to the points. But -you would be better changing the car to -ve earth, that was done for improved corrosion resistance. I can see no advantage staying on +ve earth unless you have an ancient trembler coil wireless in the car ??

Post by **PSL184** » Wed Nov 26, 2008 11:36 am

I will change it over at some point because I'll be putting a CD player in - but - 1 job at a time..... After the engine is finished I've got the 3.9 diff to fit, Wolseley brakes, front roll bar and radius arm kit... Then the CD player

Post by **mike.perry** » Wed Nov 26, 2008 3:53 pm

I believe the reason older cars were pos. earth is to do with the older type of fabric insulation on the wiring being more efficient as pos earth.
With plastic insulation it doesn't make any difference but you get less corrosion with neg earth.
Now tell me I'm wrong!!!

Post by **Leo** » Wed Nov 26, 2008 4:34 pm

Mike
I am sure there is good reason for the idea that negative earth produces less corrosion but I have decided to keep my 1954 Rover P4 and my 1969 Minor Traveller as positive earth, just as they came out of the factory.
Neither have shown any signs of major corrosion in all those years and the Traveller has never needed any welding repairs, so I see no reason to change

Leo (Wallingford)

Post by **PSL184** » Wed Nov 26, 2008 4:35 pm

Perfectly true Mike - The copper wire would act as the annode (or cathode - I can never remeber which way round) and consume itself because the fabric wasn't up to the job. I believe though, that only the very early MM's would be effected by this type of wiring....

Post by **mike.perry** » Wed Nov 26, 2008 5:48 pm

I noticed that the battery posts corroded more readily when the Series MM was pos earth and I had to clean the heater rheostat windings more frequently than since I converted to neg earth. I have since rewired the car with plastic covered cables.
The Traveller was fitted with an alternator when I bought it so has always been neg earth