MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - BR12 Coil

Anyone got a NOS BR12 coil for sale? Cheers.
Peter TD 5801
P Hehir

I have a nice kinda rusty original one that checks out OK with an ohm meter but I cannot guarantee it works OK.

The Moss ones are not bad. The only real issue is the lip at the bottom is not rolled and of course the date is not appropriate.
Chris Couper

BTW I use the Moss reproduction coil on my car. For what shows its very good. I doubt any concourse judge would fault you for it. Its a lot better than the tires I see on show quality cars.

You can see the coil in various pictures here (Engine Compartment Pictures):

http://www.mg-cars.org.uk/mgtd/mgtd_gallery_my_mgtd.htm
Chris Couper

Thanks Chris. Can you give me the primary & secondary resistance readings? Also is your original one a Q12 or a BR12? Because I'm fitting an EI I will probably need the BR12 because of its bigger spark.

Speaking of tyres, I know the original geometry was set up for crossplys but that radials are a definite improvement in the wet. It has been seriously suggested to me that on our cars crossplys handle better than radials! (Maybe I should start a new thread). Cheers
Peter TD 5801
P Hehir

Turns out all my coils are Q12's except the one non Lucas Sports coil.

They measure 3 ohm and ~8k ohm. One is a 53 and I think one is a 51 if you care about years and just want a Q12.

Not sure if they actually work though but not sure other than resistance how you can tell when they are not installed and running.
Chris Couper

I want to ensure I have the best possible spark using available original technology. This means using the BR12 (if I can find one). Researching coils, I found a thread on Google "MG TD TF 1500 - Coil Polarity" & tried to reactivate it. No luck. The search engine came up blank. One of the posts on that thread I found to be quite amazing! So much so I've cut & pasted it below:

O.K....
I'm about to "stir up a hornet's nest"....
Just recieved a printed article from a friend, that is the former president of a local car club...
He is one of the most knowlegable folks that I know, about antique cars....
The article is written by Donald M. Russell Jr., of Falmouth , Mass., o.k'd by the Technical Director of the Polytechnic Institute (not absolutely sure which State, sorry)...
Here's the quote that really throws me:

" Please note that the + and - coil terminal disignations, have nothing to do with the battery polarity. It has to do with the phasing of the coil magnetic windings. In transformer parlance, "-" designates the start of the winding, and "+" designates the finish of that winding.
.... if mechanics connect the (+)coil terminal to the distributor points, and the (-) coil terminal to the ignition switch, in a POSITIVE-ground car, it will result in an INCORRECT phasing of the coil."

He goes on to say:

"Why is connecting these terminals properly so important? If they are properly connected in phase, so that the back EMF in the primary adds, rather than subtracts or blocks the back EMF in the secondary, a substantially better, hotter spark will be obtained...usually up to 25% better."

Now, I know this is going to throw some folks for a loop, it did , me!

Discussion is about to get hot.
Edward
(E.B. Wesson)"

Seems like a great way to get something for nothing! The thread goes on to describe a simple test that can be performed to see if your coil is properly connected or connected "backwards". Check it out. Cheers.
Peter TD 5801




P Hehir

Peter,

Below is a description of how to determine if your coil is correctly connected. It is copy pasted from my response to this point in the archives in 2008.

Jeff,

I think that the best method to determine if your coil is connected correctly is to use a meter to look at the direction of the spark.

You need an analogue meter.

This is how to do the test.

Connect the negative lead of the meter to any sparking plug cap.
Connect the positive lead to earth.
Set the meter to the highest voltage range.
Turn the engine over, with the ignition on, try you prevent the engine from starting.
While cranking, you should see the needle jump.

If it jumps upwards the coil is connected correctly, you don’t need to read the voltage value.

If it flicks downwards, (against the backstop) it is incorrectly connected.

These instructions apply to both positive and negative earth cars.


John

52 TD


J Scragg

Thanks John. An extremely useful post from the same thread dealing with a very important piece of information! Cheers.
Peter TD 5801
P Hehir

Waaay back in the recesses of my mind I remember an instructor placing a common pencil in the gap of a magneto test machine that would show the direction of the spark. The pencil tip would show a trace in the direction. Lacking an analog meter (mine didn't survive the fall), I think it could be tested that way. If it worked on a magneto it should work on a coil ignition.
JE Carroll

Moss has these videos. There are a number of them

https://www.youtube.com/watch?v=e66tA43wsNo
Chris Couper

Attached is a photo comparing the sizes of Q12 and BR12 coils. Same general size and shape, but the BR12 is fatter.

Tom Lange
MGT Repair

t lange

Thanks Tom. When you see them side by side the difference is obvious. Anyone know if it's possible or ecomomically viable to rewire either a BR12 or a Q12? The major difficulty seems to be getting it apart without destroying it. (I'm looking for a bigger spark from the original container). Cheers.
Peter TD 5801
P Hehir

No, Peter, not possible - I have never heard of it being
done.

Keep looking on eBay - they do appear from time to time.

I'll also keep my eyes open.

Best, Tom
t lange

This thread was discussed between 19/03/2014 and 24/03/2014

MG TD TF 1500 index

This thread is from the archives. Join this live forum now