View Full Version : New coils for old

09-02-2012, 07:24 AM
My TR3 came with a Lucas Sport coil and it is working fine, as far as I can tell. It's probably been on the car for 10 years.

Recently, a friend gave me a new Bosch coil for the car.

My inclination is to leave well enough alone and not replace the Lucas coil, but perhaps it makes sense to install the new coil. (I have no experience with Bosch coils.)

Any suggestions or recommendations?

09-02-2012, 07:34 AM
Everyone will have their opinion but I will quote an acquaintance of mine from another message board: "It's never the coil".

His message is/was aimed at the myriad of people who at the first hint of a problem replace the coil and "fix" the problem. Later they typically admit "oh I also replaced the points, condenser, cap, rotor, plugs and plug wires". They will still claim it was the coil when replacing all those parts at once.

That said, there are more occurrences of Lucas Sports coils failing than others I am aware of. However, yours being 10 years old will not likely be part of that recent quality issue. My advice, thank your friend for the Bosch coil. Wrap it in towels and carry it in the boot if you want to. But don't change your coil only because it is old. Age is not by itself a problem.

As for Bosch coils, like any other brands there are good and bad models. For a standard ignition, the Bosch Blue is very solid and dependable. It is what I have on two of our British cars. However, even within Bosch there are quality issues. Based on web site information it appears only Bosch Blues from Brazil retain a good reputation and quality. That's what I have purchased.

09-02-2012, 07:53 AM
I had a Lucas Sports Coil go bad after a year, engine instantly shut down and I coasted off the road. Had a gut feeling it was the coil since the shut down was instant and complete, got a ride home and back, put in an old coil, started up instantly without fiddling with anything else.

I think since your Sports Coil lasted this long, it is probably a good one but from my experience I would keep a back up in the car.

09-02-2012, 08:19 AM
Thank you very much for the input. The Bosch coil that was given to me is a blue coil from Brazil. So, I assume it is one of the better ones.

I will take your advice -- which I totally agree with -- to leave the Sport coil alone and cary the Bosch coil as a backup.

I really don't know how old the Sport coil is, but I have had the car since October 2009, and the fellow before me had it for about a decade (no evidence that he installed the coil)....

09-02-2012, 10:47 AM
Check to make sure that the coil you have is correct for the TR3. If your ignition is basically stock, it needs to be one that works without a ballast resistor. That means that the coil should measure about 3 ohms between the two small terminals. A ballasted coil measures about half that. You can always measure the coil you have on there and see what that reads. It should measure about 3 ohms.

09-02-2012, 10:49 AM
Everyone will have their opinion but I will quote an acquaintance of mine from another message board: "It's never the coil".
While I'll agree it's not the first thing to look at, I've had several coil failures over the years. Offhand, I'd say more coil failures than condenser failures, but at least roughly equal amounts.

When I put TS13571L back together, I kept the Lucas coil that was on it. Ran fine for about a year, failed during TRfest 2009. Didn't fail entirely, just started running _really_ bad. New points, condenser & rotor made no difference at all; changing the coil (Lucas Sports bought at the event) solved the problem instantly. I even put back the other old components, to prove to myself that the coil was the problem.

Less than 2 years later, the new coil also died! This one failed more completely than the first, but still not entirely : the engine would still run but not well enough to move the car. Oddly enough, it even ran sorta OK again once it had cooled. Again, I changed points & condenser first, no improvement; new coil solved the problem. (Actually it wasn't "new", that time I put back the old K-mart coil & ballast that had been on my previous TR3A before it got wrecked.)

It's wearing a Pertronix now, we'll see how long that lasts.

I've owned German cars before, I don't consider Bosch even as good as Lucas. So I have no experience with the famous "Bosch Blue" coil at all. But I did find a web page warning of various types of fakes:

09-02-2012, 11:22 AM
My late 59 TR3A has pos ground & a Pertronix ignitor ignition. What is the correct resistance for my coil.
Present coil is an off brand & works OK but I do not know what the replacement should be.


09-02-2012, 11:31 AM
My late 59 TR3A has pos ground & a Pertronix ignitor ignition. What is the correct resistance for my coil.
Present coil is an off brand & works OK but I do not know what the replacement should be.
Unless someone has added a ballast resistor, your coil should be around 3.0 to 3.5 ohms.

09-02-2012, 08:06 PM
Thankfully Randall I have only had one coil start to fail and it never left me stranded. I started seeing some unusual tach behavior and switching the other components did not address the problem. Swapping one coil for another I already had made the tach problem go away so the switch was done in advance of failure.

An honest-to-God Bosch Blue is about as solid a coil as you can get, literally. They are epoxy filled, not oil filled so they never leak. It is not unusual to see one 40 years old on a VW. However, it's not unusual to see a working Lucas coil that old either. It appears that only in recent years have there been problems with low quality ignition coils from several manufacturers.

The Bosch Blue will have a nominal resistance close to 3.8 Ohms. It is for "standard" ignition systems without the ballast resistor. I believe Bosch chose "red" for their equivalent 1.5 Ohm coil for ballast ignitions. The link Randall posted is a good read. It summarizes what to look for and why when selecting a Bosch coil.

09-02-2012, 08:42 PM
Jeff at Advanced swears by the Bosch Blue coils for whatever that is worth.

09-03-2012, 07:06 AM
Jeff/Advanced is where I bought my last Bosch Blue from. They are not inexpensive. Jeff's prices are as good as any place you will find.

09-03-2012, 07:27 AM
Actually, when I said that a friend gave me a Bosch Blue, it was not quite that simple. He said I should order one and he would reimburse me for it. I purchased my Bosch Blue from Jeff/Advanced.