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MG MGA - Another new condenser

Having checked out the fuel system thoroughly, cleaning all filters in the process, I was convinced that my misfiring and lack of power would be a thing of the past. But I should have known better and paid more heed to Barney's site which says "90% of carburettor problems are electrical". I replaced the condenser this morning and, hey presto, the problem is solved ... but this is the 3rd condenser in the last 600 miles, so am I just being unlucky or is there something else that's making them fail?
Robert Sinclair


There is a lot of debate on whether condensers are polarity sensitive.
The answer is that some are and some are not, depending on the type.
There is endless information on this in Google.
Does your capacitor have any polarity markings?
Is you coil correctly fitted?
Is your car the original positive ground or has it been changed?
Coil terminals are marked + or - but some are marked SW (switch wire) and CB (contact breaker).

M F Anderson

The capacitors (condensers) used in vehicle ignitions are not polarity sensitive - only electrolytic capacitors of relatively high capacity are polarized.

Robert, why did you put a new capacitor in your distributor? Was it causing any problems or did you replace it just because that has been the convention, to replace the capacitor when replacing points? If the original capacitor was not causing any problems, I would suggest digging it out of the dust bin and putting it back in your distributor - then unless there is a problem that can be traced back to the capacitor, DO NOT change it out in the future. Small capacitors, such as used in the ignition systems don't wear out over time - they usually fail shortly after installing them, or they will last almost forever. This is especially true today. Ignition capacitors produced today are, for the most part junk and are getting worse.

I purchased our TD in 1974 and like all the TDs of the time, the capacitor was a solder in unit and I couldn't find a replacement, so the first time I replaced the points, I just shrugged and left it in place. Over time, I still couldn't find a new on and that original capacitor stayed in the distributor until some time after the turn of the century, when I switched the ignition to electronic. Even then, I put the breaker plate, with the original capacitor in my "on board spares" against the possibility that the electronic ignition should leave me stranded somewhere, at which point I am sure that the original brake plate with the original capacitor on it will get me home with no drama.

For more information on ignition capacitors and and the problems with the ones being sold today, see the article, Condenser Failure in Conventional Ignition Systems (Steve Maas) at: and the article: Conventional Ignitions in the Totally T Type - Issue 31. Cheers - Dave
DW DuBois

What you need is one of these,i made my first one when I was an apprentice nearly 50 years ago, just clip it to earth, and the cable to the CB on the coil, (- for negative earth cars, + for positive earth cars) you don't even to remove your distributor cap, its the quickest way I know to check a condenser,A.T

andy tilney

Thanks for your comments and suggestions, one and all. Just to add to what I said earlier, this all started about a year ago when I was having repeated ignition problems. Although I never managed to find out what the root cause of the problem was, I finished up replacing the coil, points, condenser (capacitor) and rotor arm ... which resulted in several months of trouble free motoring. Then one day the engine suddenly cut out and wouldn't restart. With the help of a friendly AA man we eventually identified the problem as the condenser, which we duly replaced after which she ran perfectly again. That was about 600 miles ago but the latest 'failure' was very gradual, unlike the previous experience, with occasional coughing and spluttering, rather total failure, which was why I didn't suspect the condenser to be the problem again. To answer your questions Mick, 'yes' the coil is fitted correctly and 'no' there are no polarity markings on the capacitor. Having now Googled the subject, there seem to be a lot of people out there who aren't fans of modern capacitors ... but sadly my original one is long gone, so I guess I'll just have to keep my fingers crossed and make sure I've always got a couple of spares on board. At least they're cheap!
Robert Sinclair

It might be worth contacting the 'Distributor Doctor'

The guy is well known for his rotor arms and I bet he has a ready supply of quality condensers.

They may be dearer than most but then if you buy at a cheap price you'll almost certainly get cheap quality................Mike
m.j. moore

Robert - The other thing you might consider is to use a high quality standard capacitor as written in Steve Mass' article (linked in my original post above) that can be attached externally as pictured in Andy's above. If I ever decide to go back to a conventional ignition, using a capacitor, this is what I would use.

Something to consider by everyone with older cars - there is not a single car manufactured today (those that are mass manufactured) that use the old points style ignition that require the use of a capacitor - everything today is electronic ignition (and even that is fading into the past). The result, there is no call for quality ignition capacitors except for the minuscule number of old car enthusiasts like us - and we are quickly becoming the very small minority. Cheers - Dave
DW DuBois

I agree with Dave and it's the same with the point sets. One thing you can try is to make sure your distributor is well grounded. Many years ago my Dad who was a avid saltwater boater had a 302 Ford powered inboard. He started going thru condencers and getting stuck quite often. Center console boat did make the engine difficult to work on. Finally he pulled the distributor and found out it was corroded where the clamp held it to the block. Cleaned it up and never had trouble again. You could attach a seperate ground direct to distributor to the block somewhere and see if that cures it.
gary starr

Thanks again for all your comments and suggestions. I took Mike's advice and had a look at the Distributor Doctor website and found this statement there: "The quality of the commonly available condensers is very poor, in terms of both the physical fit & the performance /longevity. We have recently dismantled & examined 4 examples of the orange wired versions, from 4 different factories all around the globe, all of which are readily available & prevalent in the UK. The results confirmed our suspicions & why we are having so many phone calls from owners who've fallen victim to them. Original specification Lucas condensers & ours have 3 metres of winding inside, the orange ones have between 1 metre & 1.5 metres. The internal bonding & construction also left a lot to be desired. FIT YELLOW WIRE CONDENSERS"
Yes, mine is orange wired, but I'll be replacing it with a yellow wired one as soon as it's delivered.
Robert Sinclair

Hi folks, I'm following discussion with interest.

The other week while driving my A on the highway the engine suddenly quit (no misfiring, just quit altogether). Luckily I was only a couple of miles from home and managed to limp home with the engine quitting intermittently.

When I pulled off the distributor cap I found the condenser wire (orange) was burned - see attached picture.

I replaced the condenser with a NOS Lucas unit I've had sitting on the shelf for years (black wire). The car started straight up and idled perfectly. Then when I increased the revs to approx 3,000 the engine quit again. Rather than pointing the finger at the condenser I'm wondering whether is another problem - perhaps a short caused by the vacuum advance?

I'll definitely go Robert's route and purchase a yellow wired replacement but want some reassurance that my engine isn't going to quit again!

Any thoughts as to what else might be causing my problem?




Steven, I don't know the answer to your question, but I know a man who probably does. His name is Martin Jay and he's the Distributor Doctor referred to in my earlier post. His email is and his phone number is 0044 1984 629 540. Good luck
Robert Sinclair

Andy Tilney! You Sir are a genius!
I have never seen the "parallel condenser" trick before. Used it today for the first time on an E Type that suddenly wouldn't run..AND IT WORKED!!!!
You do get a bit of a shock through the condenser when clipping it to earth but it sure beats replacing the damn thing, only to find that it wasn't the problem.
A Bowie

Its best to connect it up first then try to start it,you are right you can get a bit of a shock from them when they are charged up, we used to charge them up on the spark plug cleaning machine, then shout to someone and throw it at them, so they would catch it,we used to make allsorts of things for testing stuff,another good one was a cly leak tester,which we made, using a spark plug a hydrolastic suspension valve, and a tyre pressure gauge, it works just as well as my snap on one I use today, AT
andy tilney

Mate you need to write some of this stuff down, with pictures, for us youngsters!
A Bowie

Perhaps you are right, I am off on holiday tomorrow for 3 weeks,i don't have time today as I am checking my car over ready for our trip, when I get back I will hunt all these things out and take some pictures and post them on here, A.T
andy tilney

This thread was discussed between 05/09/2015 and 11/09/2015

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