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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 - 'Emergency' Condenser

I had the third condenser in eight months fail yesterday. At least I think it was the condenser. So I'm getting a little gun-shy and looking for a fast "emergency" roadside fix to put in my tool box to use when it happens again.

I read a post by Sandy Sanders in this thread:
http://www2.mg-cars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=8&subjectar=8&thread=201007112031024474

He said that he had attached a condenser to the low tension lead on the coil (to the distributor) and the case of the condenser to ground - and that it allowed him to finish a 250 mile trip.

Was that just luck, or will a condenser work when hooked in parallel with a defective one?

If so, then it sounds like a spare condenser and a jumper with a couple of aligator clips is all that I need for an "Emergency Condenser." Suggestions?

Thanks,

Lonnie
TF7211
LM Cook

Lonnie,
Why not just get a complete unit? ie condenser, points, and the plate that they mount to? It's only held in place with two small screws into the dizzy bowl..

SPW
Steve Wincze

Lonnie, the answer is 'YES' and 'NO'. 'YES' if it's a case where the condenser is an open circuit. 'NO' if it's shorting. To be safe, disconnect the faulty condenser before connecting in the replacement. Bud
Bud Krueger

Lonnie

I carry this part plus the two small screws that hold the plate in. I always seem to drop on of them. They are tiny. I carry that and a feeler gauge or new book if matches. On all my cars that use points that is in my standard. It is probably cheaper to just have items you mentioned but my method covers all issues.

I too read about the back up but never tried it.

Joe


JWP Policastro

Is it just me or did these old condenser seem to work better and last longer?




JWP Policastro

It looks like there is only 1 good supplier of condensers Standard products / Echlin. They have a low level & premium, RR175? / RR 174 or RR 176?
Len Fanelli

> Steve and Joe - A breaker plate with points set at .015", a good condenser, and extra screws (Moss 323-021) makes sense. Guess I'll go that way. However, I'll purchase the breaker plate without the points and condenser. (Moss 152-900) Don't want another Moss 163-900 condenser.

I'll still carry an "emergency" condenser with aligator clips because it only takes a couple of minutes to hook up and be on the way to a better place to do the repair.

> Bud - I guess the MG gods heard my plea about the same time that you replied. The new condenser that I installed this morning failed this afternoon within four blocks of driving. I limped back home (pop, bang, bump) and jumped the condenser with a different type hooked up with aligator clips as I described earlier. Ran like a champ with both condensers in series. I removed the extra condenser and the car bumped and popped again. Guess the bad one failed "open."

> Len - Based on my limited experience, looks like there are more bad condensers than good on auto parts shelves. The Standard/Echlin condensers that you mentioned require a new mounting hole in the breaker plate. I tried to find one with a mount that would fit my existing plate. BWD G635 is the ONLY one that I found.

The one that failed yesterday was a Beck/Arnley Condenser 172-5829 for an MGB.
http://shop.advanceautoparts.com/p/beck-arnley-condenser-172-5829/18026432-P?vehicleIdFromReq=-1&isAllVehicle=true&vehicleIdSearch=-1&searchTerm=172-5829&showTitle=
I backyard-engineered a mounting clip for it. Worked fine for the last few months.

The one that in installed and immediately failed today was a Moss 163-900. I had another Moss 163-900 fail even faster about six months ago ... just sitting in my driveway right after installation.

I installed a BWD G635 condenser this afternoon after the Moss 163-900 failed.
http://shop.advanceautoparts.com/p/bwd-condenser-g635/3031810-P?vehicleIdFromReq=-1&isAllVehicle=true&vehicleIdSearch=-1&searchTerm=g635&showTitle=
It is for a 1978 Plymouth Arrow and sometimes listed as also for an MG T-series. It has the same mount as the Moss condenser, but is about 1/3 smaller. It fits my breaker plate without modification. After I installed it I drove the car for about ten miles this evening and all is well ... so far.

I guess this brings me back to the question that I posted in May about needing an item number and local source for a condenser that will fit my TF without altering the breaker plate.
http://www2.mg-cars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=8&subjectar=8&thread=2014050700495825157

Thanks for your help and comments.

Lonnie
TF7211
LM Cook

I bought a cheap chrome plated coil off ebay, stuck the cheapest condenser I could find on the side, added a ballast resistor and opened the plug gap to .035" and enjoyed a hot spark for our supercharged toy for thousands of miles with no problems.
JRN JIM

Lonnie, please excuse me if it seems as if I'm being very flippant, but I'd love to know how you connected the repair condenser 'in series' with the 'failed' one. The expected approach is that you would clip the repair one across the questioned unit. This is connecting it in parallel, not in series. If the old one failed 'open', it would not affect the function of the repair unit. Are you completely removing the 'old' condenser? I'm having great difficulty accepting this perceived failure rate of automotive capacitors. Bud
Bud Krueger

Bud -

You're not being flippant. I goofed. I said "parallel" in my original post, but my fingers didn't listen to my brain when I typed "series" in my later post. You are right, the two condensers were connected in parallel. Thanks for correcting.

Lonnie
TF7211
LM Cook

The last two condensers I've had fail failed shortly after being installed. I have stopped replacing the condenser with the points. After replacing two good ones with new bad ones, I've decided to leave them in until they fail. Just my $.02
David
D. Sander

I had several condenser failures.
Went to pertronix about 10+ years ago and no worries since. Still carry a plate points and condenser as a back-up, but have never had to use it. I have given it away 2 or 3 times to help another "T" and they have always sent me a new replacement after the fact.
David Sheward 55 TF1500 # 7427

Since the TD came into the family in the early 70s, it has suffered one ignition failure- the rubbing block broke off of a set of points. Many years ago I installed a Crane electronic kit, and later a Pertronix. I have experienced zero failures, and spent zero time on ignition problems. Yes, I carry a points plate ready to go. Unless you are showing the car in AACA or something, toss the points. Just my thoughts. George
George Butz

I have a new crane setup on the shelf waiting, but been reluctant to install it. I just like points. When Jeff rebuilt the 72s distributor I had him keep the point setup. That was in 2006 and it's still working fine. PJ
Paul S Jennings

I'm with David and George. I think I've had the Pertronix in there for about 10 years now and it has never failed. I still carry my old points plate along as a emergency backup. The only issue with the Pertronix was in regard to the height of the rotor and the carbon brush ( http://www.ttalk.info/Failure.htm ). Bud
Bud Krueger

The modern condensers do fail faster than the old ones. I use NOS condensers out of old Lucas boxes when possible. Recently a friend's condenser failed in his '48 TC. It was the original unit that came with the car. Darn thing only lasted 65 years. I have a NOS unit in my car that has covered a lot of miles over many years, still working.

Electronic ignition can work well, but so can points when quality parts are installed. In 25 years I have never suffered a points failure, but I have had EI units blow themselves up. The trick to making any type of ignition components last is quality parts, good connections, and keeping voltage where is it supposed to be.
Steve S

I should have mentioned the Blue Streak is the better one from NAPA/ Standard products/ Echlin.
I also replace only as needed, if the points are pitting badly, with a build up on one point & a erosion on the other point.
Len Fanelli

Completely lost in the electronic theory being discussed. From my background the points condenser is only there to stop the back emf generated by the points opening and closing causing the points to burn, pit and transpose material between the contacts.

I can explain ignition failure with time if the condenser goes short circuit, I cannot explain the failure if the condenser goes open circuit. Maybe I am missing something.

The value of the condenser has to be a factor of it operating in a "tank circuit" which consists the condenser, lead and point resistance, primary coil inductance and the voltage applied. Altering any one of those will compromise the condensers effectiveness to do its intended task and its longevity.
G Evans

Lost the plot in my previous post as have many others who believed the sole function of the condenser is to protect the points.

Researching the subject revealed the following contained in a post in "Yahoo Answers".

"The system of battery/ coil/ condenser/ mechanical points is the Kettering system.
The condenser in the Kettering system charges when the points are closed, via the primary of the coil.
When the points open, the condenser DISCHARGES RAPIDLY through the coil.
The coil is energised, the spark occurs. But also, the collapsing magnetic field in the coil produces a charge in the condenser once again, while the points are open. When this field has collapsed, again the condenser discharges through the coil, but this time (and any successive time) the voltage produced at the secondary is less. The circuit "rings" or oscillates without necessarily producing a further spark.
When the points next close, the condenser again charges via the (low) resistance of the coil primary, ready for the next cycle."

Interesting facts, never stop learning.

G Evans

Just in case someone wanted to make up an emergency coil and condenser, here's an simple illustration of the ignition system on my old Case tractor. The condenser is mounted on the coil bracket. The condenser in the distributor is disconnected and the high tension lead goes to the distributor, not a single plug. Alligator clips can be used for connectors. It works and cost practically nothing if you don't have a spare point & condenser plate to exchange. PJ


Paul S Jennings

G, your knowledge of theory is beyond many here. Indeed, the condenser is part of a resonant tank circuit with the coil. It does more than just prevent arcing at the points. Ever tried firing up the engine without a condenser? Bud
Bud Krueger

Thanks Bud you have confirming what I read and posted, I was always under the misapprehension that the ignition circuit would still function with the condenser removed.

Graeme
G Evans

That description from Yahoo Answers isn't quite right. when the points are closed, the current builds up in the coil, and, in a sense, it gets "charged" with a dc current. (Capacitors don't charge when they're shorted, in this case by the points!) Then, when the points open, you've got an inductor with current in it in series with a capacitor, which is a resonant circuit, so you get a blast of AC current in the coil and capacitor combination. The coil, which is really just a type of transformer, has a peak voltage of about 150V across its primary and it jacks that up to several thousand volts at the secondary, which is plenty to create a spark at the plugs.

The AC waveform drops off pretty fast, as the energy is used up by lighting up the plugs. But the first half cycle is a nice, strong pulse that does most of the work. Without the capacitor, or with a bad one, you would get a very fast high-voltage spike at the points, which would fry the points and die off too quickly to light the spark plugs effectively. So, yes, the purpose of the capacitor is not just to protect the points; it creates the right waveform for effectively firing the plugs.
S Maas

This thread was discussed between 01/09/2014 and 04/09/2014

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