Technical ignition condenser problems

Went through condenser Hell a couple years ago with a brand new AC/Delco unit made in Mexico. Car would run, then not, then run again. Spent 6 months troubleshooting that one. Took the cap and rotor off one day, turned on ignition and pushed the points open with a screw driver; looked like a stick type arc welder in there. Put the old condenser in and no problem. Then later replaced with an Echlin uni-set and now keep the original stuff in the trunk just in case. I was blowing black soot out the tailpipes and the plugs were totally black but only had a few miles on them; junk now.

 

Yeah, if you're gonna run points, ya gotta do it right, no way around it. Condenser is a critical part, and the NOS are starting to show their age. They can and do go bad just sitting on the shelf. Testing requires several hundred volts DC to check for "leakage", most people don't have a way to do that. The parts stores mostly sell crap.

The OEMs used to sell kits to reduce RFI, they physically resemble an ignition condenser quite a bit, but they are not the same thing or capacitance/voltage rating. They went on the + side of the ignition coil, alternator or generature ARM and VR.

I vaguely remember some guy in the neighborhood who worked the night shift at a factory and he'd leave for work in the evening at the same time every night and his car would knock out television reception for several seconds as he drove by. Increased my vocabulary a little bit thanks to dear old Dad.

 

Noise suppressor . For radio I think.

 

Forgot the decimal point so no need for torches and pitchforks, lol...

 

36 C is same as 96.8 °Fahrenheit ( , converting the number for USA readers ). Also excessive heat can cause electronic component early failure.

 

Aaaaw, and here I just found my pitchfork. All dressed up and nowhere to gather an angry mob. Oh well, maybe next time!

 

This might be a silly question for those that know the answer...will any 12v condenser work, or are they application specific?

 

Just about any condenser will work (for either 6 or 12 volts) as long as the capacitance is in the correct range. I have found this range to be quite large. When developing my "trash can" condensers, I ran one as low as .047 micro-farads and it worked successfully. (I don't know about point life, though.) I have seen condensers form .20 microfarads up to .45 microfarads. (The latter were large, metal condensers I was told were designed to be used on transit buses.) The rating of the condenser depends on multiple factors, the most important of which are coil inductance and engine speed. Most modern coils work best when a condenser in the low .20's micro-farad range is used. The old Mallory "trash cans" and the Vertex magneto condensers currently available are higher than this.

As long as it physically fits and is not defective, just about any condenser will function adequately.

 

Thanks.

 

It looks to me like the problem is the manufacturers are finding it difficult to make a high voltage DC capacitor (condenser) that fits in a small enough package of the classic metal canister design (under the distributor cap). Ignition service is rough duty, too.

Difficult at a certain price point anyway, they can't do it when sold by the pound or by the sea shipping container or whatever. It wouldn't bother me to pay $10 if it was a good 'un.

You can "roll yer own" using high voltage "civilian" capacitors, but they aren't used the way once were, even when Radio Shack was still around they had stopped carrying that sort of thing. The more specialised electronics jobbers like Mouser and others still carry them.

If I were gonna run points I'd probably skip the parts store el-cheapo condenser roulette and use one of the Tubman condensers, or a 600 or 1000 volt poly film cap.

You'll note in the catalogs or onlime there are cute little modern very compact chiclet-gum looking metalised spray-film high voltage capacitors available that appear to meet every voltage and capacitance spec, but these won't work either. The Model T guys figured this out a while back, there is something called d/v rise time, that must be met to work in ignition service, kind of like current rating I expect.

Anyway you'll note a modern poly film capacitor of sufficient voltage rating and capacitance and d/v rise time and the rest of it will be fairly large and chunky. 1000 volts would not be "overkill" necessarily. @tubman have you guys figured out if 400 or even 600 volts is OK?

I tested a whole passle of vintage igntion condensers, some NOS and some junk box pulls, and some golly knows where they came from, and while they "passed" most of the basic tests perfect it sure looks like they are all defective in terms of insulation resistance or leakage when several hundred volts DC are applied, and that's what happens with ignition. I didn't bother to heat them up either (both ignition coils and ignition condensers need to be tested at normal operating temperatures).

 

We went with the largest capacitor that would fit in our "classic" packaging. They are rated at 650 volts and 250 degrees (another important consideration). I have sold over 300 of these without a "comeback" and the one in my '51 is a pre-production prototype that's been in there since 2016. Interestingly, we tried making a .33 microfarad version of the "trash cans" with the capacitor from the same family as the .22's we are using. I never had one last over 800 miles. They have similar ratings for temperature and voltage, but after 3 premature failures (and the realization that just about anything will run just fine on .22 or .33), gave up on that version.

Also of interest was thread posted here by @squirrel, where he dissected several failed current condensers and found that the external lead was not directly fastened to the "guts" of the unit, but just held in place by the crimp that holds the whole thing together. It is my guess that, with vibration and expansion from heat/cool cycles, these units lose connectivity and fail. Once the engine is turned off, connectivity is established again. Thus a condenser can test good, run for a while, and the suddenly fail, only to test good again when removed from the vehicle.

 

Racer, Somewhere in my junk I have these laying around. If I can find them, and if they fit your application, I would gladly send you one to try.

 

I count 8 in that pic,,,,maybe you will be able to find them,,,,,LoL .

Tommy

 

In some electrical circuits a little bit of capacitor "leakage" is acceptable. I don't know about ignition service, but I doubt it.

What I noticed in testing these things the junk box condensers or NOS they don't "hold" the charge for more than a second or two. One of the tests is applying 500 volts DC and looking for "leakage". The original old school condensers are now "duds" I think.

The modern high voltage capacitor sitting on my work bench, now that SOB bit me real hard the next day when I went to pick it up. Woke my ass up. LOL!

I'm not sure what happens with excessive voltage leakage in ignition service, at a guess something like spark quality at the plugs would be degraded and the condenser itself would start to get excessively hot and go open and kill the ignition entirely, or maybe intermittent.

 

I think the ignition system can tolerate some continuous leakage a lot more than it can tolerate a momentary open circuit...which is what the crappy construction results in.

 

I've got a OT 50cc twostroke bike, supposed to have a small 12V battery but I got tired of replacing dead batteries after each winter so I replaced it with a pair of 22 000 microfarad capacitors (got them for free). The dash has three 1,2W warning lights that light up every time the ignition is turned on, the capacitor only keeps them lit for about a second, it drains fast under that load, but it does it no matter if the bike has been sitting for a day or three months.

In other words, good capacitors can keep a charge for a LONG time. Something you want to keep in mind if you open any mains powered modern electronic device with a switch mode power supply, they rectify the input and charge a capacitor, for our 230V that capacitor is charged to 325V, the peak value of the AC sine wave (230V * square root of 2). Even if the device has been disconnected for days you may get a very unpleasant surprise if you start poking your fingers in the wrong place.

 

kind of like the "capacitor" that is the anode of a CRT? My dad told me when I was young, about poking around in a TV set, to make sure to discharge the high voltage lead to the side of the picture tube, before it zaps you....

 

CRTs work at several thousand volts, so greater zapping potential there. I'm sure you don't want to make that mistake twice.

 

Ex television repair guy here. I did it as an after school and weekend job, as I was a geek, not an athlete. The flyback transformer in some of the larger televisions generated a sawtooth wave in excess of 25KV at over 15KHz. The CRT is pretty much a perfect capacitor, as the insulator between the electrodes is solid glass, so leakage is non existent. They can hold an eye-reddening charge for a very long time. We made it a habit to discharge them any time we worked on one. They could throw a quarter inch spark a month after they were turned off.

 

Yup. My dad mentioned to me his foray into Home Television Repair. This would have been the 1950s or 1960s.

Mom: "You shouldn't do that" (dad with screwdriver in hand removing rear cover)

Dad: "It's unplugged!" ("What the hell does she know about TVs?")

He said it knocked him across the room, and all she said was "I told you so".

 

There is a guy (jon g) on the Stovebolt Forum that is making condenser replacements. Look on the Electrical Bay forum at the thread "Alternative Condenser Update". I have an 85 V8 Ranger that was a condenser killer. His unit put a complete stop to the failures.