The Stovebolt Site Forums The Shop Area The Electrical Bay Testing a condenser

After reading that a lot of new condensers are bad out of the box, I just tested a new condenser that I bought as a spare and it went to just over 5 and stayed there. I'm assuming that's borderline bad? I've been told ~4 is bad. I watched a video that showed their meter going to around 18 testing a condenser. I'm assuming I need to take the condenser back? Does 6 or 12 volt make a difference? The video I watched was on a 12v system.

How are you testing it? Digital or analog tester? What is the needle (or readout) doing when you connect the leads?

It's a digital. The video showed testing ohms so that's what I was testing with the meter set on 20m. I just got back in from the garage and I guess I answered my own question. I pulled the condenser off of my '38 which is a known good unit. It was my spare until a week ago when I put it in the car. It tested identically to the one I just bought so I'll just put it on the shelf and say all is good. I don't know where they came up with the reading they got in the video. Neither of mine were close to it but the engine runs good. Thanks for the reply. Below is the video in question.

Thanks for the link. I agree with you, by the way. I don't know where that reading came from. As long as yours is working ok, then you're good to go. The multimeter I have has a capacitor tester, but it is a very old one and I'm not certain they still build that into today's meters.

I think it does but I wouldn't know the proper way to use it or what the reading meant anyway.

An analog ohmmeter is much better for "testing" condensers than a digital would be. Neither one will be particularly accurate- - - - -the old-time Sun motor testers had a real condenser checker, but I haven't seen one of them in use in close to 40 years. With the ohmmeter set to around a 50 K ohm range, the needle will sweep toward low resistance, then move back toward the "infinity" end of the scale and stay there. There will be no way to check for leakage through the dielectric of the condenser as the primary voltage surges to several hundred volts each time the coil fires due to magnetic induction each time the points open and the coil fires.
Jerry

Using an ohmmeter to test an ignition condenser is suboptimal for sure. If the condenser fails the ohmmeter test, it is helpful and you can throw the condenser away. The problem is the condenser may pass the test but still be bad. Recently, I went to a friend who has one of those real condenser testers, HRL mentions. I took 8 condensers that I have collected from my various Chevys and my Diamond T. All tested OK with my analog ohmmeter. Two of them, however, failed with the real tester. Here is why. As HRL mentions, condensers operate at several hundred volts and it is at high voltage that they start to leak. So my friend set up his power source at about 500 volts and that is when the two showed considerable leakage with his instrument.
Kent

Thank you gentlemen.

The real condenser (condenser same thing as capacitor) testers used a high voltage source but also produced a lot more current than an analog volt-ohmmeter for measurement. Digital volt-ohmmeters have way too much input impedance (practically no measuring current). For a quick test, it's best to use the analog meter and switch to the low ohms range. Make sure the meter has a good battery. The reversing polarity ohm check across the condenser is a quick and dirty check for open (infinity reading) and shorted (zero ohms) conditions. The instantaneous deflection of the meter needle is the capacitor charging or discharging. To properly test the condenser, you need a meter build to test a capacitor/condenser. Today's digital meters, that also measure capacitance, will give a capacitance reading (microfarad etc.) but I doubt the meter is capable of generating a voltage high enough to determine leakage. I suppose a test circuit could be fabricated with a load, a source and ammeter but that's way too much work. It's much easier to round can the old condenser and buy a new one. From what little I have read, automotive condensers are typically between 0.25 and 0.29 microfarads (regardless of 6V or 12V battery) and no less that 600 volts DC (2X the operating voltage of 300 volts DC). The thing about the automotive condenser is that it's usually inside a protective metal can and it's made to withstand heat where the same value capacitor used elsewhere may not. The Mallory company is a name I think of (I'm old-school) when it comes to an American manufacturer. Maybe Bosch (German) is next. Anything coming out of China or Taiwan is an unknown.

In electronics school, we learned very quickly NOT to catch something somebody tossed at us. Most of the time it was a capacitor charged with several hundred volts off a power supply. ZZZZZZAAAAAAPPPPP!
Jerry

Dis is true. Don't ask me how I know.....

We used to charge them up and leave them laying around the shop. Sometimes on the floor and sometimes on the work benches. The newbies and custodial people had a deep rooted dislike for us.🛠