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PV, 120 (Amazon), 1800 General Forum for the Volvo PV, 120 and 1800 cars |
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Ignition problemViews : 1811 Replies : 20Users Viewing This Thread : |
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Apr 3rd, 2018, 09:10 | #11 | |
arcturus
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Addendum. found some on amazon .de. ordered two
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life's too short to drink bad wine Last edited by arcturus; Apr 3rd, 2018 at 09:34. |
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Apr 3rd, 2018, 10:10 | #12 |
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I knew I had seen it somewhere, just checked Specifications in Haynes 120/1800 manual and condenser capacitance is 0.23-0.32 mF. Not sure if that would be any different for a 6v PV system though. Hope this helps. Also just consulted a very good reference book I would recommend to all, 'Haynes Automobile Electrical And Electronic Systems' which says 'A capacitor used in an ignition circuit has a capacitance of around 0.2 mF.
Last edited by Underdrive; Apr 3rd, 2018 at 10:21. Reason: Extra info |
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Apr 3rd, 2018, 14:37 | #13 | |
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Yes, the C must “play” with the L of the coil. The combination is supposed to give a short electromagnetic “ring” in the circuit when the points open, the frequency of the “ring” depending on the values of C and L. But I think the mere fact that the “ring” happens is more important than the actual frequency of the “ring”. It’s a bit like a bicycle bell: the pitch doesn’t really matter; as long as it rings and people can hear it. I am sure 1.0 μF will also work. |
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Apr 3rd, 2018, 14:46 | #14 | |
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Are you sure there was good electrical continuity all the way from the condenser can to the car chassis, including between the condenser can and distributor body? Important, particularly if you run at 6 volts. What made you conclude that the condenser was the problem? Could it not be that the act of swapping condensers serendipidously resulted in changing the electrical continuity from bad to good, and had nothing to do with the condenser itself? |
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Apr 3rd, 2018, 16:00 | #15 | |
arcturus
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Apr 3rd, 2018, 22:15 | #16 |
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underdrive & Simon; ...great info from both of you...I haven't measured one yet, but given your info, would certainly also expect a value in that range...regarding failure mechanism, the (Bosch) one I had fail had worked fine without issue before an extended lay-up of a car, then, after re-commissioning, failed when trying to rev engine...idled fine, but broke down and shorted intermittently killing the ignition when trying to drive...that was a tricky one to find...I suspect ingress of moisture during storage compromising the dielectric...
Simon; I understand the "ringing" of Primary L and C based on values and max expected RPM...I would expect value to be less dependent on V of system...but, given these Ign systems are somewhat different (different R and L?) from more typical ign systems with Ballast resistors, do you have any insight or thoughts on what the C-value would be for one of those ign systems? Regarding corrosion on C connections on arcturus' vehicle...I hope with my constant preaching of "clean and tight connections, preferably treated with ACZP", his chassis connections didn't suffer from issues, but I do understand you had to ask... Cheers |
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Apr 4th, 2018, 01:04 | #17 |
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The ballast resistor systems, in the normal running condition (ie. with the resistor in circuit), look the same as a non-ballast system. The total series resistance of coil + resistor is about 3 ohms; the resistance of a non-ballast coil on its own is about 3 ohms. The inductance is the same for either coil. It does not, of course, make any difference whether the series resistance is all distributed or partly distributed and partly lumped. Therefore, both systems have equivalent L/R time constants, max currents, and energy storage; and both have the same requirement for the capacitor value, too.
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Apr 4th, 2018, 10:03 | #18 | |
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The clearing process can age the plastic so it fails prematurely although would still be out of its standard warranty following an extended lay-up. The capacitors are sealed with resin so shouldn't allow water ingress unless the resin is compromised or it was added on a damp day, sealing moisture in. Good call on the clean and tight connections too! I'm a bit late to this thread but having had a 144 about 30 years ago and suffered repeated condensor failure on that (duff components, proven on a digital Wayne Kerr bridge at work) it intrigued me. I think generally the standard of replacement parts has gone downhill largely due to things being made to a price, rather than a specification.
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Apr 4th, 2018, 12:47 | #19 |
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LS;
...good insight and info!...interesting, about the "clearing process"...I too have seen instances where the "test" process was so stressfull that it actually subtley (sp) compromised the product with "latent failures"...and this wasn't discovered until hard field failures started occurring later...investigations narrowed in on the test process as the root cause...a major ooops (expensive...recalls, etc.)! I expect that bridge instrument to measure C value and so not necessarily show a high voltage breakdown mode of failure (unless it has a test mode for that also), but you might elaborate on the instrument, and mode of failure you found, further... Cheers |
Apr 4th, 2018, 14:20 | #20 | |
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As far as i remember it, the condensor had gone open circuit and i had 3 similar ones, all from the same shop and brand. I replaced it with a Lucas one and problem solved so presumably a bad batch. As an aside, generally testing of any product can result in almost destructive testing and would certainly compromise some things out in the field. For example, something i learned about 25 years ago is when lifting equipment is tested to let's say, 500kg, they use twice that weight (1 tonne) and if it lifts and holds for a certain period of time, it's certificated safe for 500kg. Obviously that's a different kind of testing and there are so many different methods of testing various products to ensure they work to try and list them all, or even research them all would take an incredible amount of time.
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