Bob P. -- Ignition Switch Woes

[davids2toys]

I do and so does Patrick?

[patrickt]

Originally Posted by davids2toys

I do and so does Patrick?

Yes, and so does Patrick. Now, you have to remember that capacitors do wear out, though not too often. The easiest way to test your MSD capacitor is to to disconnect your battery and then hit your horn button. If you hear the horn relay click and the almost beginnings of a "toot" then you know the capacitor is holding a charge. That's also how you bleed the capacitor off before you do any work on your electrical system.

[jetblue69]

Yep, definitely need to bleed off the capacitor... As an electrical/avionics engineer on commercial aircraft I can tell you that if you don't do that with gas turbine ignition systems it WILL KILL YOU!

[patrickt]

And considering that most of our cars are sitting dormant 99.9% of the time, it just makes sense to disconnect the battery and bleed the capacitor off. That will help reduce cooling system electrolysis corrosion and, theoretically at least, extend the life of the capacitor. My positive cable to the battery is on a big knife switch, so it's very easy to disconnect and visually confirm it. Then I just flip the dash light switch on and leave it on. Not only does that bleed the capacitor off, but it also prevents the capacitor from spontaneously charging itself (yes, they really can do that). It's always best to leave a capacitor shorted. That really only takes a few seconds. Yep, that's a great bar-room quiz question to win a free drink: Can a capacitor really spontaneously charge all by itself? And for bonus points, how the heck does it do that?

[jetblue69]

Originally Posted by patrickt

And considering that most of our cars are sitting dormant 99.9% of the time, it just makes sense to disconnect the battery and bleed the capacitor off. That will help reduce cooling system electrolysis corrosion and, theoretically at least, extend the life of the capacitor. My positive cable to the battery is on a big knife switch, so it's very easy to disconnect and visually confirm it. Then I just flip the dash light switch on and leave it on. Not only does that bleed the capacitor off, but it also prevents the capacitor from spontaneously charging itself (yes, they really can do that). It's always best to leave a capacitor shorted. That really only takes a few seconds. Yep, that's a great bar-room quiz question to win a free drink: Can a capacitor really spontaneously charge all by itself? And for bonus points, how the heck does it do that?

Well, I'll leave that for someone else. I will recuse myself from the contest given my profession.