12-19-2010, 08:14 AM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,025
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There's Always a Trick...
Chas., there's a trick that will occasionally fool you when doing a parasitic drain test. That special tool referenced in the GM Service manual is really not special at all; it's just a plain On/Off switch on your battery cable. But what it allows you to do is conveniently attach your multimeter in parallel before you disconnect the On/Off switch (thus forcing all current through the multimeter). This is a very important step in your parasitic testing. Here is an example that I thought up that will explain why. Suppose you have a dimmer switch on the light in your living room. If you run it all the way down so that the light is just barely glowing it will create a nice, romantic atmosphere. But if the power goes off, and then comes back on, the light will not come back on at that low level. You must then turn the dimmer switch up high, the light will come back on, and then you can dial it back down to the low level. The same can be true for a parasitic drain on your car. Removing your battery cable, and then attaching an amp gauge, can actually stop the drain right before you test for it. You must first attach your multimeter in parallel and then remove the battery cable, thus maintaining a constant circuit that will support the parasitic drain.
Yes, I can hear you now: "Thank you Pat, you're a genius."  |
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