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Working too hard, worrying too much Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 16 Apr 2001 14:07:01
In Reply to: Re: Voltage drop with ACC cycling on 97 Aero, starter cranking ..., BobS, Mon, 16 Apr 2001 13:29:13 Members do not see ads below this line. - Help Keep This Site Online - Signup |
If under a major electrical load (A/C clutch, fan on, etc.), you get a few hundred millivolts of drop, that's really no big deal. In order to make the car's power system so 'stiff' that it didn't drop any voltage between no load and full load, the car would weigh another 150 pounds between 10 gauge wire everywhere and an alternator the size of an oil drum. An occasional drop down into the lower 13 volt range isn't going to do anything any harm - in fact, you could occasionally drop down below 12.5, and all that happens is that you're pulling some current out of the battery to help things along. As long as the electrical system only goes there on transients, and doesn't operate continuously with the battery in discharge, it's no big deal.
The EDU voltage indication is OK for checking the relative health of the electrical system, but isn't a good troubleshooting tool. It's not a precision instrument, and you really don't know where the voltages and ground is picked up. It could be at the long end of a wire with a large load. The EDU also has a slow sample rate, and from observation, also appears to have a heavily damped response. The only true tool is a high speed meter right at the battery.
My big complaint with the EDU display is that with it there, folks start to fixate on every tenth of a volt. It serves a use to indicate relative battery health at startup. If it goes over 14 and change when driving, or below 12.5 and stays there, you've got a problem. But I think it's not a good way to try and discern more than general trends.
, Sun, 15 Apr 2001 23:53:23, Tue, 17 Apr 2001 16:47:58, Mon, 16 Apr 2001 13:03:08, Mon, 16 Apr 2001 14:07:01 <-- Viewing This Message
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