Electrical "resistance"

sicksteve

Active Member
In my '76 455 Riv, its 10SI alternator was putting out a decent amount of voltage at idle, and the battery kept its charge. There NEVER was a short. and a totally new hi-po HEI system and wiring was done, which both worked great.

Now, the NEW optima goes dead in a few days, and there's resistance between the "+" post on the alternator and "+" post on the battery. It's like some load draining on the car's battery

People have been vandalizing all my collector's cars, in really childish ways.

any quick way to locate a possible short or continuous load?
 
nd there's resistance between the "+" post on the alternator and "+" post on the battery.

of course there's resistance. the question is, how much? less than 1 ohm would not surprise me. i would think 1-5 ohms would be getting kind of flaky. higher than that and you definitely need to clean all of your contacts and check every cable.




any quick way to locate a possible short or continuous load?

1 - a "short" would be the opposite problem from having excess resistance in the charging circuit. excess resistance would limit current before it ever got to the battery, a short would draw more current from the battery, even with the ignition turned off.
2 - disconnect your battery and with the car off check resistance across the + and - battery terminals. if you see a resistance of ... let's say less than 1,000 ohms then start pulling fuses out until you see the resistance jump towards infinity. if your DVM has a high enough range you will never see an 'out of limit' reading though. modern cars all have a constant current drain on them as they maintain radio station presets, monitor for car lock remotes, etc. older cars will have a much higher absolute resistance with the ignition off as, if you don't have a clock, there probably isn't anything left running when the car is off.
3 - this problem really sounds more like the alternator decided to quit working on you and the car is running off of the battery full time. take the alternator into an autoparts store. most of the chain stores will do a free diagnostics test on it for you. voltage across the battery with the car turned off should be ~12.5v and with the car running ~13.5v and up.
 
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