Quote:
Originally Posted by rtstrack
I read somewhere that if you disconnect the negative while the car is running it will send a spike of electricty back through the car and fry some parts (maybe my MSD)?
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Not exactly true, if something is not grounded properly, it can affect it, but not by sending a spike of electricity. This is more of a problem on cars that use the on board computer to monitor and control everything. When the battery is pulled from the system, the computer tries to compensate throwing the voltages off, thereby the "voltage spike" that is not really a spike.
Quote:
Originally Posted by Rwillia4
Get a multimeter and test the voltage at the battery terminals. It sounds like the circuit that your gauge is on has other componets on it which is drawing down the voltage on that line. However this is not the voltage that the battery is seeing from the alternator (hopefully). To fix this problem change the power wire of the voltage gauge to a different circuit.
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Very good check to do before you pull the battery. If you are seeing good charging voltage here, but not at your gauge, verify that the reading at the gauge is the same with a multimeter. Simple thing that gets overlooked and causes needless troubleshooting. Never assume 1 instrument is correct. verify it.
A simple check to do as well is to pull a battery out of another car and swap it. If it goes away, you know you have a bad cell. A bad battery will load down a system and cause other components to fail. An example is on my Mustang the battery light started to intermittently come on, I had the 515 cold cranking amps battery tested and it was only 345. I changed it out and the light went away for about 2 weeks. It has now come back on 1 time for just a moment. When I check voltages, they are not stable. It looks like that the voltage regulator was working excessively to compensate for the additional load from the battery. This caused the voltage regulator to prematurely fail. It is not to the point of leaving me stranded, but it will go bad before too much longer. I have to verify the alternator is charging properly, but I am confident that it is.
If the charging voltage is good at the battery but not at the gauge, start troubleshooting by disconnecting items. Disconnect the stereo and start the car. If that is not it, pick another item until you find it.
Hope this helps.