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Car Forum / Driving, Maintenance, Tuning / Car Audio / July 2005alternator voltage Q
This might be a little OT but I know the brains for it are here, and my electronics is rusty as ****.. My wifes truck has a low running voltage, just maintaining 12v @ idle, up to ~12.7 engine reved up. My measurement of the neg battery terminal to chassis ground (ground bolt on fender) is 0.7ohms, but my measurement of the alternator casing to battery - is 8 ohms, and yes there is a ground strap from the battery to block, and battery to fender.. Should an 8 ohm resistance between the alt casing and ground be enough to cause the ~2 volt low condition? My first instinct on this is to go ahead and run 8 guage from the alt case to battery neg, but it's in a bad spot for the job and want to have some backup on the idea it will actually work... it's gonna take significant effort.. > This might be a little OT but I know the brains for it are here, and my > electronics is rusty as ****.. [quoted text clipped - 10 lines] > backup on the idea it will actually work... it's gonna take significant > effort.. The resistance between the alternator case and the battery negative should be less than the resistance of your meter's own wires. Maybe you just need to knock some rust off. The voltage should be 14 - 14.7 volts. >> This might be a little OT but I know the brains for it are here, and my >> electronics is rusty as ****.. [quoted text clipped - 16 lines] > >The voltage should be 14 - 14.7 volts. I agree with Kevin. The primary ground path for your alternator case should be from the case through the mounting brackets to the block, and then from the block through the ground strap to the negative terminal of the battery. The resistance of your meter leads shouldn't be more than 0.2 ohms, so almost all of that 8-ohm resistance is coming from a bad connection, most likely the ground strap. Remove both ends, sand the cable ends and the mounting points, apply some dielectric grease to the mounting points and cable ends, then reassemble everything tightly. With your low voltage output at idle and at speed, you might have a failing alternator or voltage regulator, but you're not going to be able to accurately troubleshoot any further until all of your connections are in order.  SignatureScott Gardner "The only time you can have too much fuel is when you're on fire." I'm having an identical problem, so I'll report back when I get it sorted out... Here's a dude that solved a similar problem, but obviously it could be a number of things... http://www.misterfixit.com/dedbatt.htm >This might be a little OT but I know the brains for it are here, and my >electronics is rusty as ****.. [quoted text clipped - 10 lines] >backup on the idea it will actually work... it's gonna take significant >effort.. |
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