one, two, three, four!
Rev up your engines!
It's time for the Scotty Kilmer Channel
if your car's having strange electrical problems then stay tuned, because today
I'm going to show you how to use a simple voltmeter to find electrical
problems in your car, now realize that in your car the battery supplies both
positive power and negative ground power, and many times when weird things happen to
your car, like you step on the brakes and the parking light comes on, you have a
ground wire problem, which can often be hard to find, now even I can't see
electricity, so you need to test for it, using this voltmeter you can find bad
grounds quickly, first hook the meter up to your battery,
positive to positive, and negative to negative, and in this case we get the
battery voltage of twelve point eight six, which is normal for a good battery,
now say you want to check to see if the engine is grounded correctly, it's
easy, just take the negative test lead off the battery, and then clamp it on
something solid like this metal part of the head, and as you can see it's still
exactly twelve point eight six volts, that means that the engine is perfectly
grounded when the engine is shut off, but that's not a good test, really you want a
dynamic test to see if it works when the engine is running, now to do that we
have to retest it with the engine running to see what the voltage is with
the alternator running, which in this case is 14.26 or 14.27
it keeps moving around, then we'll take the negative terminal
off again, and hook it up to the block and see what the reading is, in this case it's
14.27 so it's good when it's running too, now if the reading had been 4/10 of
a volt or more in differential, there would be a problem with the grounding wire,
but it's the same so that grounding wire is okay,
for instance if it would have read 13.06 volts that would have meant it
was more than 1 volt less, which would mean there's a problem in the grounding
wiring, now realize that there's ground power wires everywhere in a car, like
this one on the back of the firewall here, and you want to test them with the
engine off, and with the engine on, to see if there's a problem either way, and if
you find that either one of the readings is 0.4 of a volt or more off, that means
it's a problem in that grounding wire, and you got to trace the wiring or the
connectors at the ends, to see if they're corroded or loose, because if you do have
a bad ground wire, when you use that device, it'll often try to draw power
from other devices and turn them on, so weird things could happen like you step
from the brakes and the parking lights will come on, because it'll start to turn
those devices on, when that happens you almost always have a ground system fault
somewhere, sure there's grounding wires all over the place, like in the trunk of
this Mitsubishi, you can see they run off the lights, but now that you know how to
test them with a voltage meter, it's very easy to find out if the grounds aren't
working correctly, and I know some of you are going to ask, why do I have to test
with the car off and the car on, well that's because a weak ground wire might
work ok with the car turned off, but when all the power is running through it, if
it's got a bad connection or a short and end on it, it won't take extra power and
you'll see that by a bigger voltage drop, knowing there's a problem, so just like
any other machine, it's much better testing them when they're working
instead of when they're just sitting there doing nothing, and the act of
dynamic test is much better than static test,
after all you want everything to work on a car while you're driving it, you really
don't care what it's doing it's just sitting there resting, so now you know
how to do a voltage drop test on grounding systems, just remember if you
have more than point four of a volt difference, you got a problem in the
grounding system, and remember if you've got any questions just visit the Scotty
Kilmer channel and I'll answer them as soon as I'm done drinking some of this
moonshine!