On Thursday, April 28, 2016 at 7:00:30 AM UTC-5, Steve W. wrote:
> Michael wrote:
> > On Tuesday, April 26, 2016 at 4:41:10 PM UTC-5, Steve W. wrote:
> >> Michael wrote:
> >>> Or something else?
> >>>
> >>> 2003 F150 8 cyl. 5.4 L
> >>>
> >>> Driving home, the red battery ion appeared in the dash. I didn't
> >>> really notice any problems with how it drove and I made it home
> >>> ok.
> >>>
> >>> Driving back (20 minutes), I really didn't notice anything but
> >>> the ABS and red battery icon appeared.
> >>>
> >>> Driving home (20 minutes), the radio was intermittent. The radio
> >>> went off altogether. The truck began "missing" or running poorly.
> >>> I made it home, parked, turned off the engine, tried to turn it
> >>> over, and it made the dreaded clicking sound.
> >>>
> >>> Any help appreciated!
> >>>
> >>> Mike
> >> Easy to test. Get a cheap voltmeter. (even the free HF units will
> >> work for this) Hook the meter up to the battery posts with it set
> >> to DC voltage and read the voltage. Jump start or charge the
> >> battery till the truck will start.
> >>
> >> With the engine running you should see a voltage at the battery
> >> posts rise to close to 14-15 volts if the alternator is working. If
> >> the voltage doesn't rise the alternator MAY be bad.
> >>
> >> Check fuse number 11 (20 amp) in the junction box under the hood.
> >> If it blows or corrodes the alternator will stop working.
> >>
> >> Also check the battery cables, the connections on the starter relay
> >> and the connections on the alternator. Wiggle them around while
> >> watching the meter. If the wires corrode internally they could
> >> cause this as well.
> >>
> >>
> >> -- Steve W.
> >
> > Hi Steve,
> >
> > Thanks for your help! I jumped the truck and checked the voltage. It
> > started out at 14 and then slowly leaked down to nothing. I then
> > switched the 11 fuse with another 20 amp fuse and tried again, but I
> > got the same result. Wiggled the wires to no effect. It sounds like
> > the alternator.
> >
> > Mike
>
> If you want to be sure, remove the battery that's in it and connect up
> one that is charged. (you can do that with jumper cables if needed) Then
> start it and check the voltage at the battery.
> I'm suspicious of the initial 14 volt reading dropping to zero. That
> sounds more like a bad battery.
> Or it may be that you have both a bad alternator and as a result a bad
> battery. (A shorted diode in the alternator could do that)
>
> Or just pull the alternator and take it in, many parts stores will test
> them free.
>
> --
> Steve W.

Here's a question. My other car is a Toyota Highlander. If I bypass the battery on my truck and try to start it with cables from the post to the battery of the Highlander to check the voltage, will this harm anything? I understand it might not have enough power to crank my truck. I just don't want to mess anything up.

Thanks,

Mike