having some issues with a 99 5.2, i have a voltage readout that i plug into the cig lighter i get 13.8 at idle then i turn everything on wipers, headlights, radio, ect and the voltage drops to 13.1 or so. also new bat installed. so is the alt shot or on its way out. i would assume this is the original.

 

i would say some voltage drop is normal, but your alternator isnt putting out enough voltage to begin with, it should be around 14-14.4 with the engine running, i would change the alternator if i were you and i was getting this behaviour at the battery posts.


also i only trust the reading at the battery myself, i would simply put a voltmeter across the terminals and see what it says because there will be some voltage drop through the system due to resistance in the wires, you want to minimize this error by checking at the battery.


i have to ask what makes you think the alternator is bad besides the voltage drop?

 

+1 Why?

You put a load on the system, of course there is going to be a drop.

However I am intrigued at your situation because I always thought that the Cig lighter was regulated to 12 volts, but with your statement I would like to verify that it is not regulated as it would make more sense and I have never tested it out?????

Has anyone ever measured the voltage at it? Sounds like a fun!