Charging Issue

hows the actual battery ground? id go over every ground wire i could if i were you

 

I think the battery ground is good. I've tested the voltages in other locations and they're not too far off from what the battery has.

 

How far off? They should be near perfect when it's acting up or anytime.

If you put a meter lead on the the positive battery terminal and keep it there, you should measure the same voltage within a 10th or two, when you put the other meter lead to the other battery terminal, the connection to it, the engine block, the body, etc. Same if you put one meter lead on the battery negative terminal and measure to the battery positive terminal, it's connector, the alternator output, etc. These should all be stable when things are acting up or anytime, if not you've found a problem.

Another way to test is to measure the voltage across the connections on the positive side and then again on the negative side. In other words, you should measure zero volts from the battery positive post to the terminal connected to it, the other side of that wire, the fuse, the alternator, etc. Same on the negative side, zero volts from the negative terminal to the chassis or the engine block, etc.

Hard to explain, but there should be no voltage drop across a good connection with no resistance.

 

I'd check voltage drop, battery + to alt + and battery - to alt housing. Not sure if our alternators have a temperature sensor but that could play a part as well.]

Current must flow for a VD test to read anything.

Also check your field voltage.

 

I guess I should have said check the voltage directly at the Alt first. Silly me.

 

Okay, I'll do some more tests today.
Thanks!

 

Okay, so I did find a broken wire. I wish I knew how it happened, but the wire from the alternator to the fuse box behind the battery, was broken right where it connects to the fuse box. All better now.
Thanks guys!!

 

Possibly the wire was fairly corroded and when you pressure washed the engine bay the "pressure" severed the connection. Either way as long as you fixed the wire and it's all better who cares. Good hunting.

 

Sounds like either a temp sensor wire or wire or field voltage, either of which if they were varying in current/continuity could do what you described.

 

You problem is consistent with an intermittent connection between your alternator and the battery. The easiest way to find the problem is to start with the source at the output of the alternator with the engine idling and measure the voltage. If above 13 VDC, then proceed to the terminal on the end of the connecting wire to the alternator. If above 13 VDC, then measure the positive battery post. The battery light indicates a miss-match in voltage between the battery and the output of the alternator. Many things can account for the light to be on, such as a broken or loose alternator belt, post/clamp corrosion, loose or broken cables, or faulty battery or alternator/voltage regulator. Wiggling wire or connectors while measuring the voltage can often assist locating the problem.