400 Charging System Not Functioning - What else could the problem be?
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From: Oregon
WIth the DMM set between battery neg and the ground strap, , it's reading around a 3A drain, when I unhook the harness with the red/green wire, drops to 0A.
Last edited by ihateminimumwage; Apr 30, 2007 at 09:18 PM.
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You either have an ignition switch problem, or possibly you may have hooked a stereo or other component up, and got the memory wires and the key power wires mixed together, were the battery is now feeding backwards through the power wires.
I think what I would do first is disconnect the plug on the ignition switch. If the problem goes away, we can assume the ignition switch is not adjusted or faulty. If your key is on the column, look for the ignition switch on top of the column, under the dash.
You could also try pulling fuses to see if you can kill the voltage problem, just to try to narrow down where it's coming from.
I think what I would do first is disconnect the plug on the ignition switch. If the problem goes away, we can assume the ignition switch is not adjusted or faulty. If your key is on the column, look for the ignition switch on top of the column, under the dash.
You could also try pulling fuses to see if you can kill the voltage problem, just to try to narrow down where it's coming from.
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From: Oregon
Thanks so much for all of you folks help so far...
No key in the column. I'll go unplug it right now and see what happens...
Stereo is unhooked, and fuses didn't do anything before, but I'll check again...
No key in the column. I'll go unplug it right now and see what happens...
Stereo is unhooked, and fuses didn't do anything before, but I'll check again...
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From: Oregon
Alright, scratch that. I just unhooked the switch, and there was still the drain, which didn't make sense... So I unhooked the red/green again, and the drain was still there (I guess I screwed up with the readings somewhere along the line last night?).
There's also still power at the coil, around 5.6 mV with the battery hooked up (MM neg @ batt neg, MM pos @ coil pos) and it reads the battery voltage when the ground strap isn't hooked up (MM neg @ batt neg, MM pos @ coil pos).
How frustrating... SO it's not the ignition switch (of course not, that would've been too easy...)
Sorry Dave, I didn't mean to lead this in the wrong direction.
There's also still power at the coil, around 5.6 mV with the battery hooked up (MM neg @ batt neg, MM pos @ coil pos) and it reads the battery voltage when the ground strap isn't hooked up (MM neg @ batt neg, MM pos @ coil pos).
How frustrating... SO it's not the ignition switch (of course not, that would've been too easy...)
Sorry Dave, I didn't mean to lead this in the wrong direction.
Last edited by ihateminimumwage; May 1, 2007 at 01:45 PM.
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With the battery connected, and the MM pos on the coil pos, and the neg on the engine block (I tried a few different places) it was registering around 255 mV on the exhaust manifold, but it was fluctuating up and down a lot. On valve cover bolts it was saying -100 mV, but was also fluctuating. I didn't know where to put the neg exactly, as the motor got a full paint job with the rebuild, and it seemed to have different readings wherever I put the meter...
It was 5.6 mV when the batter was hooked up and the meter was run between bat neg & coil pos.
It was 5.6 mV when the batter was hooked up and the meter was run between bat neg & coil pos.
Last edited by ihateminimumwage; May 1, 2007 at 02:39 PM.
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Okay, I just ran out to my truck because I'd left the battery cables connected after the last tests...
Figured I'd check the alternator, and it's still the same with no key switch installed, power drain when F wire is hooked up, drain is gone when the F wire is pulled. Also when I pulled the F wire, any voltage going to the coil disappeared.
What part in the system could possibly cause power to the alt (which was hot to the touch because the battery had been connected) and power to the coil? These are the only two parts that seem to be getting constant power, and they are interconnected in some way.
It seems like after pulling the key switch, it might narrow things down a bit?
Sorry, I'm just stressing because I start a new job tomorrow (of course it's one where I need my truck
) so I'm trying to juggle truck repair, building a deck and prepping for the job tomorrow 
. Also hopping back on here for info in between all those...
Figured I'd check the alternator, and it's still the same with no key switch installed, power drain when F wire is hooked up, drain is gone when the F wire is pulled. Also when I pulled the F wire, any voltage going to the coil disappeared.
What part in the system could possibly cause power to the alt (which was hot to the touch because the battery had been connected) and power to the coil? These are the only two parts that seem to be getting constant power, and they are interconnected in some way.
It seems like after pulling the key switch, it might narrow things down a bit?
Sorry, I'm just stressing because I start a new job tomorrow (of course it's one where I need my truck
) so I'm trying to juggle truck repair, building a deck and prepping for the job tomorrow . Also hopping back on here for info in between all those...
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From: Oregon
Just catching back up with this thread...
The 5.6mv to the coil is "in the noise" as us electrical engineers like to say.
But the hot alternator is a definite problemo. By "no key switch installed", does that mean that you have the connector to the ignition switch disconnected?
Back to the original cause, the shorted starter cable. That may have melted insulation somewhere, somewhere bad. Look closely at that ignition switch connector. Then look closely at the whole primary/engine harness. I'll try to look at a similar schematic tonight and see if any likely source comes to mind, but as someone (Dave?) said, the field should not have voltage with the ignition switch in the off position...
The 5.6mv to the coil is "in the noise" as us electrical engineers like to say.
But the hot alternator is a definite problemo. By "no key switch installed", does that mean that you have the connector to the ignition switch disconnected?
Back to the original cause, the shorted starter cable. That may have melted insulation somewhere, somewhere bad. Look closely at that ignition switch connector. Then look closely at the whole primary/engine harness. I'll try to look at a similar schematic tonight and see if any likely source comes to mind, but as someone (Dave?) said, the field should not have voltage with the ignition switch in the off position...
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From: Delaware
I think that there is a short to an 'always hot' wire and the low(coil) side of the ignition coil ballast resistor or resistor wire. When the keyswitch is open, it provides voltage to the field through the ignition resistor. When the keyswitch is closed, the ignition ballast is bypassed.