Charging system issues.

[C.Evans]

Ok here is the deal... New alternator and old alternator both charge 17.5 volts at idle to the battery. Alternator gets hot as fuck. Disconnect the red wire from the back of the alternator and it is putting out 14.2 volts to the stud that the wire hooks to. WTF is that? Hook wire back up and it puts out 17.5 and the alternator gets hot again. Bad fusible link that is in the wire running from the alternator to the starter?

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[RICH17]

Make and model? or your Ranger?

 

[RICH17]

Nvermind seens this was in 3800 section. What vehicle

 

[C.Evans]

2000 Grand Prix

 

[RICH17]

I'd almost say that there is a connection problem. Or that the power wire is being grounded from the alt to the battery. What does the fuse box and the battery terminal put out when its idling??

 

[C.Evans]

As soon as I hook the wire up to the back of the alternator there is 17.5 volts everywhere. Unhook wire from the back of the alternator and put meter on stud coming out of alternator and it puts out 14.2

 

[RICH17]

I'd say to put it back on when the whole engine bay is as cold as can be and then let it run while feeling the whole harness. Smell anything burning?

 

[C.Evans]

The plastic protective cover that goes over the positive terminal on the battery looks melted. I ran a wire straight from the alternator to the + side of the battery and it was charging fine that way. Also when it overcharges the little vehicle display on the dash above the radio that tells mpg's, what doors are open, etc. etc. shuts off. Sometimes the abs and trac lights kick on, and the blower motor as well. Where is James, is he awake?

 

[C.Evans]

It doesnt overcharge all the time, only randomly.

 

[02BlueGT]

There is a reference on the back of the alternator (small 3 wire connector) this directly affects the voltage regulator, check this harness for breaks/melted wires. The fusable link should only melt from a short to ground after the link or at the starter, the alternator can't really melt it on its own.

 

[C.Evans]

It only puts out 17.5 when the single red wire is connected, 14.2 when it is disconnected. 3 wire conector plugged in both times.

 

[02BlueGT]

It only puts out 17.5 when the single red wire is connected, 14.2 when it is disconnected. 3 wire conector plugged in both times.

3 wire is your reference, so the alternator is getting a low reference and upping the voltage to compensate. It is possible that you have a bad voltage regulator(IIRC they are internal to the alternator on our cars).

 

[C.Evans]

Old alternator and the new one act the same way. May have to dig into the wiring for the connector.

 

[C.Evans]

Any more thoughts?

 

[1quick]

did you check the wire that comes off the alt and make sure it isnt grounding someware, maybe run a new wire from the starter, that shit is pretty small anyway

 

[C.Evans]

I did. I should probably add that this all started right after I did a front brake job.... I had to beat the drivers side rotor for about 10 minutes with a sledge hammer to get it off of the hub since it was so rusted. Maybe it has something to do with the abs module and wheel bearing? Sounds stupid but I pulled a wiring diagram yesterday and parts of the charging system seem to go to the abs module.....??

 

[1quick]

un plug the abs module and see what happens, i dont have abs i took all that crap off and i rewired my whole charging system with 2ga

 

[C.Evans]

Im gonna do that tonight. Never thought about it last night since I was tired as hell.

 

[Turbocharged400sbc]

backprobe the pcm and alt and check voltage drop while running, also to rule out battery cables which love to cause issues with corrosion do the jumper cable bypass to rule out the power or ground cables if youy dont wanna voltage drop test those

are all 3 grounds at the bellhousing bolt good? the chgassis ground good?
a branched plate in the battery can really cause some odd shit when internal battery resistance drops or rises

 

[Mr_Roboto]

Is it a pink wire with a black tracer? If so that's power to the regulator. If you have 2 wires then I will hypothesize that the other wire goes back to the dash and the bulb runs in series with it to power. At least this is how the old CS-130s were wired. I ran into a problem on my van where it wasn't charging. Bought a new alternator and replaced the battery, no dice. As it turns out I unplugged the connector at the alternator and the charge light stayed on! This basically meant I had a short to ground, which meant that the alternator would always be switched "off." The fix was to shunt a bulb from the pink/black wire to the brown wire at the alternator, and disconnect the light in the dash. In your case you may have a different problem, such as an increased resistance in this path. I think that hooking a bulb up as I described and seeing if your output drops is a good call. If so it is likely there is excessive resistance some where within the light circuit.