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Hi Guys,
Got an 06′ 4.6L mustang. Well after testing and using three different alternators still the car doesn’t show 14.v in the gauge with the engine running. It shows 11.7-11.8v while running. One of the wires of the alternator 3 leg wire plug (called sensor wire) was for some reason broken at the plug’s end and I replaced the plug (long story). This sensor wire is supposed to have 12v with the engine off. Now after replacing the plug I got 12v from the “Sensor” wire (good news), while originally read 0v, because the wire was broken within the insulation. Anyways I was thinking if the PCM has anything to do with the fact that the voltage doesn’t read right or simply the car has a “Check Charging System” on the display and the PCM is bad. The other two wires on the 3 wire plug are called GEN-MON and GEN-COM. The Gen-MON was supposed to give me 9v (engine off), but it doesn’t read anything (again, PCM problem?). One note to add is that I have great ground and added another 2 gauge wire from the engine block to the chassis. Also did volt drop testing on the negative side (alternator casing to neg post of battery) and positive voltage drop testing and all is good as far as voltage drop goes.
Bottom line the voltage of the car is not right, the alternator is new and excellent condition, but I still get the battery symbol on the car display with “Check Charging System” message. I’ll appreciate your help and recommendations on this issue.
Thanks much.
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I guess you know this…The vehicle Powertrain Control Module outputs a Pulse Width Modulated signal, but it still goes into a regulator in the alternator to control the field…The regulator doesn’t regulate to a set voltage…
I guess you do have some diagnostic specs? I’ve been looking for service manuals /training books on that system for specs and can’t come up with them.
If diagnosis states GEN MON should have 9V engine off…check and see what diagnosis states what to do when it doesn’t. I wish I could find my Ford info to help.
[quote=”JTF” post=102506]
I guess you do have some diagnostic specs? I’ve been looking for service manuals /training books on that system for specs and can’t come up with them.[/quote]
Ask, and ye shall receive:
http://iihs.net/fsm/?dir=0
Specifically: http://iihs.net/fsm/?dir=361&viewfile=Charging%20System.pdfThis really isn’t any pattern failure or common problem with these. This is quite oddball if the PCM is actually to blame.
I have to ask before you go re-flashing/replacing that PCM, you have checked for continuity from the battery positive to the B+ terminal on the alternator (verifying the fusible link isn’t toast), and the fuses, yes? PCM lines themselves also for continuity/corrosion? Pinpoint test B in the above link should help, if you’re not already using that for diagnosis. I’d especially verify those PCM lines first.
I’m on alternator #3 myself. First cooked the diodes, all but one was cracked. Second the voltage regulator went, likely same reason as first. And this isn’t limited to myself with these, so I’d call the alternators a common failure point overall, but not the PCM.
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