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Krakkles posted:It looks like voltage is probably monitored via the Generator Field (+) wire (first image in this post), as that's fed directly from the alternator to the PCM. I opened up the back of the PCM connectors, back probed that wire, and proceeded to dick around with stuff for about 30 minutes while it absolutely did not overcharge. It was later in the day, so assuming I'm right about temperature playing a part, that may be why. Dropping in as someone with no domain specific experience, but with a good idea still of how generators of this nature work... The "field" wires are how the PCM tells the alternator how much powaahhhh to put out. The idea is that you put a small amount of current into the field wires (current flows from "field +", through the alternator, and out into "generator driver"), and you get a lot of current out of the generator. So you wouldn't be sensing from the generator field connections, but those connections do tell you how much power the generator is being commanded to make. From your copy and paste, "This is done by cycling the ground path to control the strength of the rotor magnetic field.". This tells me that the + wire should always be connected to battery voltage, so it's not a surprise that the + is always at 15.8V. But the "generator driver" wire (not the "field +" wire) should vary between 0 and 14V -- when the PCM is asking the generator to pump out as much as it can, it will be close to 0, and when the PCM is asking the generator to do nothing, the wire should be around 14V. Presumably the PCM is sensing battery voltage through its own + and its own ground. This all kind of points to the idea of a bad PCM ground (which would explain it getting confused and commanding the alternator to full rear end in a top hat mode, but doesn't explain why it lets the battery droop so bad to begin with). When the rest of the battery bus measures at 15.8V, I'd be interested to see what that measurement looks like as close to the PCM as possible (ideally, inside the PCM if you can) -- between V+ on the PCM, and V- on the PCM.
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Mar 22, 2020 08:50
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| # ¿ May 22, 2024 06:21 |
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