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Could somebody help a friend on another forum please?


istruggle2gate11
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Could some kind soul pop over to this post to help a friend and regular off-offroader out and if can answer, please reply here, I will point Sam in this direction, I know its cross foruming, but saves membership that might not be used.

The vehicle is a jeep cherokee 2.5 diesel, about 1995 I think, its run on a budget, and is a reliant road motor as well as off roader.

Ta.

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DelcoSI.jpg

PICT0632.jpg

Assuming the photo and diagram of the alternator correlate, the two wires will be 'sense' and 'Field (D)'

In terms of identifying which is which in the loom, with the ignition on (not cranking, i.e. at the point you'd expect to see the alternator/battery warning light) grounding each of the two green wires through a test bulb (important, if not you will have a direct short) should make the dash warning light glow.

Alternatively, you could measure the resistance between the green wires and the positive terminal, in theory the higher resistance will be the 'Field (D)' wire as you'll be measuring the resistance of the bulb. In practice, stray resistances on the path between the dash and battery could make this harder to do.

Yes, the sense wire is there so the alternator knows how much to charge the battery, most alternators use 'machine sensed' regulators, there is no need for this extra wire as the alternator simply looks at the voltage at the output terminal, assuming this is also the voltage of the battery. the alternator here is battery sensed, so its actually looking straight at the battery's voltage. as this wire will draw little current (in contrast to the main battery lead, which handles a lot of current) there will be negligable voltage drop/resistance, so the measurement of the battery's voltage is accurate.

I doubt the alternator will work at all without these wires connected, as it will need exciting (the field windings need a voltage across them to generate the magentic field needed to excite the stator windings), this is provided by the current through the warning light, once its running it will self excite.

In terms of telling 'sense' and 'field (D)' apart, in theory if you could put a <14.4 voltage on 'sense' you should see the output voltage rise.

Right now, i'm struggling to come up with a definitive test, still looking at it though.

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Right now I could make some educated guesses, but I will look at the workshop manual tomorrow. My 2.8 2004 Cherokee Ltd has the same wiring, but the alternator is a Nippon Denso, that I have changed once due to the clutch pulley failing...................

I will probably reply direct to the post ;)

Edited: Both Luke and myself posted at the same time ................. I'm 100% sure that Luke is correct ............... but I will check the FSM as planned

:)

Ian

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