A simple way to do this, without bothering any of the existing wiring, would be to run a small *fused* wire from the output of the alternator to the charge relay. You may need a diode... I don't think so as long as you attach to the existing alternator side of the charge relay.
And here's how I handled that:
There is a 3rd wire on the Isuzu plug...white/green on some, brown/green on mine I believe, and I just put a 15A fuse on it and spliced it into the 'Zu yellow/white and Ford green/red.
That's it!
I actually did this about a month ago and have put approx. 800 miles on it since then. That's how slow I am at scanning photos. <img src="/forums/images/graemlins/smile.gif" alt="" />
<img src="/forums/images/graemlins/cheers.gif" alt="" />
Phil
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This doesn't sound like the best idea. While this does work, it kinda doesn't either. The output from the alternator goes to batt positive. If you splice the charge relay into that, you're energizing it *all* the time. Even with the truck off. The charge relay no longer comes on just when the engine is running.
This means:
The charge light won't come on (ever).
In case of an accident, a dead engine won't stop the fuel pump.
The battery will go dead if parked long enough (okay, a long time maybe).
And, Phil's wiring must be slightly different than mhy '94 Amigo. On mine, doing this would result in things like the fuel pump running *all* the time, air regulator powered all the time and everything else the charge relay kicks off being powered all the time. These obviously can't be happening for him so you should really study the wiring diagrams for your truck to see what will happen. You could even test it now with your current alternator in place and put in a jumper from the alt output like he did.
To do it like this you should use a really BIG diode. Cut the main power line from alt to battery and install the diode so juice goes from alt to battery, but can't go the other way. When you splice in the wire for the charge relay, do it between the diode and alternator so it can't get power from the battery, only from the alternator. This is is a pretty good way to go, but you need diodes rated for at least the max amperage of your alt and this can be big, expensive and/or hard to come by. Maybe you could scavenge the rectivier diodes from another alt...???
Secondly, does your alt use a separate battery sense wire? That will need to be run to battery to sense battery voltage. A lot of alternators (most GM and our Isuzu one as well) have a separate pin for battery sense, but it just taps into the the alt output to the battery at the wiring connector for the alternator. With the diode in place, it'll no longer work. You'll need to re-route this so it connects between the battery and diode so it can sense battery voltage. Some alts have this connection internal. If that's the case, you're screwed or will have to do surgery on your alt.
--Dan
