Quote:
Originally Posted by Randy
I modified my car to not charge via a switch. All the 5th generation Civics have an extra wire on the alternator, which if you ground will reduce the voltage to 12v from 14v. It runs from the ECU to the alternator, which has an internal regulator. The ECU drives it with an open-collector circuit (at least on mine), so grounding it out with a switch doesn't hurt anything.
Does it help the MPG? I have no idea. It dims the lights, and reduces the load due to the lower voltage. It won't kill the battery because it's still above the discharged voltage.
If this wire wasn't there, shutting off the alternator wouldn't be so easy. Alternators self-excite as long as the regulator is in the circuit. Cutting off the field or output via a relay will cause spikes, possibly damaging the regulator. The best cure is a new regulator... a switching regulator would be more efficient than the standard linear type anyway. The other way to go is to add a clamping circuit to absorb the spike. This could be as simple as a diode, but you'd need to test it.
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I just saw this thread (I'm new), which years are you refer as 5th generation?
I have Civic 2004, I do know that Honda control the alternator load throw measuring the current consumed by all the electrical loads (its even called ELD and it located underneath the Engine fuse box).
As I understand Honda do shut-off/on the alternator based on current consuming and of course ECU control.
Never tested it to see when its working on not, but my guess thats Honda know how to design cars
Thanks
Nir