Avoiding alternator damage

[steffen707]

Hey guys, i've got a 96 civic with a d15z1 lean burn motor in it and i'm looking to do an alternator shut off setup for it.

I've read california98civic's thread and how to on a 98 civic and he said you need to disconnect 2 wires to stop the field from being energized.

I've read that while driving, once the field is energized even if you disconnect that power wire it will remain energized and keep charging. Also I heard from brucepick that he disconnected his 4wire connector from the alternator completely and after a few minutes he was still reading 14v.

I've got a few questions. First, Stinger makes a large 80amp capable battery isolator "relay", I could use this to disconnect the alternator from the battery on the fly, but if the alternator is charging the battery and you just disconnect that connection, will that harm the alternator?

Second question is if anybody knows how the ecu tells the alternator to stop charging on these civics? There is one wire that goes to the ignition, one that goes to the charging light indicator on the dash, 2 that go to the ecu and one that goes to the battery directly.

Since we know the ecu during certain conditions will switch the alternator off, it seems to me it would be easier to just mimic this behavior. But i've read through the manual and I can not figure out if the ecu provides positive, ground, or resistance to the alternator to control its charging.

[steffen707]

Here are some good links about this.
http://sacrvators.com/ND%20alternator%20diagrams.pdf
HowStuffWorks "How Alternators Work"

From the howstuffworks website it looks like the S or F wire are the ones needing to be manipulated.

S terminal - Senses battery voltage
IG terminal - Ignition switch that turns the voltage regulator on
L terminal - Closes the circuit to the warning lamp
B terminal - Main alternator output terminal (connected to the battery)
F terminal - Full-field bypass for regulator

If L just closes the circuit to the warning lamp when something is wrong, that shouldn't do anything for us, also it looks like once IG sends voltage to the regulator its on, until you shut the car off (probably fine for you PG with car off guys, but I want an easier method). As I said before if you disconnect B on the fly that would certainly stop it charging the battery, but does it hurt the alternator, and will the alternator still be providing resistance to the engine but that electricity just isn't going anywhere?

[steffen707]

I think I might have found all the info I need from this site, Timely Topics -- Your Vigor's Charging System

It says the C wire is from the ecu and is the alternator charging control wire. Whereas the FR is the alternator charging rate and is an input TO the ECU.

It also says this"The voltage regulator puts approximately 8.5V (reference voltage) on the control wire, labeled "C" (WHT/GRN). When the ECU drops this signal to ground, the alternator will stop charging. If this wire is shorted to ground, the alternator will never charge."

Which makes a lot more sense to do if this works. 1 wire to switch and that's it. I hope the acuravigorclub is right, with the lengthy explanation I'd be willing to bet they are.

[WD40]

I look forward to your results .. I have been trying to get the answer for a while now.
Thanks for being the guinea pig lol

[steffen707]

What's the worst that can happen? I fry my perfectly good alternator.

[WD40]

I doubt that .. from what I have read this is the correct way to reduce the alt from full power out to 12.5 volts, which from what I can tell would be off assuming the battery is adequately charged to begin with. My only question is whether the wire needs to be severed and looped to the switch and back to the other end, or severed and looped to the switch that is grounded and back to the other end, or simply spliced into the wire then the switch which is grounded. (oh my I think i got dizzy from that lol)

[steffen707]

Originally Posted by WD40

I doubt that .. from what I have read this is the correct way to reduce the alt from full power out to 12.5 volts, which from what I can tell would be off assuming the battery is adequately charged to begin with. My only question is whether the wire needs to be severed and looped to the switch and back to the other end, or severed and looped to the switch that is grounded and back to the other end, or simply spliced into the wire then the switch which is grounded. (oh my I think i got dizzy from that lol)

The wire coming from the alternator needs to be cut, connected to one end of a switch, and the other end of that switch goes to ground. The wire that's coming out of the ecu would just be left "dangling".

OR, what i'm going to try.

Connect the wire coming from the alternator to a SPDT switch (see Switch - Wikipedia, the free encyclopedia) and then one of the outputs of that switch go to the splice wire that goes to the ecu, and the other output goes to ground.

This way you can have it operate as normal, or be grounded and OFF when you like.

I'm really interested to try this so I should have some results for you tomorrow, its an easy splice of a wire near the ecu and a short ground wire to the switch. HOPEFULLY!

In addition to this I would like to also try connecting one end of that switch to another micro switch that is activated by the gas pedal whenever the throttle is closed.

If this micro switch was another SPDT switch, I would set the switch's normally closed side to ground, and the other side which is activated when the throttle is closed and pushing on the micro switch, to go back to the ecu pin.

In this configuration, your dash switch would then either be normal mode, or grounded if the gas pedal is pressed or normal when the gas pedal is not pressed. Most people won't care to do this extra work, and some will say you don't want to be charging at idle because the engine is more efficient when you're accelerating, but I'm thinking that it might provide a bit of "braking force" for those in gear coast downs that I do ( I don't have an injector kill switch and don't do engine off glides either).

I'll probably find out that it doesn't do that much charging in these few times that you're coasting or idling, and might just take the micro switch out of the equation alltogether, but i'm a tinkerer.

[Tesla]

Tinker away, very interested here.
I recently had charging system failure & flat battery.
In the lead up 4 or 5 warning lights on dash were flickering under certain driving conditions.
Thought battery was gone initially, but did more checking and was not getting charge.
Jiggled wires on plug thinking loose connection maybe, all fixed, no more flickering, but 2 days later flat battery.
Turns out the sensor wire was broken and occasionally making contact, ie flickering, then finally seperated completely with my intervention, soldered wire back up and all good now.
Point to story, I had sensor wire making and breaking contact under all sorts of conditions for about a week and no fault codes or damage to alternator.
Have been thinking about doing something along these lines, but really want to do it in conjunction with a solar supply, so daytime use solar and only use alternator at nights, just need to look at appropriate sizing for solar.

[California98Civic]

Originally Posted by steffen707

I think I might have found all the info I need from this site, Timely Topics -- Your Vigor's Charging System

It says the C wire is from the ecu and is the alternator charging control wire. Whereas the FR is the alternator charging rate and is an input TO the ECU.

It also says this"The voltage regulator puts approximately 8.5V (reference voltage) on the control wire, labeled "C" (WHT/GRN). When the ECU drops this signal to ground, the alternator will stop charging. If this wire is shorted to ground, the alternator will never charge."

Which makes a lot more sense to do if this works. 1 wire to switch and that's it. I hope the acuravigorclub is right, with the lengthy explanation I'd be willing to bet they are.

The wiring diagram looks like the one for my 98 Civic DX, though maybe I'm missing a difference in details. This is an interesting idea you propose. Try it and please report back. I'll tell you that I did a process of elimination, one wire at a time. None, on its own, disabled the alternator. I then tested two at a time. When I found the combination I wrote about in the post you cite (link), I disconnected the charging light wire and then installed a switch for the other. Also, busypaws found similar results (link). If you find a better method, I'm interested.

Good luck.

james

[brucepick]

Originally Posted by steffen707

...I've read that while driving, once the field is energized even if you disconnect that power wire it will remain energized and keep charging. Also I heard from brucepick that he disconnected his 4wire connector from the alternator completely and after a few minutes he was still reading 14v.

I've got a few questions. First, Stinger makes a large 80amp capable battery isolator "relay", I could use this to disconnect the alternator from the battery on the fly, but if the alternator is charging the battery and you just disconnect that connection, will that harm the alternator?

Second question is if anybody knows how the ecu tells the alternator to stop charging on these civics?...

The diagram in the "...Your Vigor's..." link seems to match our Civics. Four "control" wires going to one connector plus one heavy power lead to starter + battery. None of the four small wires is a ground; that is via chasis/mounting bracket, as the Vigor diagram indicates. Our system is five wires total, and none of them is a ground. The four wire (total) setup in the "ND alternatordiagrams.pdf" link doesn't match what I see on our Civics, sorry.

After disconnecting my Civic's 4-wire connector, the system first showed approx 12.5 volts and dropping, but after a minute or two it came up to ~14V and stayed there. I've read that the 12V supply to the field coils (this is pretty standard alternator circuitry nowadays) activates them immediately rather than eventually, and that seems to be the case for our cars. California98Civic's approach was different; he severed one wire (with a dash switch I believe??) and left one other disconnected permanently, and got a way to disable and re-enable the alt on the fly. Slick.

I considered using a high-current-capacity relay to disconnect the alt power cable but decided against it. Nearly all relays require some amount of constant voltage to hold the switch contact closed (or open, depending on the relay design). [The exception is the uncommon type that works like an old fashioned ball point pen - pulse it once and it's on, pulse it again and it's off, ad infinitum.] In other words, aside from that uncommon type, you'll need steady battery power to keep that switch either on or off. Not my idea of conserving battery power. In my case I activate (and deactivate) the alternator rarely enough that I'm willing to go under the hood to change the switch over, and to manually connect or unplug the 4-wire connector at the alt at the same time.

That said, I'm quite curious to find out the results of trial-by-error experimentation by the folks in this thread. If it's feasible to disable the alt by manipulating some of the four smaller wires, that would be preferable to switching the heavy cable on/off manually, and manipulating the small wire connector at the same time.