Big voltage fluctuation.

[Stoner51]

So. I need some help.
For the past month I have had the dmm iny car monitoring the voltage. It will consistently go from 14.4 down to 12.4. Usually when I let off on the gas. Not all the time but that is the trigger. Sometimes it goes back up usually it doesn't . Once I use a fairly heavy acc (ac rear defrost)the voltage comes back up.
I have always had to replace the batt in this car every two years not matter what batt I put in.

Well Monday it 35 outside car wouldn't start. Took battery to autozone. It's dead. The batt was a 24 series, not sure why they gave me that one, anyway I replaced it with 34 series, more cca.
So after the batt died I took my old alt to advance. They tested it. Said it was fine. So I put it back on. Took the high output one up to be tested it failed.

So after that I thought that must be the problem. Nope it is still there.
Connections are good and tight grease on them. Belt is tight. Batt is new and alt tested out good.

What am I missing? Is this normal? Ie if the car doesn't need power does it regulate it Down to 12v. The odd thing is when driving the voltage goes down to 12.3. With the car off the voltage is 12.6.

This is baffling me.
As always thanks

Steve

[wildBill83]

Sounds like you need a new alternator and battery...

Or rebuild the alt you have, replace the brushes and diode.

Either way, depending on the age of the batter and the number of full discharges you may want to strongly consider a new battery. If the battery is near new and only discharged once it will reduce CCA but should not kill a new/rebuilt alternator.

It is common for a bad alternator to test ok...

[Stoner51]

Batt is new. I got it Mon. I'm not convinced I have two bad alt. Thats too much for me to believe.

There has to be some other part. Do you know anything about ELD?

FYI: car 91lx MT, big 3 done with knuconceptz 4ga wire. 4ga alt wire to the fuse box, plus the stock wire.

steve

Please don't think I don't appreciate the help. I just find it hard to believe I have two bad alts. I would like to make absolutely sure before I go buy another one and it not fix my problem.
I have no need for 3 alts

[wildBill83]

Try bypassing the ELD to elimante it as a problem. Also recheck your grounds. Also test the alternator under load at the alt and at the fush box.

[Stoner51]

How do I bypass the ELD?
Under load the alt puts out volts at 14.4. It is off load that it drops to 12.3-12.4

I checked the grounds about a week ago. they looked good.

steve

[wildBill83]

How do I bypass the ELD?
Under load the alt puts out volts at 14.4. It is off load that it drops to 12.3-12.4

I checked the grounds about a week ago. they looked good.

steve

That sounds like your ELD is working correctly. I would check the charging circuit for open wires.

What is the condition of the connector that plugs into the back of the alt?

TEST ELD (source = Haynes manual):
1)You need a multimeter! Disconnect the electrical connector from the ELD system and measure voltage between the black/yellow(+) and the black(-) wire (2 outside terminals) with the ignition key on (engine not running). There should be battery voltage(picture shows 12.11 volts). If no voltage is present, check the wiring harness back to both fuse boxes.
2)Measure voltage with the ignition key on (engine not running) between the green/red(+) terminal and the black(-) terminal. There should be 4.5-5 volts (picture shows 4.59 volts). If no voltage is present, check the ELD circuit between the engine and alternator.
3)Reconnect the 3 pin connector to the ELD system. With the ignition key on (engine not running) and the headlights on, measure the voltage on the green/red(+) terminal (middle terminal). There should be approximately be 2 volts.
4)If the tests are not correct, replace the ELD unit. This requires changing the entire main fuse box. The ELD is not available separately

BYPASS ELD (source = H-T and Sounddomain):
http://honda-tech.com/showthread.php?t=2873474
http://forum.sounddomain.com/ubbthre...page/0/fpart/2

[Stoner51]

Yes I just did that. All my numbers look to be in order.
My dmm diret at batt was 12.39, at the ELD it was 12.21
GRN/RED to ground was 4.63

Plugged in GRN/RED to ground it is 3.56. My honda manual says 2v.
It says if voltage is not specifed replace the relay box (ELD unit is not avail seperate)


So do you think the 3.56 volts is too high and this is causing my problem?

thanks

steve

Oh it says if the voltage is above the ELD is ok

[wildBill83]

You can put a resistor on it to drop it closer to 2V if you want to test it, but I would assume the ELD is in order. You aren't seeing 0V, 5V, or 12V there. 5V or 12V would indicate a short and 0V would indicate an open line.

Continuity test the charging circuit from the alternator to the battery.

If everything checks out, try replacing the brushes in the alternator.

[Stoner51]

By testing the charging circuit I assume you mean power in to the fuse box and a ground?

I looked at the brushes yesterday and they looked good. Then I took it up to advance and they tested it. I had planned on buying new brushes but they were good.

steve

[wildBill83]

I'm away from my manual, but basically continuity test from the Alt to the battery, then continuity test the battery (-) negative terminal to the engine block and the ground in the alt plug.

Do you still have the exhaust heat sheild in place?

[Stoner51]

yes to the heat shield.

How do I test for continuity?

steve

[wildBill83]

Do you have a multimeter? most have a closed circuit or continuity setting, if not use the Ohm setting.

http://www.ehow.com/how_4537480_test...ontinuity.html

When I said test to the battery above, be sure you remove the battery entirely and test the wire that hooks up to the battery. You don't want the battery in the circuit you are testing.

EDIT:
If your alternator throws out 14v and your battery can charge and hold a charge and the EDL is good then the problem lies in a bad connection somewhere.

[Stoner51]

Thanks. I will have to do that later.

steve

After doing some google searching. I have almost come to the conclusion that this is the function of the ELD to drop the load when its not needed.

My problem is at idle when the the voltage is low I can tell a difference in the smoothness for lack of better word.

[wildBill83]

Then bypass the ELD, it will affect your gas mileage negatively.

Yes the ELD switches from load and it is functioning correctly if it switches.

[Stoner51]

So I was about to order the relay and then I read it will affect my gas mileage.

May I ask how?

Steve