Voltage Spikes/Drops after EJ Swap

[hellosubaru]

I did an EA to EJ swap a few months ago, and it runs awesome for the most part. The only issue that I've noticed so far, is that my voltmeter jumps around, anywhere between 11-14.5 volts while driving. Both the stock voltmeter and my after market voltmeter does this. It seems like if I accelerate quickly (like get on the freeway) it's even worse (fluctuates really fast).

 

The battery is never dead, but I notice when I turn the key to on, more often than not, I have 11 volts or less. Also, my radio seems to lose power when the voltage fluctuates towards the lower side. I'm not sure if this is all related, but I thought I'd list everything.

 

The way I wired the alt: fat white goes to battery, yellow goes to switched +12v, black is voltmeter.

 

Any ideas what's going on, or know where to start troubleshooting?

 

Thanks,

-Jason

[Numbchux]

History on the engine? Do you know you have a good alternator? What model/year did it all come out of, as the wiring of the alternator changed many times over the length of the EJ production.

 

 

need more background info

[hellosubaru]

History on the engine? Do you know you have a good alternator? What model/year did it all come out of, as the wiring of the alternator changed many times over the length of the EJ production.

 

 

need more background info

 

Engine / harness is out of a '93 legacy wagon.

 

The engine was one of those "70k mi" ones from a wrecker, but I rebuilt it. I have two alternators, and the symptoms are the same with both of them. I had them tested as well at the auto electric shop, and they tested good. Let me know if you need more info.

 

Thanks,

-Jason

[Gloyale]

What year/model body is the swap in.

 

From what you say, the alt wiring seems right.

 

you say:

 

"fat white goes to battery, yellow goes to switched +12v, black is voltmeter."

 

White should go thorough a fusible link back to the battery. I usually just hook the to the original EA fat, white, alternator wire.

 

The Yellow wire (assuming you mean from the EJ alt wiring) should be hooked to switched 12v. This should be the same 12v source that powers the EJ harness 12v switched. (goes into diode, becomes the Lg wire that triggers main relay)

 

The "black" wire, (It should be Black/white stripe actually) should be hooked to the "Charge" light. ....... Now in an EA81 car, this would indeed be in the Voltmeter assembly, but it isn't actually the same circuit. In an EA82 car the light is located totally seperately in the lower dash.

 

IN either case, the best place to connect the Black/white wire to is the original EA charge light wire, which should be a red/white wire in EA alt harness.

 

 

**note** If the swap is into an '81 or earlier body, you must unplug the original external VR. When you do, you're EJ harness wiring will connect there at the VR, rather than at the EA alt wiring pigtail.

[hellosubaru]

Sorry I let this go guys, I got really busy with work. I'll try to give you all the info this time. I'm going to recap a lot, but also provide new / hopefully helpful info:

 

Body of the car is an '86 DL sedan w/ d/r 5spd.

EJ22-t and harness is from a '93 legacy wagon.

 

The alt on the car currently has been tested good by a local battery/alt/starter shop.

 

Voltage between batt to block, block to body, body to batt are 0.00V.

 

Alt wiring:

 

The three wires from the EJ alt pigtail are fat white, yellow, and black/white.

 

1. The fat white goes into the stock EA fusible link box. There are three fusible links in here, but I'm not sure where they all go. On one side of all three fusible links is the battery. On the other side of the fusible links are three wires, A) Fat white from alt, black/white, I don't know where it goes, C) white/black, I don't know where it goes. I can attach a pic of the fusible link box if needed, but like I said, it's the stock fusible link box in the engine bay, so I'm sure you've seen it before.

 

2. Yellow wire from the alt goes to switched +12v.

 

3. Black/white wire goes to an after market voltmeter.

 

Symptoms: Voltmeter jumps around, anywhere between 11-14.5 volts while driving. Both the stock voltmeter and my after market voltmeter does this. It seems like if I accelerate quickly (like get on the freeway) it's even worse (fluctuates really fast).

 

The battery is never dead, but I notice when I turn the key to on, more often than not, I have 11 volts or less. Also, my radio seems to lose power when the voltage fluctuates towards the lower side. I'm not sure if this is all related, but I thought I'd list everything. When the car is off, the battery reads 11.6-11.7 volts. This is a brand new Optima red top battery.

 

Also, I can hear my fuel pump slow down when the volts drop.

 

Thanks again all,

-Jason

[Gloyale]

3. Black/white wire goes to an after market voltmeter.

 

 

This is the problem.

 

The B/W wire is for the Charge light. It NEEDS to go through a load, to a power source. That is why the "charge" light and fuse are on that wire.

 

 

Simply hook it to the W/R wire from the original ea body wiring.

 

 

OR.........Hook up a charge light. Run switched 12v to a bulb, connect the ground side of the bulb to the B/W alt wire. The light will illuminate when the key is on, eng. off. (grounding through alt.)

 

When the engine starts, and the alt puts out voltage, it drives the ground side high, and turns out the light.

 

You WILL burn out you're alt if you don't correct this.

 

 

Hook your voltmeter up to an Ig. switched 12v (can be the same as the yellow wire if you want)

Edited April 6, 2011 by Gloyale

[hellosubaru]

This is the problem.

 

The B/W wire is for the Charge light. It NEEDS to go through a load, to a power source. That is why the "charge" light and fuse are on that wire.

 

 

Simply hook it to the W/R wire from the original ea body wiring.

 

 

OR.........Hook up a charge light. Run switched 12v to a bulb, connect the ground side of the bulb to the B/W alt wire. The light will illuminate when the key is on, eng. off. (grounding through alt.)

 

When the engine starts, and the alt puts out voltage, it drives the ground side high, and turns out the light.

 

You WILL burn out you're alt if you don't correct this.

 

 

Hook your voltmeter up to an Ig. switched 12v (can be the same as the yellow wire if you want)

 

Thank you, I had no idea the charge light played that big of a role in the system.

 

Do you have a wiring diagram that shows how all of the alt connections are made? I want to see how and where it is wired stock.

 

Thank you,

-Jason

[hellosubaru]

This is the problem.

 

The B/W wire is for the Charge light. It NEEDS to go through a load, to a power source. That is why the "charge" light and fuse are on that wire.

 

 

Simply hook it to the W/R wire from the original ea body wiring.

 

 

OR.........Hook up a charge light. Run switched 12v to a bulb, connect the ground side of the bulb to the B/W alt wire. The light will illuminate when the key is on, eng. off. (grounding through alt.)

 

When the engine starts, and the alt puts out voltage, it drives the ground side high, and turns out the light.

 

You WILL burn out you're alt if you don't correct this.

 

 

Hook your voltmeter up to an Ig. switched 12v (can be the same as the yellow wire if you want)

 

Also, I don't know if it matters in this scenario, but the charge light is on when the car is turned to ON (but not running).

 

-Jason

[Gloyale]

Also, I don't know if it matters in this scenario, but the charge light is on when the car is turned to ON (but not running).

 

 

Whoa, that's weird. What is you're original EA charge light wire hooked to?

 

(White/red stripe wire in EA alt plug)

 

 

With that wire unhooked, the light should stay on all the time.

[hellosubaru]

Whoa, that's weird. What is you're original EA charge light wire hooked to?

 

(White/red stripe wire in EA alt plug)

 

 

With that wire unhooked, the light should stay on all the time.

 

Soo... I told you the wrong thing. I already have my charge light (w/r wire) hooked up to the b/w wire on the EJ alt. I also verified my voltmeter is hooked up to a switched +12v elsewhere. All other wiring I told you was correct. Sorry I didn't verify this before.

 

Thanks for the help Gloyale, I appreciate it.

 

-Jason

[Gloyale]

Soo... I told you the wrong thing. I already have my charge light (w/r wire) hooked up to the b/w wire on the EJ alt. I also verified my voltmeter is hooked up to a switched +12v elsewhere. All other wiring I told you was correct. Sorry I didn't verify this before.

 

Thanks for the help Gloyale, I appreciate it.

 

-Jason

 

O.K. well that's good.

 

So if that's all correct let's start over.

 

I would check the battery connections, the ground cable connection, and also the condition of the fat white wire going from Alt to Fusible link box. If it's all stiff, and the copper is dark brown, you could benifit from replacing it. It's fried and old from 25 years of 55 amp current. Now you're trying to push 70 or 80 through it.

 

My next guess.

[hellosubaru]

O.K. well that's good.

 

So if that's all correct let's start over.

 

I would check the battery connections, the ground cable connection, and also the condition of the fat white wire going from Alt to Fusible link box. If it's all stiff, and the copper is dark brown, you could benifit from replacing it. It's fried and old from 25 years of 55 amp current. Now you're trying to push 70 or 80 through it.

 

My next guess.

 

Ok, I finally got around to checking this stuff out tonight. Battery cables and connections are good. I also replaced the white wire running from the alt to the fusible link box, but I'm still having the same issues. The problem may be marginally better, but the problem is definitely still there.

 

Do you have any idea where the black/white and white/black wires run to that come out of the fusible link box? Also, do you know if the fat white wire from the alt is spliced into anything else other than the fusible link box? I'm wondering if I should just replace all of the wiring running into / out of the fusible link box.

 

I also noticed tonight, when I drive over large bumps or through potholes, the voltmeter needle jumps around a bit (lights dim too a bit). Not sure if this is related.

 

Thanks,

-Jasno

[Turbo GL-10]

Did you get this resolved?