Electrical issues causing huge power loss

[macipusy]

This is on a 93 Turbo Wagon. I recently noticed an intermittent power loss....feels exactly like the TMIC popped off, fuel pump is going out or dirty MAF. But its none of those items.

I can make this happen even more when turning on the headlights and heater....the car bogs down and dies.

I thought it was the alternator and swapped it out. It is still happening. The battery voltage is 14V and at the alternator it puts out about 9.8V. The new and old alternators put out the same voltage at idle.

I am leaning toward a corroded contact or a short somewhere, maybe a loose wire. I am guessing when I raise the electrical load (turn headlights on and/or heater) it starves the fuel pump of power and cuts out. I cannot confirm this, no wideband O2 installed yet.

Any suggestions where to start checking connections/wires?

[macipusy]

I checked the new alternator off the car at the auto parts store....14.6V

The alternator on the RSTi puts out 15.2V when running and my wife's 98 LGT puts out 17V when running. The turbo wagon at 9.8V.

I'll take some more measurements and update.

I am guessing this is the problem, but not sure where to start diagnosos.

[turbo970]

for one thing you car at idle should be at 14v i say check the connector at the alt to see if its turning the alt on.

[Nohbdy]

I don't know if this might be something and I'm probably wrong but check your fusible link in your fuse box under the hood. If I remember correctly when I was having some power problems with my car that was the problem. If I'm wrong don't be afraid to let me know just trying to help with ideas.

[macipusy]

14v or more is what I was expecting.

What would be the process of testing the connector at the alternator?

[macipusy]

I gathered some additional data. I compared some resistances between my RSTi and TW.

I took out the battery.

First I took measurements between the (+) and (-) battery termainal connections. RSTi = 2KOhms and rising, TW 1.5KOhms and rising

I took measurements from the alternator (+) to the (+) battery terminal connection. RSTi = 0.0 Ohms,
TW = 1Kohm and rising but slowly.

Could this be indicative of a short to ground?

[Legacy777]

Yes, that is more than likely the issue. Pretty much all wiring should have near 0 ohms. Replace the wiring between the alternator and battery and see if that fixes the problem.

[jefferson]

You could also have some corrosion built up on the main fuses. You might pull them and see what they look like. Take them in and out a few times to clean the contacts may help. I had to do that to a bike to get the voltage drop better.

Jeff

[macipusy]

I will inspect both items mentioned above by Josh and jafferson tomorrow night. I will report back with the findings. Thanks guys.

[macipusy]

I have located the problem....at least on the wiring diagram, but cannot locate the area of problem in the actual car. Maybe you guys can help.

There is a problem in the 2 main power wires coming off the alternator (held on with 10mm nut) and where they arrive at the main fuse box (under the hood). These are fairly large gauge wires in white insulation.

The wiring diagram (first wiring diagram in the FSM - Power Supply Routing) shows a SBF holder in line between the alternator and main fuse box. The corrosion or short has to be in there. I cannot find this SBF holder....the wires from the alternator go into the wheel well and then return to the fuse box from the wheel well. Is this SBF holder containing 2 fuses in the cabin area?

If you look at the Power Supply wiring diagram, I have checked resistance between connector F36 on the Main Fuse Box to the alternator. One of the power wires has 2 KOhms and the other 200 KOhms. So, there has to be either corrosion on the plug at the SBF holder or corrosion on the 2 fuses located in the SBF holder, or a short in the wires going there and back.

Can anyone help in locating this SBF holder with the 2 fuses (30A and 45A fuses). What is the purpose of these fuses, and why are they not in the engine bay?

[macipusy]

More findings. Looks like on the RS and WRX, the SBF holder is incorporated into the main fuse box. I was missing 10 pages from the PDF I had for the 92 Legacy....pages 102-110 missing from the electrical section.

I found another PDF with the missing pages....and it looks as if it is also incorporated into the main fuse box on the Legacy, but I did not see the 4 wire F42 plug on the back of the main fuse box last night.

[macipusy]

Figured it out. Had to replace all power wires on the alternator side of the main fuse box. The wire literally disintegrated into a green dust (copper oxide) at all splice locations. I don't know if there used to be a connector of some type there.

I also pulled all splice locations out of the fender well and into the engine bay. I used power wires from a WRX bulkhead harness I had lying around.

The car feels great. Has no more hesitation of any type and has a lot more power and smoothness throughout the power band. The alternator reads 14.1v at idle.


The SBF holder was actually the SBF for the ABS and ride height (which was the wires and fuse missing).

[alexandermf]

Good to hear!


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[Legacy777]

Yeah, the SBF is the jumper wire looking thing in the fuse box in the engine bay.

[beefwagon]

Hey i found a great video regarding finding power drains

https://www.google.com/url?sa=t&rct=j&q ... 6460,d.b2I

This may or may not help but its an easier way to do it by yourself to find a draw that you may have missed somewhere, good luck