Voltage through the roof on my BRAT

[dbenzmaine]

Hi All,

   It's great to be able to post here again!   I had an old EA-81 GL Hatch from the mid 90s until it finally rusted out from under me in 2007, and then i was subaru-less until the day before yesterday.  I scored a beautiful 87 BRAT without any significant rust.  I'm definitely excited about it.  It's in great shape, but i did notice an issue on my drive home yesterday.  The voltage bounces around while driving.  Particularly at highway speeds it will often peg at 18 for a few minutes at a time.  The fans blow harder, and the lights get brighter.  It will then sometimes run low at around 12, and then other times it'll be right around 14 where it should be.  I'm guessing my alternator is bad, but could it be the voltage regulator?

 

I've seen posts with people mentioning that they put a Nissan Altima alternator in their older subie.  If i need a new alternator, are there big advantages of going that route?  Just availability?  Would it be a bolt on swap, or would i need to adjust the pulleys and or belt length for fit? 

 

Once i get rims, snow tires, and the electric stuff fixed, the Oregon mountains are mine for the taking.  Looking forward to it.  Thanks in advance for any insights!

 

Dave

[DaveT]

Get a working alternator now.   Or regulator - not as familiar with that age.  If the regulator is separate, it's probably the problem.   That over voltage can kill stuff.  Maybe old EA81 won't be as sensitive, not sure how much electronics are in those.   But if nothing else, the light bulbs life will be shortened.  Not good for the battery either, and the rectifiers are probably being pushed hard enough to not last long ..

 

The altima mod is not a drop in.  Modify pulley position.  Add wiring and fuse big enough to carry the higher output current.

Edited January 11, 2017 by DaveT

[rdweninger]

First, get a multimeter and measure the volts with meter ... do not trust the dash meter.

Second, I believe the ea81's had an external voltage regulator.  

Third, maybe pull the alternator and have it bench tested at an auto parts store.

  If you go with Nissan alt, then yes, you will need to modify the pulley, belts and the wiring.   If you don't need more than 60 amps, no need to do the swap... just stay with stock.

[turbosubarubrat]

They are internally regulated. Regulator defiantly is bad. ea81 and ea82 alternators are the same so you can get a alternator off a 81-94. 

[BEECHBM69]

The alternator I removed from my 87 EA81 hatch had an internal regulator. I did the Maxima swap with very little effort. 

 

Remove the pulley from your old alternator, and grind/cut/sand the spacer to the right depth to make the pulley line back up. Not direct bolt on, but not terribly difficult either. I pulled the harness off the junker car with as much wire as I could reach, and wired that into my old plug so I could go back stock if I ever needed to. If you don't have anything drawing heavy (off road lights, big amp stereo, etc.) you shouldn't have any overloaded wire issues. 

 

I've noticed now my voltage stays fairly steady at idle, whereas before it would drop down to 12v or lower with the lights and fan on. 

 

Hope that helps add some perspective. 

 

Dan

[dbenzmaine]

Thanks all!  I'm guessing that pulling apart the alternator to try to remove a soldered on voltage regulator is probably not worth the effort when a whole new alternator doesn't cost much.  Gonna order a part tonight and see if it solves the problem.  I've been driving a rusty diesel Golf for the past ten years, and i'm looking forward to working on a salt-free and simpler vehicle!

[dbenzmaine]

Unrelated question, but another thing i noticed on initially looking the vehicle over is that the transmission oil is low.  In my old GL i used 80-90 weight gear oil from the auto parts store.  Is that cool, or should i be looking for something special to top it off with?

[DaveT]

If you use the stock wire and fusible link, the main risk is having nuisance fails of the link if some unexpected combinations of circumstances causes higher than stock draw from the alternator. 

 

Note - the fusing for the heavy alternator output wire has nothing to do with what loads you have in the car.  It has everything to do with preventing the output wire from starting a fire if it should be shorted to ground [or other higher current draw over what is safe for the wire] while the alternator is running.  Fuses are sized to protect the wiring.  Conversely, if the alternator rectifier/s failed shorted, the link prevents the battery from starting a fire by melting the main feed wire/insulation.

 

I almost burned my first car down due to an electrical fire because of less than ideal fuse placement, so I take this stuff seriously.  Not the most likely sort of failure, but for those who don't have tons of experience to decide what risks to take, better to err on the side of caution when dealing with electricity.