Hi!

 

As I was cruising down the highway both the chargelamp, brakefluidlamp and stoplightlamp came on. I've noticed that they've been glowing when my car is ideling lately, but now they won't come off at all. I've assumed that the glowing in the lamps are caused by failing diodes in my alt. But I still read a good 13,5 volts on my meter. Even after the lamps have come on permanently.

 

Is it the alt? Or could it be anything else? I'm kind of hoping I will be able to drive home from dinner tonight.

 

All thoughts are appreciated

 

BFN

Chances are it is the diodes in the alt. Sort of a tell all sign. It will read good voltage at first but the amperage may be slipping. What model Subaru do you have?

Oh! Sorry about the lack of info. It's an 86 ea82 mpfi non turbo.

 

BFN

BF, Qman is correct the charging diodes sound like they have failed.

 

I have tested and repaired a few alternators

I post this pict simply to try and give some credit my post.

I have tested alts that will show an output of 13.8 Vdc or so but do not put out the charging amperage. This I believe is a fault within the alt, the charge diodes allowing an AC voltage to be presented.

You may want to check the fusible link closest to the rear of the strut tower (these are in a black plastic box located on the rad. over flow bottle) This link feeds the alt output to the battery and the cars electrical system, this link's spade connections tend to corrode.

Also please check that the alt belt is tight - highly unlikely but this could be a reason for low alt output.

Hope this helps

Skip wrote

I have tested alts that will show an output of 13.8 Vdc or so but do not put out the charging amperage. This I believe is a fault within the alt, the charge diodes allowing an AC voltage to be presented.

Easy way to check that. Put your multimeter to «Volt AC», connect the positive side to the alt ouput connector and the negative one to ground. If your meter register more than .5 volt AC, your diodes have gone.

Nice setup Skip.

Happy new year!

sometimes the positive wire on the alt will become frayed... causing these symptoms as well.. make sure the wires are good to go.

Thanks for all the replies

 

If I've understood all of you right the diodes are bad, and my alt will not give propriate amps. It will also give AC instead of DC? Could a 15 min trip do any major harm? My home is about 15 mins from here and I would like to have the car in a garage before I work on it because it's raining/snowing outside

 

BFN

oh you big wimp.. get out there an change your alternator..

 

from an alaskan without a garage! get on it!

All that the Haynes Tech book on fuel injection and ingnition systems says is that AC voltage bleed off when the diodes fail is small but can fool the ECU and create an engine misfire.

I'm no expert but I would'nt think this can harm anything permanently. If I was in your situation, I would'nt think twice about driving 15 minutes to the garage.

Good luck!

How about replacing a Loyale rad on the street side while it's snowing Battle_Wagon...

From an Montrealer with the world for a garage

BF, no harm will come of the electrical system but because you are not charging the battery, it's charge level will fall.

If it falls below about 8 volts the ECU will not function, resulting in no spark or fuel injection.

15 mim is not too long, please be judious of the high current drawing devises (heater fan, hi beam headlamps, wipers - I know it's raining maybe use them on intermitant if possible.)

You have been running on low charge to begin with (glowing lights mentioned) so you may be starting off with a partially charged bat.

Good luck

ok.. you see the BRAT in my USMB link..

 

I pulled engine/tranny and rear end in 2 1/2 hours in -5 below weather with only hand tools.

 

an alternator is childs play.. same with a radiator...

OK, BWM. you win.