How to tell alternator is on its way out?
 

As above really, any thoughts? :wonder:

DECENT auto electrician will tell you in ten minutes.

Put a voltmeter across the battery terminals - you should see something like 11.5-12volts. Start the engine and you should see around 14volts as the alternator charges the battery, eventually dropping to around12.5-13volts

JohnD

Thanks John.

Right, first reading with engine off was 12.3 v
Engine on read 14.63 v
1 min later 12.87 v

She was a pig to start up last night, when I turned the key one click the LCD clock on the dash came on a little slower and so I thought it would be the battery as its gone dead before and the same thing happened.

Really confused now as this morning it started fine and in an instant. Last night I needed to apply the accelerator a little to help it out.

Does it turn over ok on the starter but cough/splutter as if firing on only one or two cylinders before eventually firing up? Mine did this on and off for years. I found a rather bizarre cure that I'll explain if your symptoms are as above.

JohnD

Spot on, it was like an old Lancaster one night first engine fire up then the rest would slowly come into play :lol1:

However like I say this morning was a different matter. To be fair it hasn't been driven all week so no idea if it's the fueling?

What your diagnostics matey?

Mine does that too mate. It starts 1st turn instantly almost all the time then every so often it takes a good few times turning over before it fires up. Almost to the point you say to yourself "This isn't going to start", then it runs lol
Mines been the same for two and a half years. Not sure what it is :wonder:

So its a common problem then, I want to sort it though as I look after it a lot and it's going to sound like I don't if this keeps occurring plus I can't imagine it's doing it any good as surely i'll just end up flooding it eventually.

Mine does it maybe once every two months so if it's more than that then maybe look at finding the cause. It could be like finding a needle in a haystack tho........:)

I've said it before and I'll probably say it again. If it is the alternator, invariably, it will be worn brushes which, on previous cars (Rover & Volvo) I have replaced simply and for a lot less than a replacement alternator.

On one occasion, I took it to a main dealer when I was told it was fcuked and a recon unit would be mega bucks so I bought a set of brushes for around a tenner - right as rain once replaced.

However, I have not looked at the Subaru alternator nor have I checked whether replacement brushes are available. I find it difficult to believe that they would not be.

This may sound a bit odd but mine would do it for a couple of weeks then it would revert to starting on the button for a few weeks!
After switching off I now wedge open the throttle with a stick from the pedal to the seat base. Basically, what I'm doing is venting the inlet side of the engine. I originally thought there might have been a weepy injector, fouling a plug while the fuel rail was still under pressure but it continued to do it even after an injector upgrade! I even replaced the battery and it made no difference. Since doing the above, it has never failed to start on the first turn of the key. Try it but don't forget to remove the stick before starting the engine!
I know the 'cure' sounds a bit weird and many will poo,poo it, but it worked for me!

JohnD

Makes sense. :thumb:

there was a pak file update for certain years imprezas that struggled to start on first turn of the key, it was something to do with the sensors picking up fuel when the pump primed so the pak file desensitised them for the initial start.
so johns method venting the system makes sense as it would dry any fuel out so the sensor wouldn't pick it up
it did work!

That sounds nuts John but worth a try, thanks mate!

I'm not doing any harm by leaving it open am I? Moisture wise?

Been doing it for about 3 years now with no problems!

JohnD