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Normally an alt should be spitting out 14.4 volts while at idle. Mine is putting out 13.9 at idle and if you give it some throtle it does not increase. I checked at the alt and at the battery with the same result so I know the connections are clean. I notice that my idle suffers when the fan motor and lights are on etc. I didn't check the voltage with all that crap on but I'm suspecting the alt is bad. I did notice that when it sits and the rad fan kicks on and off that significantly drops the idle down.

any thoughts?

You certainly ought to be able to get more than 13.9 volts when revving a little.

Where were you grounding your probes when measuring the voltage?

The voltage that the regulator tries to regulate is between the Sense pin and the alternator body. To check that, put one end of the meter at the pin of the harness connector that has a white wire on it, and put the other end on the body of the alternator near that point. If you can't get over 14.1 volts there even when revving the engine, maybe you do need to replace the alternator.

But 13.9 isn't really that bad, especially if it's cold.

Hey Vikash,
yes thats how I checked the voltage, neg term on alt housing. Do you think a pep boys alt is good enough? or should I try to buy a subaru direct one?

I dunno... I'd say as long as it has at least several years of warranty on it any one should be fine, since they're easy to swap out. OEM remanufactured alternators list for $250; I bought mine rebuilt by Worldwide from Advance Auto Parts for $118 and it came with a lifetime replacement warranty, so if it ever goes bad I just pull into the nearest Advance/Checker/Shucks/etc, yank it out, and get a new one right away since it's a normally stocked item. This was only about 6000 miles ago, but so far this alternator's been good -- I get around 14.5 volts even at 700rpm idle. It came with a test chart showing that its peak output was closer to 90 amps than the rated 70.

Steve says he's had bad experiences with cheaply remanufactured alternators though, and I'm sure he has firsthand knowledge of what kind of alternators Pep Boys carries, so maybe he can chime in.

It honestly depends on what the regulator is set at. My HO alternator doesn't really go above 14 from what I recall.

I wouldn't really be worried about it IMO.

Mike you might want to try LG Armature on Westminster in Providence (west end near Classical high school). Way old-school auto electric place, gruff owner, sh!t all over the place, but they do rebuilds in-house all day long, and you'll get a real Subaru alternator not some China crap, with local return if something isn't right....$70 with core. Starter motors, too.

If you have access to a clamp meter (one with data storage ability if possible) try and use that to see what kind of current your alternator is putting out. I'm getting around to doing that myself if I can sneak the clamp meter from work out for a day.

I recommend Professor's suggestion. The OEM alternators in my experience are damn good (mine personally did 250k and still use the original starter). I may send mine there as I've been looking for a good rebuild place. Rebuilding it yourself from parts will cost more than double the OEM price. Pep Boys 'lifetime' warranty electrical stuff is crap. When I worked there, we used to get alternators and starters back sometimes several times in the first few weeks after replacement and it would take sometimes the third one to get the customer out of there, but even then, for how long? I'd rather trust a JY part then a new Pep Boys. I blame cocksuckers like Wallmart for the meteoric fall in quality for everything these last few years.

Steve

Hey thanks for all the input, I did however just buy a subaru rebuilt one from the dealer for $180. I installed it and it had a strong 14.7 volts at idle. It also had 14.6 at idle with the head lights on and the heater fan on 4. My idle did improve slightly. It doesn't drop down anymore when I turn the heat on like it was and it definately was driving better. I thought of buying a rebuilt one but I have been screwed in the past and I can afford to buy a subaru one so why not. Maybe its foolish but I trust the guy at the dealer and he takes care of me. I still however have a spiratic idle. I'm going to try grounding the coilpack a little better to see if that helps but something just doesn't feel right as a whole. The car seems to only pull hard when it gets way up in the boost whereas before it would pull hard around 7-8 psi. I'm not really sure where to go from here......

creel wrote:If you have access to a clamp meter (one with data storage ability if possible) try and use that to see what kind of current your alternator is putting out. I'm getting around to doing that myself if I can sneak the clamp meter from work out for a day.

I just realized that wouldn't work.

Why not, Scott? Isn't that how most on-car alternator testers work?

Did you reset the ECU, Mike?

I thought that they only worked on AC currents or alternating DC currents... Oh, I guess I should be doubly embarassed now.

Wait, I guess you're partly right -- depending on how the meter is designed it might only work for AC, since there are easier ways to detect the AC current through a wire than the DC current.

did not reset the ecu should I?

There are clamp meters that do DC, but they cost more. The ones from Fluke that are more than about $175 do DC as well.

You can get a china cheapie that does AC for $35.

Mike - It might help smooth things out again... Couldn't hurt.

The coil pack doesn't use a ground, so adding a ground strap to one of its mounting bolts won't do much.

should I ground the igniter then?

The ignitor doesn't ground through its body either. Its black wire is connected to the ECU's ignition ground and eventually to the ground point near the rear driver side intake manifold runner.

ahh ic, ok then

professor wrote:There are clamp meters that do DC, but they cost more. The ones from Fluke that are more than about $175 do DC as well.

You can get a china cheapie that does AC for $35.

The one I use does do DC so I should be good. I'll use a piece of threaded rod first to listen and see if the noise is coming from the alternator.

I checked out my alternator and when I put a steel rod against it I could hear a hell of a racket in there. I thought it was strange that my windows would move slooooly when I was sitting at a red light.