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`95 Legacy L with 'whine' & weird smell.

Hello all,

My mom called me from work earlier today regarding an issue that started happening with her legacy L wagon. On her way to work she first heard what she described as a high pitch/whine noise coming from the engine compartment. While she was at work, I took it to the dealership and on my way there, I could hear a a similiar noise. It reminded me of what happens when a belt is too tight around a pully and the noise it makes when the belt is rubbing hard against a pully.

The second issue was that there was a "heavy chemical smell" coming from the engine compartment blowing back in the window. I too smelled this and the closest description I can give is that it is a mixture of a burnt belt/hose smell mixed with that of a chemical nature. I was running things through my head of what it could be and did a visual inspection but couldn't see any belts that were tearing/cracked/broken or any hoses that were torn or loose.

When I arrived at the dealership to schedule an appointment and leave it for them over night to diagnose, the service manager hopped in the car and revved the engine up to around 3-4k rpm. When he did that with the hood up, I could once again hear the whine and smell the smell. It seemed to originate somewhere from the middle to the front/middle of the engine compartment. Upon closer inspection he and I both could smell that smell coming from the alternator area. His first reaction was that the alternator was burnt out.

I do know in recent weeks with my mom's car, that when starting it, I have to hold the key in the ignition position for an extra 1/4 of a second for the engine to start. It seems like putting these things together could be the cause of that. My mom also reported this morning that when she sat in stoplights the car acted as if it was wanting to 'give out' while idling. When she said that, I was wondering if it might not be PCV valve related. The dealership had flushed the carbon out of it last year, rather than replacing it when it was having idling problems and wanting to idle to idle to halt.

Anyone here have thoughts/ideas/suggestions?

Brad

Reply to
Bradley Walker
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One potential source of smell is grease or oil leaking on exhaust system. This happened to me and is easily seen by looking underneath for burnt spots on exhaust. Car could have multiple problems.

Frank

Reply to
Frank

Shorted alternator diode will cause a whine and might very well cause the smell.

Typically, a shorted diode will still allow the alternater to charge the battery marginally, but at the same time will discharge the battery quickly if the engine is not running. Have you had to jump the car lately?

A tech can sort this out pretty quickly. He needs to disconnect a battery cable and measure the current with the engine off. I would expect a reading of 1's to 10's of milliamperes if the alternater is good and something like 2-3 amperes if it has a shorted diode.

Reply to
Jim Stewart

It's definately a bad alternator. The dealership called and are replacing it for $233 (including labor). The car hadn't needed a jump at all as far as I know, the only indication was that when it idled at a stop light my mom said it felt like it wanted to just stop.

Reply to
Bradley Walker

Did the alternator fix the problem? I've worked on auto electronics for years, and I've never heard a bad alternator make any noise. They usually quietly stop working or otherwise go bad and stop charging, drain your battery when off, etc.

Reply to
Zootal

I'll find out today. My mom is scheduled to pick it up around noon, I'll definately let you know.

Reply to
Bradley Walker

It's a good troubleshooting key. A shorted alternator diode causes the alternator's rotor to "cog" since rotation of the shaft will be much more difficult as the rotor's magnetic field moves across the winding with the shorted diode. The cogging is what causes the whine.

The bad smell was probably from that winding cooking, since it's full output was being short-circuited by the diode.

Often, the battery will go dead since the shorted diode provides a path for battery current through the winding even when the engine is stopped. The diode normally functions as a one-way valve allowing power to charge the battery, but not to flow back into the alternator when the engine is off.

You used to be able to replace the diode pack for about $30 in parts. I haven't had to deal with the issue for 20 years so I don't know if you could still buy one. The job is pretty labor intensive so I doubt that you'd see many shops doing it anymore.

Reply to
Jim Stewart

That was the correct issue, however this happened once to my mom a month ago but the issue went away. It didn't reappear until yesterday and was verified as being the issue by the shop. She was billed for $239 for labor and an entirely new alternator, not just the diode.

Reply to
Bradley Walker

I'm not 'directly' a mechanic; but I've seen about every version of alternator failure at work. (I'm a two-way radio tech)

Alternator problems often show up as two way radio problems because many failures produce "dirty" power that drive microprocessor-controlled transceivers batshit. Most people don't realize that alternators *do* have brushes (riding on sliprings) because they don't usually wear out. "Chattering" brushes can make ungodly audible noises that also produce massive amounts of electrical noise.

Depending on belt wrap and position; a shorted diode can cause little "stalls" as the rotor turns that can cause a squeal that's sort of like a plain old loose belt.

My old Jeep would lose seals in the alternator bearings and squeal like hell about every two years. (it too spent many hours trying to be a submarine;}

Reply to
nobody

Two Subaru Legacys, three alternators with the whining problem. It seems that this alternator has a design flaw. (a fourth alternator broke the usual way: worn-out brushes)

Yes the whining problem is a shorted diode. I opened up one alternator and found the faulty part. ( Do not try this without having the shop manuals, there's a trick.) The shorted diode causes one of the three coils to short circuit. Excessive currents flow through this winding. It causes the noise by magnetostriction, and it causes the whole alternator to overheat, eventually making the rest of the components to fail. With the shorted diode, the Failed battery indicator does not show in the dash, but the battery will not charge so the car will stop after a while...

As a test I cut open the diode and reassembled the alternator. No more noise, no more heat, the battery did recharge. However the remaining two diode sets were overstressed and second one shorted after a couple of weeks.

The diodes are press-fitted into plates. Impossible to change one diode. Changing a plate? Well, the Subaru dealer was asking more for a single diode plate than it costed to have a rebuilt alt. (not at the subaru dealer) Alts rebuilt by Delco have a lifetime warranty.

It is easy to find if your alternator charges properly. Get a $!0. digital multimeter, and measure the voltage at the battery posts. If the charger works, the voltage will be at around 14.1 volts with the engine running.

Felix

nobody wrote:

Reply to
felixc

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