2006 STI has seemingly random dash lights turning on.

[buffington]

I'm baffled - I have a 2006 WRX STI that has very recently started to do some very weird things.

 

Here's what happens with the dash lights:

 

While driving at any speed the emergency brake and ABS lights will flicker on for a split second. They don't stay solid, just blink on then off. Sometimes it's just one blink, sometimes it's a few in a row, but not at any discernible pattern. I'm about 85% sure it happens more when the car hits smallish bumps, but it has also blinked on when I know the road is smooth.

 

There's another set of lights that I just noticed today too: emergency brake, battery, and rear diff light. Those seem to flicker when the car hits bumps, and doesn't seem to have any other pattern.

 

The brake/ABS thing seems to happen more often when it's a bit cold.

 

Perhaps related - when starting the car, it sometimes acts nuts. With the key in the on position (prior to turning over the engine), things will seem normal, then everything can totally die, then be right back to normal again.

 

Prior to all this happening I replaced the alternator with a refurbished one. I replaced the battery at the same time.

 

Here's what I've been able to test:

- after sitting for a few days, I've checked battery voltage - 12.7 volts.

- I've checked for parasitic draw using a multimeter in circuit with the car completely off, doors closed (aside from open hood). There was minimal draw. A few milliamps at most.

- I've removed an aftermarket stereo install, suspecting grounding issues

- I've checked ground connections on the engine and at a few places inside

- I've checked fuses - none are blown.

- I've checked voltage while the engine is running. If I recall, it was close to 14 volts. I'm pretty sure I also checked current while idling but can't recall for sure.

 

What should I do next? I don't mind taking it to a dealer if I need to, but I want to have a good idea of what the problem could be before I go in. If their diagnosis is similar to ideas folks might have here I think I'll trust the dealer more.

[Mike104]

I know some have said aftermarket alternators are not good on Subaru's.  Perhaps get one from a pull and pay yard instead of the POS auto part store one.

 

Check brake fluid quantity too

Edited August 15, 2017 by Mike104

[buffington]

I know some have said aftermarket alternators are not good on Subaru's.  Perhaps get one from a pull and pay yard instead of the POS auto part store one.

 

Check brake fluid quantity too

 

I'll check brake fluid.

 

Is it worth testing the alternator beyond ensuring it's putting out the right voltage when running?

[1 Lucky Texan]

abs is very sensitive to voltage - I agree with starting with the alternator.

[heartless]

also agree on the alternator - start with that

 

and how old is the battery? old batteries don't hold a charge well, and make the alternator work overtime trying to keep up.

 

one will kill the other (bad battery will kill a good alternator, and a bad alternator will kill a good battery) - best bet is to make sure both are in good working order.

 

i had a parts store alternator give me trouble after only a couple of months... when I got it swapped at the store, one of the diodes actually fell out onto the counter.

Slapped in the replacement, then took my old stock alternator to a shop that specializes in rebuilding alternators & starters and had it completely rebuilt (more expensive, but well worth it, imho). 2 weeks later got the rebuilt alt back, put it in and never had another problem. (the parts store replacement is still sitting on a shelf in the garage - this was about 4 years ago.

Edited August 16, 2017 by heartless

[buffington]

The battery and alternator were installed at the same time. It's been a few months now, and the battery voltage appears to be totally stable. Perhaps the battery condition is such that it's masking an issue with the alternator?

 

In any case, I hear what people are saying about the alternator. I'm going to learn how to test it properly so I can feel more certain about it being the issue or not.

[1 Lucky Texan]

a month or so might also be time for a poorly tightened wire to vibrate loose...double check alt and battery connections.

[buffington]

I'm still troubleshooting this. I'm not convinced it's the alternator or the battery. I also checked brake fluid - it's where it should be.

 

After letting the car sit for a few days I tested the voltage early in the morning when it was "cold" (though 55F probably isn't really cold when it comes to batteries). 

 

Battery voltage was 12.7v.

 

Later in the day I turned the car on to test it while running.

 

With A/C on, radio on, headlights on, radar detector on, all inside lights on, trunk open (for the trunk light), engine at about 1500RPM, the voltage varied between 14.4-14.5v. Turning the A/C on or off did little to the running voltage. With all lights off, A/C off, stereo off, etc., running voltage was 15.2v.

 

Immediately after turning the car off, the voltage was 13.2v.

 

I also checked for bad ground connections or voltage drops between the alternator and battery. The voltage between the battery negative and the alternator body was around 0.04v with every accessory and AC on. Between alternator mounting bolt/bracket, and between main engine ground to battery was also 0.04v.

 

I checked the positive battery terminal to the alternator positive post bolt, the nut, and the lug on the same post: all were between 0.14v to 0.20v at around 1500rpm, with accessories. Turning the A/C on and off showed no significant changes to that reading.

 

While under full accessory/AC/lighting load I also disconnected the positive lug from the battery and there was no change. Not a surprise since the alternator is obviously producing voltage, but figured it was worth trying anyhow.

 

Based on these tests I'm pretty certain that the battery is charging fine, and that while running, the alternator is at least functional.

 

That said, I know that the tests I did won't tell me if the voltage coming from the running alternator aren't having huge microsecond dips or spikes. For that, I need to do some tests with my oscilloscope, which is what I'll probably do next.

 

I'll also be pulling any error codes in a few days when my scanner arrives.

 

In the meantime, does it still sound like an alternator issue?

Edited August 20, 2017 by buffington

[forester2002s]

Those voltage readings look OK, and would suggest no problems with the alternator, nor with the battery.

However, could your problem be with the connections between the battery-posts & the battery-clamps?

The -ve post seems to always be the one to corrode the worst, and may cause a high-resistance joint. And this could be intermittent.

Try this: With the engine running, measure the voltage between the battery-post and the battery-clamp. Should be 0V. Then wiggle the battery-clamp and attached cable.

Does the voltage remain steady at 0V?

You could also repeat this test by measuring resistance ohms, but first disconnect the other battery-clamp to avoid frying your meter.

[matt167]

Voltage should never go above 14.4V. systems are not designed to handle it.. Going to 15V suggests there is a problem with the diodes... Turn DVOM to A/C volts and see how many volts you get between hot lead of alternator and the body of the alternator.. Should be .5V or less since it's A/C.. I bet with everything off, your reading 1.5V of A/C ripple and that's why your seeing 15v

[Mike104]

I believe those that have reported an aftermarket alternator causing random lights had good voltage readings but when they replaced the alternator with a Subaru OEM one (often used from a pull and pay) have eliminated the issue.  I do believe in some cases it was the diodes that were causing the issue.

[heartless]

With all lights off, A/C off, stereo off, etc., running voltage was 15.2v.

 

i have to agree with matt167 - this is too high!

[buffington]

Voltage should never go above 14.4V. systems are not designed to handle it.. Going to 15V suggests there is a problem with the diodes... Turn DVOM to A/C volts and see how many volts you get between hot lead of alternator and the body of the alternator.. Should be .5V or less since it's A/C.. I bet with everything off, your reading 1.5V of A/C ripple and that's why your seeing 15v

 

I thought I knew how to test the A/C ripple, but quickly discovered that measuring between the alternator post (is that the same as the "hot lead") and body is the quick way of letting the smoke out of your cheapo multimeter. That happened this morning, pre coffee, and not really thinking it through. No huge loss though - I still have my good multimeter. After thinking it through I realized I had the positive test lead in the 10VADC port. While the advice was good the follower (me) of advice was not.

 

A/C ripple out of whack or not, I've had enough people suggest that 15v is too high that I'm convinced the alternator is a turd. I'm going to start working on finding a replacement that works.

 

For the sake of learning, let's pretend the alternator was good. Is there any other circumstance where I'd see the 15v I saw? For example, if some other component were malfunctioning, could it be responsible for the measured 15v? I'm guessing no since the alternator is the only component in the system that can produce voltage (if you exclude the battery, which I don't think counts by my definition).

[golucky66]

If the battery is damaged, defective, or even bad. Sometimes it can cause an overcharging condition as the ecm is trying to keep the battery at full charge but because the battery is bad, it doesn't understand why the battery won't take it's charge. And might command higher voltage.

Also, when a battery is cold. The voltage will be higher. No 15.2v. But if it's 30 degrees out. You might see 14.6-14.7 for a bit until it warms up a little

 

I'd suspect the alternator though.

Edited August 22, 2017 by golucky66

[buffington]

My ODB2 scanner arrived and I was pretty surprised to find no error codes. Maybe that helps support the idea that the alternator is bad (and not the ABS system as dash the lights would suggest).

 

I also drove around the block and logged the voltage. It ranged between 12.8v and 14.2v over a 2 mile run with AC on, lots of acceleration. There were no crazy dash lights this time so stuff was working fine. I'll probably try it again later this evening to see if I can get it to do its funky business. It's kinda hit or miss. I'll probably also compare what the scanner reports to what a multimeter is measuring in real time. Probably not safe to assume they'd be identical. I'd at least hope they'd be consistent.

[heartless]

the intermittent issue is very indicative of diodes either failing, or not having good connections. That coupled with the overly high output - yeah... time for a different alternator.

 

If you still have your old OEM one, I would highly recommend getting it rebuilt locally by a shop that specializes in doing them. Yes, it costs a bit more than buying a parts store replacement, but is WELL worth the cost.

 

Otherwise, I would try to get your hands on an OEM unit from a junk yard - have it tested, and if need be, get it rebuilt.

[buffington]

The issue occurred again tonight while I was logging.

 

I thought for sure I'd see high voltages in the logs, but it never climbed above 14.2. My first instinct was that it's possible the logging resolution wasn't enough to capture a spike, but the timestamps show about 20 entries per second. The brake/ABS held solid this time for several seconds - surely enough to show up in logs. There have been times when that combo of lights barely flickers on too - those not showing up would make sense, but not a several second light up. 

 

Anyhow, I'll be finding an OEM alternator this week. I'm really hoping it's the cause, because otherwise, I don't have a clue as to why this machine is haunted.

[matt167]

It's A/C volts that does it. It won't always show the A/C voltage as 'extra' tho it can. If you switch it to A/C volts through the system you should be able to see some although at the alternator is best..

 

I've seen 5-6V A/C on alternators still charging and running the vehicle but with weird oddities

[buffington]

It's A/C volts that does it. It won't always show the A/C voltage as 'extra' tho it can. If you switch it to A/C volts through the system you should be able to see some although at the alternator is best..

 

I've seen 5-6V A/C on alternators still charging and running the vehicle but with weird oddities

 

That makes sense. Unfortunately it doesn't look like I can log the A/C voltage (unless it's totally hidden in Dashcommander somewhere). I also think that the DC voltage it records is the DC voltage at the ODB2 port - not exactly what the alternator is putting out. There's a lot that can happen to that voltage between that port and the alt so it's probably best not to rely on that reading.

 

I've been hunting around for an alternator in the Salt Lake City area - so far the only sure thing is a new OEM alternator from a Subaru dealer. At $500 I'm much more motivated to go digging for one in a pick-a-part yard. My current alternator is still under warranty as well, so I'll probably get that swapped to see if I end up with one that actually works. That's assuming I can find my damn receipt..

[SubieRoobieRoo]

That makes sense. Unfortunately it doesn't look like I can log the A/C voltage (unless it's totally hidden in Dashcommander somewhere). I also think that the DC voltage it records is the DC voltage at the ODB2 port - not exactly what the alternator is putting out. There's a lot that can happen to that voltage between that port and the alt so it's probably best not to rely on that reading.

 

I've been hunting around for an alternator in the Salt Lake City area - so far the only sure thing is a new OEM alternator from a Subaru dealer. At $500 I'm much more motivated to go digging for one in a pick-a-part yard. My current alternator is still under warranty as well, so I'll probably get that swapped to see if I end up with one that actually works. That's assuming I can find my damn receipt..

Have you considered an alternator rebuilder? I have a 2001 Corvette and I had the alternator rebuilt because I bought an aftermarket one from O'Reilly's and it immediately freaked-out the electrical system. Fortunately I hadn't turned my OEM alternator in for the core, so I returned the one to O'Reilly's and had a local guy rebuild mine. It was less expensive and it works as it should. I will always go that route from now on. 

[matt167]

Looks like, 2004- up FXT, 2005- up WRX and All USDM STI use a compatible alternator, And both variations are expensive. The part you likely need though, the diode pack/ rectifier  looks to be about $85 and is probably available in the aftermarket. The alternator may or may not need soldering to replace the diodes. I've never done a Subaru. I have not needed to rebuild an alternator in a long time

Edited August 27, 2017 by matt167