My alternator dying?

[wparsons]

Originally Posted by stockysnail

The MAF cleaning didn't cure it. Last night the voltage was going down to 13.0 and went up to 14.3 which I haven't seen it go over 14.2 until last night.

Codes did not reappear yesterday nor this morning on the way to work.

If you hold it at like 2000rpm, what's the voltage?

Does the voltage drop before, or after, the engine sags?

[DoomsdayJesus]

I have a voltage meter on my radar detector, the voltage hunts all over the place anyway depending on the electronics. It'll dip like crazy if you're playing music, rolling down the window, if the fan cycles, AC turns on or off... probably more if your battery can't provide the instant power the car requires and it leans on the alternator more often. That may be the side effect of using a lightweight battery.

If you use a stock battery, it takes a little while for a standard battery to provide power on demand. AGM batteries like optima and similar can provide it a little faster. I have absolutely no idea how a motorcycle battery would work for that purpose but it's entirely possible you've overtaxed the alternator.

Gas quality was my problem briefly, I just went back to Costco but I'll probably throw a tank of shell in there every so often. FYI, I learned the detergent they use for top-tier status is Lubrizol.

[stockysnail]

Originally Posted by Ultramaroon

I don't understand. Are you going only by the voltage reading, or is it still stuttering? Bring it by Saturday and we'll dig deeper. I'm not against swapping in my alternator to troubleshoot but we can do much more before we go there.

It hasn't stuttered in a few days so currently going off the voltage reading.

[stockysnail]

Originally Posted by wparsons

If you hold it at like 2000rpm, what's the voltage?

Does the voltage drop before, or after, the engine sags?

If I hold it at 2000rpm, the last couple days it's usually at 14.1 or so within .1. Sometimes the voltage will drop but it's not happening as frequently the last 2 days since spraying the MAF with cleaner. When it does drop the last couple days it's been as high as 14.3 and as low at 13.0, but I can't keep my eye on it while driving. I tried to have it parked in my garage and rev it and it seemed fine.

[Ultramaroon]

Originally Posted by stockysnail

If I hold it at 2000rpm, the last couple days it's usually at 14.1 or so within .1. Sometimes the voltage will drop but it's not happening as frequently the last 2 days since spraying the MAF with cleaner. When it does drop the last couple days it's been as high as 14.3 and as low at 13.0, but I can't keep my eye on it while driving. I tried to have it parked in my garage and rev it and it seemed fine.

I suspect you're chasing a red herring but I'm game for firing up the techstream and going by the book. Here's the relevant section.

[projek_01]

If your voltage/charging system is intermittently charging, it could be worn alternator brushes. If you have over 60k miles on it, it could be a possible. Our ECUs also control the voltage regulator to turn off while acceleration to help with fuel consumption so keep that in mind.

[BlueBoy]

Apologies for reviving this ancient thread but it's the closest one I could find relevant to my current problem.


Stockysnail, did you figure out the source of your problem? I'd been using a lightweight battery similar to yours for like 80,000 km and it suddenly just died. My new group 35/550 CCA replacement battery's voltage is fluctuating between 12.11 V and 13.15 V while idling and hasn't gotten above 14 V. My battery warning light has come on and off twice and I've noticed that the battery charges when the light is off. The problem has been going on for about 2 days now and I'm wondering if it's likely my alternator. Any thoughts?

[Ultramaroon]

ECU controls charge rate. It's normal for voltage to fluctuate. I haven't yet read of any alternator failures that didn't affect power steering but just in case...


https://gt86stuff.onrender.com/t3Por...01AR909JX.html

[brandonblt2]

I had 110k to 120k miles on my brz before I replaced my alternator. Mine was making a loud rattle noise so it was easy to determine it was going bad. I don't remember it popping any cels though.

[BlueBoy]

Originally Posted by Ultramaroon

ECU controls charge rate. It's normal for voltage to fluctuate. I haven't yet read of any alternator failures that didn't affect power steering but just in case...


https://gt86stuff.onrender.com/t3Por...01AR909JX.html

Yeah, I should've mentioned the power steering failure happened then the car stopped running within 5 more minutes of driving.



I don't have both an ammeter and voltmeter to simultaneously check voltage and current, but at 2000 rpm when reading just the voltage across terminal B of the alternator to ground it reads about 5.7 V which is really low. Do you know if the voltage reading is meaningful without measuring current across terminal B simultaneously?

[Ultramaroon]

Originally Posted by BlueBoy

Yeah, I should've mentioned the power steering failure happened then the car stopped running within 5 more minutes of driving.



I don't have both an ammeter and voltmeter to simultaneously check voltage and current, but at 2000 rpm when reading just the voltage across terminal B of the alternator to ground it reads about 5.7 V which is really low. Do you know if the voltage reading is meaningful without measuring current across terminal B simultaneously?

B+ is actually battery voltage. That's a completely dead battery. Zero charging but we already know that because no power steering. I'd pull the alternator and get a beefy charger on the battery yesterday. Realize that the battery's been compromised from being so deeply drained.

[BlueBoy]

Originally Posted by Ultramaroon

B+ is actually battery voltage. That's a completely dead battery. Zero charging but we already know that because no power steering. I'd pull the alternator and get a beefy charger on the battery yesterday. Realize that the battery's been compromised from being so deeply drained.

I recharged the battery and replaced the alternator with a Bosch rebuild. Problem solved. Thanks for the replies.

[Ultramaroon]

Originally Posted by BlueBoy

I recharged the battery and replaced the alternator with a Bosch rebuild. Problem solved. Thanks for the replies.

Great to hear. Happy motoring!