high voltage from alternator
 

This morning on the way to work the voltage gauge bottomed out on the left and the check gauges light came on. I pulled the code and it was for low alternator voltage when i got home and checked with my multi meter at the battery and it was charging at like 17 volts. So i went and bought a new alternator, installed it and it's still charging at 15+ volts. I've read that it could be the voltage regulator in the pcm? I know the battery is good and the alternator is new obviously. So what are your thoughts on it?

Check your battery temperature sensor.

https://encrypted-tbn1.gstatic.com/i...eyLN9y9VfOXgxg

How do I check that? I can run my meter over the plug but what am I looking for? Like ohms or whatever

I found its supposed to be between 9 and 11k. I'll check it here after a bit.

Ok so after new alternator and refreshed all the grounds The voltmeter isn't registering anything but it is still cranking out 15+ volts. My conclusion is the voltage regulator went south if it's not reading anything on the dash but still cranking out a charge. When I pulled it into the garage the voltmeter read a normal 14 or so volts for a minute then bottomed out again.

"I pulled the code and it was for low alternator voltage when i got home and checked with my multi meter at the battery and it was charging at like 17 volts. So i went and bought a new alternator,"

Sounds like a wiring issue, what was the code number exactly?

Iirc it was 1682. Charging system voltage to low.

Try hooking up your DMM across the battery terminals while the engine is running and wiggle the connectors at the PCM. Watch the meter and see if there is any change. What happened with the BTS?

It was like 17.26on the 20k setting so not in the normal parameters. I'll try wiggling the connectors here and see what happens on the meter. But i suppose I'll hafta grab a sensor tomorrow

Would the temp sensor really have that much to do with it?

Did you check it at room Temperature?
(2) Disconnect the two-wire pigtail harness from
the engine harness.
(3) Attach ohmmeter leads to the wire terminals of
the pigtail harness.
(4) At room temperature of 25° C (75–80° F), an
ohmmeter reading of 9,000 (9K) to 11,000 (11K) ohms
should be observed.
(5) If reading is above or below the specification,
replace the sensor.

Yeah its been in my garage at 65 degrees for 2 days so it's plenty warm. So I got it running now with the meter on it and messing with the pcm cables. Nothing out of the ordinary. I had discharged the battery after it was overcharged by the alternator had to jump start it. With the meter on the battery posts it was charging up from 9.2 volts to just about 10 when it died and now threw the code 1492 "battery sensor input voltage too high" which I never had before. The sensor ohm'd at 17 and some change so I'll pick one up tomorrow and see what happens

I believe if you lose ground to the sensor (& through the PCM) you get P1492.

Lets back up a little bit, how do you know the battery is good, was it load tested?

Yeah it was load tested and deemed ok. I'll bring it with tomorrow when I go to the parts store and have it done again just for grins though. It's only a little over a yr old too.

The high charging voltage combined with the jump start makes me think wiring issue or the battery is SOL. Can you pop the caps to check cell voltage or is it sealed?

I can pop the caps but I dont have the tester for it. I'll grab one tomorrow when I get it load tested again and get that temp sensor.

What turbo said. It's been through the ringer it seems,
I would replace it just for piece of mind..

Yeah that might have to happen. But I'm gonna try the new sensor being it tested bad. I'd rather not have to buy a new battery unless I absolutely have to. I was waiting on a new battery till I could get an optima. We'll see what tomorrow brings I guess

I understand you dilemma, but look at it this way.
The battery was compromised and will probably not last as long as it is supposed too.
Off topic what year Optima you looking at?

Well I ordered a new bat temp sensor, and I'm gonna get a new yellow top optima. But one thing has been bugging me about this whole mess, the volt meter doesn't read a thing on the dash when it's running, but it still charges, wouldn't that indicate the pcm is bad being the cluster gets its feed from there? I found a link to a guy that had the same thing happen to him but his gauge worked the whole time. His situation proved to be a bad ground from the alternator field to the pcm after replacing just about everything including the pcm. I'm gonna check that wire but after that it's got to be the pcm imho.

So. Update. I got the new sensor in, did a bunch of wiring tracing, found nothing out of the ordinary. For grins I went and got an external regulator and installed it. The voltmeter now reads what it's supposed to, but the alternator isn't charging. It just stays running at like 12.5 volts give or take. So would that mean that the regulator in the pcm is bad as well as the ground or power circuit for the alternator also, being it isn't switching fields and charging?

Update. New pcm fixed the issue for a little bit. Started up an ran fine. Alternator was charging normally according to my dmm on the battery terminals. Then the Guage bottomed out again and now it's not charging. Got the 1682 code for battery voltage to low. I'm gonna take the alt in and have it checked. Then go from there. Where does the green with orange tracer wire go to off the back of the alternator