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Discussion Starter #1
I took my car to a shop recently to have my wiring checked after putting a deep-cell battery due to this "Charging System Service Required" light I get every morning. My old battery tested weak and was giving me the light. New battery, same light. It shuts off after a minute of driving, starts right up every time. I only get the light in the morning. No other issues or symptoms. Alternator fine, pulleys fine. So the shop put on my work order:

"Testing found current battery sensor reading out of range, possible sensor damage.

Recommend:
Perform battery monitor system calibration procedure. Requires removing cables and PCM procedures."

Any ideas what this is? I feel like theyre making up some B.S. to charge me another $119 for something even Mitsubishi service has never heard of. Hard to trust anyone nowadays...

Advise? Anyone else get this light?
 

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... "Charging System Service Required" light...

"Testing found current battery sensor reading out of range, possible sensor damage.
...
If I found that a reading was high, I would also look into the sensor being correct!

So measure it yourself. Put a volt meter across the battery. I'm particularly interested in the charging voltage, so start the engine, and let it idle. The standard charging voltage is 13.8 V for lead-acid batteries. More than this, and I'd want a warning light. See what you find.

My guess is that it is over 13.8 at first, and goes down after a while.

I don't know if they are designed differently now, but alternators regulate their output voltage by measuring what is across the battery and adjusting the alternator output to suit. So they have to be connected to the battery twice: once with a thick wire for charging, and once with a thin wire for measuring. If the thin wire makes a bad connection, it will report less voltage, and the alternator will work harder to compensate. That means the battery is actually over voltage, and some other sensor could well notice.

If the connection improves with temperature, the warning light will go off after a while.

So check the connections. (Disclaimer: I always say that.) Especially if you've had battery problems, or the connections have been changed.

Generally, wiggle and prod until you get some change, and look into what you prodded.

HTH
 

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Yea I've checked anything electrical including the posts connected all the way, done that, but you mention increased temperature, I don't think so simply because yesterday I revved the engine after I started the car and got the light, it went off immediately. So it's something to do with raised RPM's..raising the volt output via higher RPM's making the light go off? I'm at a loss. But I do appreciate the reply and you made some good points.
 

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OK, it varies too quickly to be temperature. I'm still interested in voltage measurement, but I have a theory again already.

It could be the alternator "regulator" I believe it's called. Whatever, it's what implements the voltage control. My one of these, on a twenty year old alternator, is a chunky little integrated circuit mounted inside the alternator. It has an input from the battery to indicate voltage, and an output that directly regulates the exciter current (open-collector output to the low side of the exciter windings), but it's more of a bang-bang loop rather than proportional control. Typically, the voltage ends up meandering around 13V.

So. The regulator compensates for variations in battery state, electrical load, and engine rpm. If it is not working properly, the voltage could be incorrectly regulated. And it might have something to do with the engine RPM. I bought a replacement for my alternator for about £30 5 or 10 years ago and it was fairly straightforward to disassemble the alternator and fit it. The bad news is that it didn't fix my problem, and I needed a reconditioned alternator, but my problem was no charging current to the battery below 3000rpm.

Here's one for an Outlander, but I probably chose the wrong engine:

https://m.onlinecarparts.co.uk/car-brands/spare-parts-mitsubishi/outlander-i-cu-w/17400/10451/alternator-regulator.html

Or you could ask a mechanic to diagnose the problem properly, and this was exactly what the guys had in mind when they made their recommendation.
 

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Discussion Starter #5
Funny you should mention that the alternator/battery shop I took it to said it may be the voltage regulator but he wasn't 100%, I just didnt want to spend money on "maybe's" but it seems that may be the cause as everything else tested ok. I was more interested if there was some magical "calibration procedure" for my vehicle with the PCM.

Either way, cheers :)
 
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