Too much volts ????

[jondee86]

I had the battery out of the car for a few weeks, so charged it up
before dropping back in. Now, I have an odd situation with the battery
"check" light on the dash. At idle it is off, but give it a few revs, and the
light comes on !!!

If I add a bit of electrical load by turning on the lights, the check light
goes away, but turns back on when the revs climb. This is pretty much
exactly the opposite of what normally happens when the battery is low.

Battery terminal voltage is 13V at idle, rising to around 15V when revved.

Is this too much volts Does the battery check light come on for high
volts as well as for low volts ?? Car runs fine and nothing else has been
touched since it last was running about a month ago.

Cheers... jondee86

[Bling]

13v sounds about right for idle, never checked mine under revs, but it should get to at least 14v under load so 15 is probably fine.

can't help solve the problem tho

[rollaholic]

hows the alternator?

[Leon]

I've had an AE82 and an AW11 have an alternator failure that meant it overcharged as soon as you got above idle. Though, all the idiot lights came on, not just the alt light.

[QikStarlie]

probably getting a little high. i had one that would creap up to 18v! at that point the ecu would shutdown.

[matt dunn]

Does the battery check light come on for high
volts as well as for low volts ?? Car runs fine and nothing else has been
touched since it last was running about a month ago.

Cheers... jondee86

Yes some of them will come on if there is too much voltage,

or is there is too much difference in voltage between the output stud,
and the voltage sensing wire in the 3 pin plug.

[jondee86]

Yes some of them will come on if there is too much voltage,
or is there is too much difference in voltage between the output stud
and the voltage sensing wire in the 3 pin plug.

I've checked fuses, battery connections and the alternator plug, but
the light still comes on. Seems to be like the voltage sensing circuit is
switching due to a slight over-voltage... maybe an extra 0.5 volts. I can
vary the intensity by changing the revs... like it was on a rheostat.

Matt, do you see any problem in leaving it as it is for a while ??

Is an increase in voltage a sign that the regulator section is in need
of an overhaul ?? This car is not a daily driver, so it is not a biggie to
pull the alternator for testing.

Cheers... jondee86

[matt dunn]

put a jumper wire from the main Batt stud to the heavy white sensing wire in the 3 pin plug and see if it fixes it.

If it does not, then the alt is faulty.
Could be the reg, or possibly even one of the diodes,
although diode failures in those alternators are not very common.

[Crimson Tears]

15 volts is definitely too high. Sounds like the regulator has packed up

[jondee86]

Toyota 101 for charging systems states a battery voltage of
14.5V +/- 0.6V @ 2000 rpm with all other electrical loads off.

When the regulator temp is above 80 degF (about 30 degC)
the range is 13.0 - 15.5V.

So 15V measured on a hot engine is not excessive. My concern
is that something in the regulator might be on the way out. If so,
I and would like to catch it before it fails, and perhaps causes
collateral damage to other components.

Cheers... jondee86

[strx7]

most vehicle run between 13.8 and 14.8 volts. if running a vehicle with electric fuel pump, the fuel pump loves getting over 14V compared to the 12.something it would get from the battery.

[MAGN1T]

14.2 is the max you should see on ANY car. If you have a valentine one it will blow up at 15 volts, so will other electronics.

Probably, as above, needs a new regulator.

[RickGT]

14.4v is the general charging voltage without load

[MR2SIK]

so 15v is too high or not??? cos thats what mine sits bang on all the time...

[jondee86]

The Toyota 4A-GE Repair Manual states :

With the engine running from idle to 2000 rpm
Standard voltage:
13.9 - 15.1V at 25 degC
13.5 - 14.3 at 115 degC

So I would say that 15V is at the top end of the acceptable
range, and unless there is some other associated problem,
I would leave it alone.

In my case, the battery check light is flickering on and off,
and I would like to find a cure for that

Cheers... jondee86

[matt dunn]

In my case, the battery check light is flickering on and off,
and I would like to find a cure for that

Cheers... jondee86

Yes, you could live with the 15v if you want,
but the light on is a symptom that something is wrong.

Have you tried jumping from B+ to sensing ?

[jondee86]

Matt, I won't have a chance to check that out until the
weekend, and then I'll post up the results.

Cheers... jondee86

[MAGN1T]

Yes, you could live with the 15v if you want,

15 volts will fry you battery , will need constant topping up with distilled water.


The max voltage has nothing to do with the car or the model, it's to do with the battery.

[slighty_sykotic]

Yes, you could live with the 15v if you want,

15 volts will fry you battery , will need constant topping up with distilled water.


The max voltage has nothing to do with the car or the model, it's to do with the battery.

I had a mr2 that would give 15v all day every day. (measured with fluke multimeter) And my battery nor valentine 1 ever exploded.

Valentine ones are built pretty well.

And my battery was pretty old and was going fine, no loss of fluid, no boiling etc

[MR2SIK]

When I snapped my alternator belt, I noticed the decline in performance nearly instantly, at 12v it was spluttering and running like a bag of shite.