17-18 Volts at the Battery
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97Run-Man
New member
You're voltage regulator is internal to the alternator. The easiest solution is a new alternator. Do it soon cause batteries are not supposed to take that voltage. They won't last long, at least not from what I have seen first hand.
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TheDurk
Elite Member
Check your three connections at the plug at the alt, especially the Sense wire (white wire on Pin 3) and also the Alt-S fuse. Bad Sense connection tells the regulator to run flat out whether it needs it or not.
Ignore this and you run the risk of coming back here and whining you changed the alt and it still didn't fix it. Seen a few of those.
Ignore this and you run the risk of coming back here and whining you changed the alt and it still didn't fix it. Seen a few of those.
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The TheDurk's response made me to explore more about the alternators (I am bad at electronics) and came across this article
wilbo666 / Toyota Alternators
wilbo666 / Toyota Alternators
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RAD4Runner
Senior Member
Alternator that tests good on the bench but does not get proper "S" signal will put out too much voltage.
Battery at 16.8Volts with engine off may mean:
1) Bad battery.
2) Bad multi-meter. Did you try another meter?
+1
many people like to replace parts, instead of doing their homework troubleshooting, because it's easier... but costly.
the alternator tested good 14.3volts with another volt meter .
with the vehicle cold put head lights on see what the meter reads. or use scan tool etc . then I would expect 12 volts not any more than 12 volts
ENGINE OFF FOR MORE THAN 5 HOURS / ENGINE OFF WHEN MEASURING.
if more than 12 volts the meter is junk .. you can also measure other batteries that you have like a 9volt battery.
with the vehicle cold put head lights on see what the meter reads. or use scan tool etc . then I would expect 12 volts not any more than 12 volts
ENGINE OFF FOR MORE THAN 5 HOURS / ENGINE OFF WHEN MEASURING.
if more than 12 volts the meter is junk .. you can also measure other batteries that you have like a 9volt battery.
TheDurk
Elite Member
Was that right after you turned the motor off? Try turning on the high beams for a minute or so, turn them off and then check voltage. If still that high, it is very weird.
Check again with high beams back on.
I repeat, check your alt wiring, especially the Sense circuit.
This may help:
http://tacoma.site40.net/4Runner_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/014cs.pdf
Do you get battery voltage on Pin 3 of the alt plug with engine off, key on?
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LittleCaesar
New member
Invest in a Fluke DVM. Expensive but leaves no electrical guesswork.
Volt meters, even bench tests aren't the total gospel on alternators. I've replaced one that tested fine at 3 different battery test stops and 2 different bench-test machines. The symptom was constantly flickering lights. I did the big 3 upgrade, I checked all the grounds, did everything else first - but it was a bad alternator that looked ok when tested. *shrug*
19963.4lsr5
New member
When I shut off my truck it takes at least 30-45min for the battery voltage to come down below 12.9v.
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