# Alternator is putting out 16.3 volts **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** batteries, toyota\ **Created:** [June 25, 2019, 10:58pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015 "2019-06-25T22:58:23Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![old\_mopar\_guy](https://avatars.discourse-cdn.com/v4/letter/o/6bbea6/32.png) [@old\_mopar\_guy](https://community.cartalk.com/u/old_mopar_guy)\ **Post date:** [July 4, 2019, 2:23am UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/21 "2019-07-04T02:23:03Z")
Now I’m worried that the biggest fireworks display will be in your driveway tomorrow! When are you going to take this car in to a qualified mechanic and spend a few bucks to have him fix it? Running jumper wires without even having a wiring schematic for this car is lunacy. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [July 4, 2019, 2:36am UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/22 "2019-07-04T02:36:06Z")
> [@BOuLDeR7](#): > > So the white wire going to the 3 wire alternator plug is the sense wire and is supposed to be a wire going to the battery (i assume with a fuse in it). This wire was showing around 9 volts yesterday and when I checked it today it showed less than 1 volt. Take a look at the circuit diagram Tester posted above. The “S” wire is pin number 3, right? Note how it connects directly to battery + through the alt-s fuse? So if you are measuring anything other than battery voltage on that pin - wire harness problem - alt-s fuse problem - main fusible link problem - grounding problem (the battery ground terminal must be at the same voltage as the alternator case ground ( within 100 mv) The alternator won’t output the correct voltage if the sense pin isn’t very close to battery voltage. Follow that circuit point by point from the battery + to the alternator S pin, figure out where the break is. ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [July 4, 2019, 3:38am UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/23 "2019-07-04T03:38:40Z")
Nothing like starting at the back of the book and working forward… At some point the reality that this whole thing was a 5 minute fix may set in. Or not. ---
**Author:** ![researcher](https://avatars.discourse-cdn.com/v4/letter/r/edb3f5/32.png) [@researcher](https://community.cartalk.com/u/researcher)\ **Post date:** [July 4, 2019, 3:56am UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/24 "2019-07-04T03:56:44Z")
Just as a test, pull the three wire connector and turn the ignition ‘on’ but don’t start the engine. If the ‘charge’ light is still on you have a shorted lead to that light. One place where the short might be is (if you have day time running lights) in the relay shown in 'tester’s diagram. I am wondering how having that lead shorted to ground would affect the regulator and turn the field full ‘on’. It appears having the field fully ‘on’ is the crux of the problem you are having. P.S. On further thought, I can see how the alternator would self activate. The diode trio shorted to ground would cause a DC current to flow in the stator windings. The magnetic flux of the stator would react with the rotor winding which would be rectified by the bucking diode causing a steady, building current in the field winding. It is a feed back loop that turns the alternator fully ‘on’. You haven’t stated the mileage on this Matrix so I am assuming 100K miles. If you have the daylight running light feature, the relay would have been running 2500 hours enough time for the relay coil winding to burn out and short. If you do have the daylight running feature, find that relay and unplug it. ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [July 4, 2019, 4:32am UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/25 "2019-07-04T04:32:20Z")
To begin diagnoses you need to measure the voltage at the battery posts, the battery clamps and the output terminal on the alternator. ---
**Author:** ![mperry\_153483](https://avatars.discourse-cdn.com/v4/letter/m/a4c791/32.png) [@mperry\_153483](https://community.cartalk.com/u/mperry_153483)\ **Post date:** [July 4, 2019, 5:45am UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/26 "2019-07-04T05:45:44Z")
Good job. For now, I’d ignore the light. Maybe solder a couple wires to the battery posts, temporarily run them inside the car and hook to your ammeter. That will eliminate all other faults and give a true battery reading. If the voltage is still reading extremely high at the battery, I’d suspect it could be shorted internally or the alternator (though new) could be faulty. Sometimes plates flake off. If it’s staying below 15V, all may be OK with that circuit and other diagnostics are needed. There are other reasons it could read high, but those are the ones I’d still suspect. A friend once connected the generator (yep, that long ago) directly to the battery. The problem pointed out a faulty voltage regulator in that case, though it had been replaced twice. ---
**Author:** ![It\_s-Me](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/it_s-me/32/12660_2.png) [@It\_s-Me](https://community.cartalk.com/u/It_s-Me)\ **Post date:** [July 4, 2019, 6:41am UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/27 "2019-07-04T06:41:38Z")
> [@mperry\_153483](#): > > Maybe solder a couple wires to the battery posts, temporarily run them inside the car and hook to your ammeter. Please don’t do that. ---
**Author:** ![mperry\_153483](https://avatars.discourse-cdn.com/v4/letter/m/a4c791/32.png) [@mperry\_153483](https://community.cartalk.com/u/mperry_153483)\ **Post date:** [July 4, 2019, 6:45am UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/28 "2019-07-04T06:45:12Z")
> [@It\_s\_Me](#): > > Please don’t do that. Meh. It’s as safe as testing battery voltage directly and he’ll have them for an hour, tops. Since the problem is intermittent when driving, he needs to see if the dash is display the proper voltage. ---
**Author:** ![It\_s-Me](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/it_s-me/32/12660_2.png) [@It\_s-Me](https://community.cartalk.com/u/It_s-Me)\ **Post date:** [July 4, 2019, 7:55am UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/29 "2019-07-04T07:55:20Z")
> [@mperry\_153483](#): > > temporarily run them inside the car and hook to your ammeter. > [@mperry\_153483](#): > > he needs to see if the dash is display the proper voltage. How are you going to measure voltage with an ammeter ? Also I don’t know of any ammeter in a car that can measure the 500+ amps of a battery ---
**Author:** ![mperry\_153483](https://avatars.discourse-cdn.com/v4/letter/m/a4c791/32.png) [@mperry\_153483](https://community.cartalk.com/u/mperry_153483)\ **Post date:** [July 4, 2019, 6:34pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/30 "2019-07-04T18:34:49Z")
Sorry… his hand held ammeter (Ohm/volt meter). ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [July 4, 2019, 6:56pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/31 "2019-07-04T18:56:35Z")
Do you even know the difference between amperes and volts . . . ? ---
**Author:** ![BOuLDeR7](https://avatars.discourse-cdn.com/v4/letter/b/c5a1d2/32.png) [@BOuLDeR7](https://community.cartalk.com/u/BOuLDeR7)\ **Post date:** [July 4, 2019, 8:33pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/32 "2019-07-04T20:33:09Z")
I pulled the “alt-s” fuse and measure the voltage on the sense line and to my surprise it measured 0.2 volts with the fuse pulled. I figured it should show 0 volts, the schematic shows it going from the alternator to the alt-s fuse and to the positive battery terminal. When I measured the voltage on the sense line with the fuse in it was all over the place from around 2 to 12 volts checking at different times. I tried to wiggle the wires as I’m checking to see if the voltage would change but I couldn’t get it to change from wiggling the wires. At any rate I watched the voltage levels with the alt-s fuse out and so far it looks good. I drove the car around a bit and the voltage was around 13.9 with a load and 14.2 without load (while moving). When I was at a stop it would drop to 12.9 to 13 volts with a load. What is the purpose of the sense wire? I know it’s supposed to let the voltage regulator know how the battery is doing but does the voltage regulator change to a higher voltage when the battery shows a low voltage? I would think this is bad because too high of a voltage can be bad. It kind of appears without the sense wire voltage it runs where it should be. it seemed when I measured the sense wire voltage and it was around 6 to 9 volts is when the alternator would start overcharging (16 to 17 volts). With the alt-s fuse out everything seems to be working pretty normal. ---
**Author:** ![mperry\_153483](https://avatars.discourse-cdn.com/v4/letter/m/a4c791/32.png) [@mperry\_153483](https://community.cartalk.com/u/mperry_153483)\ **Post date:** [July 4, 2019, 8:33pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/33 "2019-07-04T20:33:46Z")
Yes, and thank you, Mister Wizard. Writing " Pocket Digital Multimeter Ammeter Voltmeter DC/AC Resistor Ohm Voltage Multi Meter Tester Electrical Instrument " seemed a bit long winded. ---
**Author:** ![It\_s-Me](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/it_s-me/32/12660_2.png) [@It\_s-Me](https://community.cartalk.com/u/It_s-Me)\ **Post date:** [July 4, 2019, 9:04pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/34 "2019-07-04T21:04:24Z")
You need to get your terminology correct, amps and volts are different things. You keep telling BOuLDeR7 to measure voltage with an ammeter. When you should be telling him to use a voltmeter. ---
**Author:** ![Cougar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cougar/32/21348_2.png) [@Cougar](https://community.cartalk.com/u/Cougar)\ **Post date:** [July 4, 2019, 10:02pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/35 "2019-07-04T22:02:31Z")
I am getting into this thread a little late but maybe I can clear up some questions by @BOuLDeR7. You asked about the purpose of the ‘sense’ lead. It does monitor the charge level of the battery. When the battery level goes lower than it should be the sense line tells the regulator to increase the charge rate to the battery. In order to do that the alternator has to supply more current to the battery. In order to supply more current, the alternator voltage has to increase slightly higher, but not too high. There is a balance, it has to stay in a safe range so the battery and other electronics inside the car don’t get damaged due to over voltage. About 15 volts is the upper safe limit to charge the battery and keep the charging current in a safe range. When you saw .2 volts without the fuse in place you were reading some back feed voltage from the regulator and wasn’t a concern. When the sense line was disconnected and things seemed to work as they should I assume the alternator was working okay due to the way the internal regulator is designed. ---
**Author:** ![mperry\_153483](https://avatars.discourse-cdn.com/v4/letter/m/a4c791/32.png) [@mperry\_153483](https://community.cartalk.com/u/mperry_153483)\ **Post date:** [July 4, 2019, 10:04pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/36 "2019-07-04T22:04:14Z")
Ammeter is another term for a multi-meter… like soda, pop and coke. I already apologized for not making it clearer. ---
**Author:** ![old\_mopar\_guy](https://avatars.discourse-cdn.com/v4/letter/o/6bbea6/32.png) [@old\_mopar\_guy](https://community.cartalk.com/u/old_mopar_guy)\ **Post date:** [July 4, 2019, 10:10pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/37 "2019-07-04T22:10:44Z")
A hand held multimeter is only going to measure up to 1000 milliamps ( each one being one thousandth of an amp). He needs to lock his meters away and take this thing to a pro. ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [July 4, 2019, 10:14pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/38 "2019-07-04T22:14:23Z")
I’m not a wizard. But I don’t tell somebody to install an ammeter in their dashboard to measure voltage And I also don’t tell somebody to solder wires directly to the battery posts > [@mperry\_153483](#): > > Multi Meter Tester Electrical Instrument " seemed a bit > long winded. dmm . . . do you know what that acronym means? > [@mperry\_153483](#): > > Ammeter is another term for a multi-meter… like soda, pop and > coke. I already apologized for not making it clearer. No, it isn’t an ammeter is very specific . . . it measures amperes, current in other words that example with soda, pop and coke also wasn’t a good one A coke could certainly be considered a soda, maybe even a pop, although that last term is a bit archaic at this point But not every soda is a coke A 7-up certainly isn’t a coke . . . not last time I checked > [@mperry\_153483](#): > > I already apologized for not making it clearer. You may have apologized, but you didn’t make anything clearer I have a feeling you may be giving advice, when you’re really not in a position to do so. In other words, I have a feeling you lack the knowledge to be giving advice in this particular instance. I’m a professional mechanic I don’t give advice about things of which I don’t know much I don’t give medical advice I don’t give financial advice I don’t give marriage advice I don’t advise people how to raise their children Where are you getting your information anyways . . . ?! ---
**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\ **Post date:** [July 4, 2019, 10:16pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/39 "2019-07-04T22:16:32Z")
> [@old\_mopar\_guy](#): > > He needs to lock his meters away and take this thing to a pro. I agree 😃 ---
**Author:** ![old\_mopar\_guy](https://avatars.discourse-cdn.com/v4/letter/o/6bbea6/32.png) [@old\_mopar\_guy](https://community.cartalk.com/u/old_mopar_guy)\ **Post date:** [July 4, 2019, 10:23pm UTC](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015/40 "2019-07-04T22:23:19Z")
And I was just going to ask you for some marriage advice ☹ [Previous page](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015.md?page=1) [Next page](https://community.cartalk.com/t/alternator-is-putting-out-16-3-volts/143015.md?page=3)