I installed a Toyota alternator and I'm only getting 12.89 at the alt and battery
Any suggestions?

What are you using to regulate it?

Is it a external regulator... 2 field wires..
one wire goes to switched power the other goes
to field and.... here is a diagram to check
Sorry its blurry

I'm not regulating it, can I jump the connector on the back?

Make sure the regulator is grounded

Had the same problem with a denso alt went to powermaster one wire self energizing problems gone

For a normal alternator to function you need to have a current flowing thru the field winding.
An unregulated alternator would have one field terminal to switched +12V and the other field terminal grounded for getting full current in the field winding. This will give the maximum charge current/voltage at all times.

This is the back

Going to buy one of these

I hooked it up like this with exception to the charge light, left that loose.
With car running and all accessories on I have 16.57v
So now I'm too high.
The battery is fully charged.
Any ideas?

For some reason you are full fielded.. the regulator
might be welded closed in it...if you have it wired
like you show it should be good... as you rev it up
the voltage will also if its full fielded... you might
need to take it into a shop for a regulator
EDIT
Thats why I like the external regulator

Not sure why you now how high voltage?

But I had the not charging problem with mine until I hooked something up the Lamp wire. Pretty sure I hooked it up to switched 12 volt source, definitely don't have an actual lamp. Old Toyota tech told me the lamp wiring on most of the denso alternators doubles as the energizing source (field ?) that switches on charging in the alternator, while the "Sense" line only acts as a reference point for how much charging is needed.

Some have said theirs works fine without Lamp hooked up, but mine sure didn't.

I have heard that on the 3 wire system.. most just
put a small resistor in that line to ground.. I
use the 2 wire deno alt. this uses a external regulator
which I can change out if needed

I never worked with the Toyota system but many use the idiot light circuit going to ground through the field and start the alt charging but most have a resistance wire in parallel with the alt idiot light. Once started many like the GM units with internal regulators use a diode trio that then powers the field and puts battery volts on both sides of the idiot lite and puts the lite out. This may be different since it has the output circuit and another hot 12 volts and the key on 12 volts and then the lite circuit. I would hook the lite circuit up as you can just use a resister of the same ohms as the dash lite would be. Ron

I don't know the details of this Nippon Denso alternator but yes, the lamp is commonly used to pass a small current thru the field winding. This small current creates a magnetic field that in turn creates the charging current in the big stator winding. Once the alternator has started charging it doesn't need the lamp current anymore, since it's internally feeding itself with field current, as was pointed out.

Also, some alternators may slowly start charging even without the lamp/field current, since some remaining magnetism may still be there.

Most of the older GM and Fords had a 12 volt hot all the time feed at their voltage regulators that would feed full 12 volts to the field after it started charging enough from the idiot lite and paralell resister circuit which would start it charging enough to close the field relay inside the regulator and then that 12 volts fed the field and back to the idiot lite to put the lite out since it had 12 volts on both sides of it now. The old GM and Ford 4 wire voltage regulators used in the 60's and 70's had one circuit (#1) from the ign switch that fed the idiot lite and paralell resistance wire and went to 1 terminal on the reg , then the reg had a 12 volt hot at all time feed (#2) , the third terminal(#3)was from the center of the alt stator winding that fed the field relay inside the reg , and the fourth (#4) went to the field terminal on the alt. Once the alt started turning the volts fed into the reg from the idiot lite and resistance wire went into the reg and came back out the terminal to the field and fed the field from the idiot lite and resistance wire which was enough volts to start the alt charging and then the volts from the stator winding was enough to close the field relay and feed the 12 volts from the hot all the time terminal into the field and back to the other side of the idiot lite. Basically once it was charging the 12 volt hot at all time terminal on the reg fed the field circuit through the reg and was then controlled by adding or removing resistance from the field circuit to maintain proper voltage. But without seeing the wire picture I am not sure the Toyota system works the same. When GM added the internal regulator they still used the idiot lite and still put 12 volts on both sides of it to turn it out but using the diode trio instead of a wire from the stator winding but the diode trio was fed from the stator windings where the normal diodes were tied in. Most of the systems with an idiot lite used the idiot lite circuit to start the alt charging.


And of course the one wire alt have enough magnetism in the stator and field circuits to self excite itself and then feed itself and build up to working voltage. Ron