I recently installed the lighter weight ~1986 Toyota 4-Runner alternator onto my new SB stroker 410, cast iron heads. I also installed a new AutoMeter Volt meter gauge... by-passing the rally dash alternator gauge. I've also purchased a new Optima Red Top battery (trunk located.. replacing the old one after past ~12 years).

I purchased a brand new DENSO (not remanufactured) from AUTOZONE... lifetime warranty. This alternator has an internal voltage regulator, so, I removed the firewall voltage regulator.

I also purchased the AR Engineering Pigtail (AR016), as well as the AR022 SB mounting brackets.

Headlights and turn signals are much better (no more dimming or slow blinking at idle). But, I've observed the voltage reading on the new AutoMeter gauge to be about 15-15.5 most of time, slightly lower... about 14.5-15 with heater and lights on.

I tested the alternator and it reads the same as my new voltage gauge,,, 14.5-15.5... avg 15.

Any suggestions what could be the problem? Shouldn't the voltage read only between 12.5-13.5 at most?

Advice truly appreciated.. I don't want to have electrical problems.

Might be a touch high but not really out of line. Most alternators are designed to charge at 14.7 volts. They have to operate above battery voltage in order to drive current into the battery. My battery charger runs 14.7 when it first turns on then dials back to 13.5 when fully charged.

That alternator uses a "sense" wire so it knows what voltage the battery is at. Where did you connect that "sense" wire? Do you have a bypass wire directly from the alt to the battery? If you connected the "sense wire" to the alternators battery + lug you really need to do the amp gauge bypass and have a 10 gauge or larger wire run from the alternator to the battery.(or starter relay) If there is a lot of voltage drop in the wiring and the + stud on the alternator is showing low voltage, then the alternator is going to think the battery is low and increase the output. This is the downside to this style alternator.

I don't have a solution, but agree that is too high.
found some modern parts spliced into my old car have overcharging protection and if it hits 15 volts it doesn't let them run.

make sure its grounded well. if the case on the alternator isn't grounded due to paint on the brackets the regulator cant regulate. also make sure you have a good positive wire so it can push the right about power through to the battery. a high resistive connection will cause some grief as well.

That sounds right Mitch. I had an old stock style alt. tested at Autozone recently. It put out 14.5 amps. Perhaps your gauge is slightly off. You can always take the alt. to get tested to see what their equipment says.

15.5 v is to high. If the ground side (alt case) has voltage drop to the negative terminal of the battery it will overcharge. Same issue if the power cable to the positive of the battery has voltage drop. The voltage sense circuit of the regulator reads the battery voltage as being lower than it actually is. If this condition occurs, the field current will increase. This will cause output voltage to rise out of range.
Doug

i always like to see 13.8-14.2 [or close] volts.
15 is getting too high, in my opinion.

The location of your sense wire is key. If located at your starter relay it should sense the voltage currently be demanded. If the demand is light it should charge less. If your battery has a weak cell it will rmain high. I think the charge wire from alt. should go direct to batt. or starter if stock setup and not running a ford soleniod .This is a good read to explain .
http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml

Battery charging voltages will change with temperature, not sure if that alternator you have has that ability though.

https://batteryuniversity.com/learn/article/charging_at_high_and_low_temperatures

Charge voltage will be higher than the float voltage, 14.8v @70 degrees F. Once you start the car the charging system has to top off the battery quickly so the charging voltage will be high, automotive starting batteries are designed for this. Once it gets close to fully charged it'll drop down to what's called a float voltage, this is the13.8v @70 degrees F or so you see bandied about. As temps rise both of those voltages will drop, as temps get lower both of those voltages will rise. There is no one voltage that should be correct all the time.

All -- I truly appreciate everyone's replies and advice. Once I get it figured out, I'll let you know.

Mitch I have had the Yota/Denso alternator for about 5 years now and mine is usually 14.8-15 volts with zero issues on the rest of the system. My battery isn't gassing and my 11 to 1 493 cranks over like my 4 cylinder daily driver does. So I really don't see a problem

Gus

fourgearsavoy... T/Anks for the input... that sounds encouraging.

A crucial point is the tolerance of DC voltage measuring device...
For example, a precision Fluke multi-meter has a tolerance of +/- 0.5%..
But a typical automotive DC voltage gauge has a much wider tolerance up to +/- 5.0%.. or up to a 10% window.....

Just my $0.02...

It is certainly true of the AutoMeter voltage gauge I have. Compared to my work Fluke, which is regularly calibrated, it's way off.

A Fluke multi-meter is guaranteed to have a tight tolerance...
If your Fluke is off significantly even when recalibrated...
I would question the calibration procedure, by whom?
And if still off alot perhaps the Fluke is an older 1 that has some internal components changing value...

Just my $0.02...

My fluke is fine, it's the Autometer gauge that's off. I used to calibrate test equipment in the Navy and it's been my experience that Flukes are either right on or replaced, there were no adjustments to be made.

i was just thinking about the gauge reading [slightly ?] high, maybe it's the gauge and the alternator should be tested with a fluke meter. [i have several flukes]
you guys must have read my mind. [what LITTLE is left. ]

Just take the alt. to Autozone and let them test it for you. They will tell you the specs.

I have a rebuilt 14668 Denso alternator. it runs at just below 15V pretty much the whole time I'd guess it's a 14.9V set point on the regulator). This is on my old truck though and I don't drive it often, the big battery might not be fully charged.
I've had this alternator on my truck for atleast a year and it's been fine, the battery is fine, I bypassed the Ammeter and installed a voltmeter.

Another thing to think about, the Voltage Regulator set point. Here is one for the same style alternator and it's a 14.6V set point...
https://www.maniacelectricmotors.com/80904406.html


I also found this, notice they seem to set their alternators to 14.9V
https://www.powermastermotorsports.com/why_run_an_alternator_a.html