New Voltage Regulator for Ford Heavy Duty Transpo F540XHD | eBay
There are 4 terminals labelled I A S F
I......is for the idiot light
A..... is for the Always Hot. Run to battery (+) with minimum 14awg or thicker
S .....is the switched hot. This is supposed to be live with the engine
running. Very little current
on this terminal.
F..... This terminal goes to One of the two Field connections on the externally regulated alternator. The other field terminal must be grounded.
There are pigtails one can get. I used individual quick connects
The Voltage regulator case must be well grounded.
There is an internal 2K ohm potentiometer for adjusting voltage. 2 screws to remove lid and access it.
I got under the semi potted potentiometer, and nipped off its legs above the potting, soldered wires to legs, twisted them tightly , ran them through a ferrite, and ran them to a remote
10 turn 2K ohm Bourns potentiometer with turns counter.
Target voltage range is adjustable 12.8 to 15.3v.
I also attached a finned heatsink from an old CPU to the underside of the voltage regulator body, adjacent to heat producing transistors, and carry a spare.
In the wiring
harness along field wire and ground wire, I added a K type thermocouple, and thermal epoxied the sensor end to my alternator casing. Can measure stator temperature with a digital multimeter or other device that accepts k type thermocouples.
Got a sensor on my battery, alternator, and voltage regulator heatsink and one channel free, so far.
With an Ammeter and voltmeter is it interesting to collect temperature data.
Low rpms and high loads and both VR and alternator temperature spike.
Battery temperature increase when high amp charging
also much higher than I expected