You don't need to, but in order for the alt to work you need a resistor across two pins in the dash plug as shown below.
It completes the circuit, since I kept my under dash harness and most of the underhood harness I just went that way as it was easy and easy to go back stock. I am sure you could loop it back somehow at the alternator, but I would not be able to tell you how.
I thought I read that the resistor is what tells the alt to send the voltage.The resistor is not strictly necessary for the alternator to charge; as long as the 2 wires are joined. Resistance only becomes an issue when the VR tries to turn on the warning light; if the wires are simply shorted, the VR may draw too much current. The best solution is to simply copy the original bulb & resistor configuration from the original cluster to whatever you end up using.
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Another question, what about converting to a one wire setup or a gm style alternator? iRRc you can run GM style Alts with the Holley.
I'm sure you can no problem, but I have not tried as I kept my stock brackets.
The wires carry voltage/current. Resistors resist current & drop voltage. The voltage regulator will turn the alternator on with probably 8V (maybe even less, depending on each VR's particular threshold) on the LG/R wire so that charging can happen even (& especially) if the battery is low. So that resistor doesn't hurt anything in normal operation. Its purpose is to complete the circuit if the bulb is burned out, which must be expected to happen occasionally. Without the resistor OR the bulb, resistance becomes infinitely high meaning 100% voltage drop, so the key-on voltage from the R/LG wire would never reach the LG/R wire and the alt. doesn't turn on. But if you jumper R/LG (or any other ~12V source) to LG/R, the alt. WILL turn on as long as that feed is above its threshold.
All alternators work essentially the same way, so you could use virtually any brand/model/style you want. Most VRs do, other than some working on the GROUND side of the rotor (like Ford 1G) and variations on the indicator circuit. 1-wire (misnomer) regulators for these 3G alternators don't work any better, DO cost more (because not as many are made), and still require at least 2 wires to the alternator (often 3 if the external Stator circuit's Wh/Bk wire is retained), so they're pointless. If you were building 1,000 vehicles a day and could buy 1-wire VRs at the same price as the Ford design, you might save yourself a few bucks on 1 fewer wire to build into each VR connector, but you're not. You have all the wires, and they work, so it's cheaper & more-reliable to just use the correct VR, which also puts slightly less draw on the battery when the vehicle is parked & OFF.
Lots of good info, Thanks!The wires carry voltage/current. Resistors resist current & drop voltage. The voltage regulator will turn the alternator on with probably 8V (maybe even less, depending on each VR's particular threshold) on the LG/R wire so that charging can happen even (& especially) if the battery is low. So that resistor doesn't hurt anything in normal operation. Its purpose is to complete the circuit if the bulb is burned out, which must be expected to happen occasionally. Without the resistor OR the bulb, resistance becomes infinitely high meaning 100% voltage drop, so the key-on voltage from the R/LG wire would never reach the LG/R wire and the alt. doesn't turn on. But if you jumper R/LG (or any other ~12V source) to LG/R, the alt. WILL turn on as long as that feed is above its threshold.
The precise voltage on LG/R is irrelevant as long as it's above that threshold; it's not what the VR looks at to regulate - only whether or not to energize the rotor. Its reference voltage is the Y wire compared to case ground (which is why the case mounts must be clean through the bracket & head to the block where the B- cable must be securely attached, all through clean metal).
The only problem with a jumper wire (no resistance) is when there's some charging fault detected by the VR and it tries to ground LG/R which should turn on the indicator light. If there's 0 resistance because both the bulb & resistor have been bypassed, the VR MIGHT draw more current through that circuit than the VR can tolerate, damaging the VR. But a Ford VR is built not to do that - it can tolerate a short circuit from R/LG to LG/R through itself to case ground. It's only the aftermarket ones that might not be able to.
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All alternators work essentially the same way, so you could use virtually any brand/model/style you want. Most VRs do, other than some working on the GROUND side of the rotor (like Ford 1G) and variations on the indicator circuit. 1-wire (misnomer) regulators for these 3G alternators don't work any better, cost more (because not as many are made), and still require at least 2 wires to the alternator (often 3 if the external Stator circuit's Wh/Bk wire is retained), so they're pointless. If you were building 1,000 vehicles a day and could buy 1-wire VRs at the same price as the Ford design, you might save yourself a few bucks on 1 fewer wire to build into each VR connector, but you're not. You have all the wires, and they work, so it's cheaper & more-reliable to just use the correct VR, which also puts slightly less draw on the battery when the vehicle is parked & OFF.
