Resistor in "Exciter Wire"

[NCBeachBronco]

Hi
Fairly new to forum, but had my Bronco since '97. Got tired of watching it rust, so its been a project for the last 3 years.

I'm swapping out the factory alt/external VR for 3G 130 amp Alternator with internal regulator from Power Master.
It came with a resistor in a bag saying to solder it in the "REG S" wire...why????
Read some forums on with or with out idiot lights, parallel to the light in case bulb burns out, to put resistance in the circuit... still confused.

Thanks

 

[Rustytruck]

http://www.powermastermotorsports.com/078_IS_125.pdf

 

[DirtDonk]

That's very strange. Never seen that.
Guess I'll have to go look at some later model factory diagrams, but I've never heard of a resistor directly in-line on that wire. As a bypass for the indicator light on the dash, yes. But as a resistor for the alternator's S wire? Never seen that.

Normally on the Ford circuits I've seen the resistor is used as a bypass in case the bulb burns out. As you can see in their diagram, if the bulb burns out the way they have it wired the power will stop and your alternator will no longer charge.
The resistors in Ford circuits are there so that the voltage going around the lamp is less than that going through the lamp. So the lamp will still work as expected, but if it ever burns out there is enough power going around it to keep the alternator charging.

Personally, I would either call and get a clarification from some tech guy there, or just leave the resistor out. None of us that I'm aware of have ever used anything but a direct line wire to the S connector. No reason for lowing the voltage in that wire that I can think of.

And without an indicator light, it just works like any other alternator install in a Bronco.
If you call them let us know what they say.
Maybe ping Viperwolf1 or Steve83 to see what they have to say about that diagram.

Paul

 

[NCBeachBronco]

Yes Rusty, I have seen that before (came with my alt), but it doesn't tell me why it's needed

Thanks though

 

[NCBeachBronco]

Thanks Paul - was thinking of trying it w/out the resistor.
Already called PM - had to leave a message

 

[DirtDonk]

Yeah, the only reason I was saying to call anyway, is just in case they're doing something odd with their internal regulators.
They make some good stuff, but I don't know what, if anything, they change.

On a standard Ford 3G you don't need the resistor inline whether you have a light or not.

Good luck.
Oh, and welcome to classic too finally! How far along are you in the project. Seeing any light at the end of the tunnel?

Paul

 

[NCBeachBronco]

According to Chris at PM, their alternators like to see resistance in the exciter circuit and seems to help the alternator last longer...

Bronco has been back on the road for a little over a year now (with a lot of WH parts), but still dealing with a few issues. Main one is keeping engine cool. Was going to go with electric puller fan-why I was switching alts, but still don't have quite enough room for it. I have Vintage Air and the condenser took some valuable real estate. Did some minor cutting on the lower part of core support and now have room for fixed pitch blade, so gonna try that.

 

[Steve83]

The resistor is only there in case the bulb burns out - it has no impact on how the alternator works, or how long it lasts. Click this & read the caption:

 

[DirtDonk]

Well that's good to know NCBeach. I'm with Steve on the the resistor thing obviously, but that's for a stock/standard unit. No way of knowing what they do to theirs (likely nothing?) or what they know (probably something!;D) but hey, that's why we read the manufacturer's instructions!

Be interesting to see what, if anything, we can tell from this if you use one.
But from the sound of what Chris said, it sounds like you could go either way and have a functioning alternator. But since they go to the trouble of supplying it, you gonna use it?

I'm guessing they say to leave it off if you have a dash light, because they figure it already has resistance in the circuit. Even though it's likely a different value from their supplied resistor.
Otherwise I'm not sure how they'd know what resistance value your original wiring had. Different vehicles of different years have different lamp circuits. I'm "assuming" here, but I assume the resistance varies between them.
But you know what assuming gets us...%)

Paul

 

[Steve83]

The resistor is only needed if the circuit HAS a bulb. If there's no bulb, don't install the resistor. The circuit doesn't NEED resistance - the VR will work with a straight wire, which should have nearly 0 resistance.