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Wiring questions with upgrades 81 f150

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Shankles McBullnose

Wiring questions with upgrades 81 f150

Just installed a pgmr starter and a 3g alternator and could use some clarification on some things pertaining to the ignition connection pictured. Is the junction circled in green necessary? I assume the alternator takes over the ignition once it's on. If it is, do I need any kind of diode to prevent any back feed? Is that junction The ignition switch connector? Do I also still need to utilize the I terminal on the relay?? I have so many questions

The haynes manual takes into account the stock wiring so I can only go so far with that.

There are so many different ways to go about this I've had a hard time finding one source that has done both pgmr and 3g upgrade. I've kind of had to work through what makes the most sense in terms of wiring and electricity flow.

81 F150 460/C6 600 cfm Holley

Gary Lewis

Re: Wiring questions with upgrades 81 f150

Administrator

Don't see a picture, nor even a link to one.

But you can do the PMGR wiring as shown here: Documentation/Electrical/PMGR Starter Wiring. And the 3G as shown at Documentation/Electrical/3G Conversion, although there's two other pages below that which might help.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Shankles McBullnose

Re: Wiring questions with upgrades 81 f150

Would probably help to add the photo I'm talking about.

81 F150 460/C6 600 cfm Holley

Gary Lewis

Re: Wiring questions with upgrades 81 f150

Administrator

I don't know how to answer the question because I don't know what you've done.

Maybe we can take this one step at a time. Have you read the PMGR wiring page linked to above? Did you wire it the way shown? If so, nothing changes relative to the ignition on the starter re-wire.

On the 3G you'll see that there is a LG/R wire, NOT a R/G wire, that goes to the "I" terminal on the alternator. That wire is necessary for the alternator to be bootstrapped in, and w/o it the alternator will not work.

Gary, AKA "Gary fellow": Profile

Shankles McBullnose

Re: Wiring questions with upgrades 81 f150

I have wired the pgmr and the alternator is connected to that ignition wire. Does the "I" terminal on the relay stay empty?

81 F150 460/C6 600 cfm Holley

Gary Lewis

Re: Wiring questions with upgrades 81 f150

Administrator

If there wasn't anything on the I terminal on the starter relay then there shouldn't be anything on it after the wiring changes.

Gary, AKA "Gary fellow": Profile

Shankles McBullnose

Re: Wiring questions with upgrades 81 f150

One other question for the alternator. I've seen the a terminal connects to the b+ post, so the yellow wire is connected back to the alternator. I've also seen where that yellow wire goes directly to the a post on the relay. Any reason behind that?

81 F150 460/C6 600 cfm Holley

Gary Lewis

Re: Wiring questions with upgrades 81 f150

Administrator

It is easier to go back to the always-hot post of the starter relay than to the battery since the stud on the starter relay is long. And since the battery cable to the starter relay is much larger than the charge cable from the alternator, the two spots are electrically the same. So I always connect to the starter relay.

Gary, AKA "Gary fellow": Profile

Shankles McBullnose

Re: Wiring questions with upgrades 81 f150

Do these two behave any differently?

81 F150 460/C6 600 cfm Holley

Gary Lewis

Re: Wiring questions with upgrades 81 f150

Administrator

Here's a screen grab from our directions from the link given above:

Your first diagram puts the Y/W wire back to the alternator, which is correct. But your second one puts that wire to the starter relay side of the fuse, which is a bad idea. The reason for that is because if you blow that fuse then the alternator isn't seeing its own output and the voltage can go very high, potentially hurting the alternator.

So, why aren't you using our page on the 3G wiring?

Gary, AKA "Gary fellow": Profile

Shankles McBullnose

Re: Wiring questions with upgrades 81 f150

I am I just like to understand what and why something is the way it is

81 F150 460/C6 600 cfm Holley

Gary Lewis

Re: Wiring questions with upgrades 81 f150

Administrator

I, too, like to know why. And there are reasons we chose to wire it the way shown, like the possibility of blowing that fuse - and then blowing up the alternator.

By the way, do you have an ammeter? Did you take it out of the circuit?

Gary, AKA "Gary fellow": Profile

Shankles McBullnose

Re: Wiring questions with upgrades 81 f150

I was just looking and the digital gauge cluster I got from intellitronix has a voltmeter that just pulls the voltage from the board itself so it has no hook up for an ammeter. I'll probably get an aftermarket one later. I'm not even ready to hook up the panel yet

81 F150 460/C6 600 cfm Holley