1G Alternator Harness Question

[Jesse3877]

Hello, i believe a have a factory 1G harness and my truck probably came with a 40 amp alternator. I am interested in installing a tuff stuff 70 amp 1G alternator. I don't really need more amps but would like a new flashy alt with better idle output. My electrical requirements are just as basic as it was 40 years ago. Non A/C cab and i rarely use wipers or heat. I see that there was a harness for the 40 & 60 amp alternators and another for 70 amp alternators. Im guessing this is the case based on two different size fusible links (14g & 16g).

My question is if i had the 40/60 amp harness is it worth my time to install larger primary wire(10g) and larger fusible link to match? My next question is i see two splice points. one side closer to alternator and one closer to solenoid. the one splice at solenoid makes sense to be a fusible link (J?) but not sure about the one closer to alternator. Is this a link or just a splice point that has a weatherproof boot?
P.S. im struggle to make my pics right side up!

[Gary Lewis]

Jesse - Before we get into details, I'd appreciate it if you'd follow the directions given in the email you received, which said "Please go to the New Members Start Here folder, read the guidelines, and then start a new thread/topic in that folder about yourself and your truck."

All members are held to those guidelines.  So we ask everyone that comes in to go there, read the guidelines, and then post an introduction in that folder.  We cannot force you to read them, but at least having been on the same page as the guidelines there's a reasonable chance that you will.  And we've banned members who wouldn't adhere to the guidelines, and we don't want that to happen to you.

Now for the questions.  If the new alternator is only capable of generating 70 amps then you don't need to make any changes.  The shunt is sized to handle up to 70 amps, so you should be good to go.  And I don't see a need to change any of the fuse links.  If you aren't adding anything in the truck that pulls more current, then there's no need to change the wiring supplying that current to the truck.

As for the pics, check out the info here: Bullnose Forum/Forum FAQ's. Basically the issue is that the forum's software, like most forum software, isn't smart enough to read the orientation info your camera put in the metadata in the file.  So you need to open the pic in editing software and then save it.  The editing software usually reads the metadata and orients the file properly.  So if you then save it the orientation is usually correct.

[Jesse3877]

Hi Gary, thanks for your response. Makes sense and I’ll keep existing harness. I’ll make another post that introduces my myself and truck. I spent some time going through the FAQ’s trying to learn how to interface with the forum and still trying to understand some of the settings. It appears my pic and signature also got reset. Have a good night and thanks again.

[Gary Lewis]

Jesse - We are pretty laid back on things, except for the step of getting you to the New Members Start Here folder.  That's a key, as previously said.

Anyway, you'll fit right in.  Glad you are here.

[kramttocs]

Jesse3877 wrote

I’ll make another post that introduces my myself and truck.

Welcome! Looking forward to this upcoming post as even in just the two photos it looks like some cleanup and mods were done. Interested in seeing what all you have going on.

[FuzzFace2]

I wonder if the plugs could be different between the different AMP ALT's?

I say this because the 2 trucks - both 81's with 300 six (1 AC 1 not) had different plugs on the ALT between them.
Now I don't know if the ALT I had was the right one for the truck or not, it had wires replaced in place of the harness.
Where the harness I used from my parts truck would not plug into the ALT and I did not have the ALY to match the harness.
Dave ----

[ArdWrknTrk]

Dave, there are two different alternator-regulator wiring schemes but I've always thought it had to do with ammeter or not.

Perhaps I was mistaken, and it is down to whether the truck had AC or not?

[Gary Lewis]

I can't tell you the differences, but there were 18 different alternator to voltage regulator wiring harnesses.  

Source: Documentation/Electrical/Wiring Harnesses.  (Yep, I added that harness.)

[FuzzFace2]

ArdWrknTrk wrote

Dave, there are two different alternator-regulator wiring schemes but I've always thought it had to do with ammeter or not.

Perhaps I was mistaken, and it is down to whether the truck had AC or not?

I guess it could be either or?
Being I did not have the ALT from the parts truck, only the wiring harness and only had the ALT from my truck but no harness (someone took wire and crimped ends on and then to the ALT.

So for all I know that could be the wrong ALT? Being I did not have the right plug for the ALT and did not want to cut the plug off the harness I took 2 short wires and crimped ends on to make an adaptor of sorts.
This way if the ALT fails I can hit the parts store for a replacement that will be P&P.
Then again I may then go for the 3G ALT?

BTW the only time I see the head lights dim a little at idle is when I first start the truck and back out of the garage, heater fan on low & radio is on also.
I let it idle while the garage door is closing before driving off. 1/4mile down the road and stop for the light I don't see them dim then it is on the high way for 30+ miles.
I can live with that.
Dave ----

[ArdWrknTrk]

Relay Harness makes a HUGE difference!  👍

[FuzzFace2]

ArdWrknTrk wrote

Relay Harness makes a HUGE difference!  👍

And I have it installed and it still dims at idle but only when I first start it.
It hardly spins before the motor starts, but just that little it pulls power from the (new) battery.
I think because the ALT is not spinning fast enough and the battery just got power pulled from it is why it happens?
Again with in 2 miles I am on the high way for 30+ miles so the battery has time to recharge and I don't see it happening after that.
Dave ----

[Gary Lewis]

Yes, that's surely why the lights dim just after starting.  The battery voltage is down a bit and the regulator is calling for that it to be topped up.  But the alternator's output isn't much at idle, so the voltage stays down enough to notice in the lights.  

[Jesse3877]

Thanks for the editing software tip. Was able to correct the orientation by editing the picture on my iPad. I added a couple blue arrows. Good to know for future reference mainly because I would be adding pics from iPhone or iPad normally and not from computer. Cheers

[Gary Lewis]

Good job, Jesse!

[Rembrant]

Jesse3877 wrote

Jesse, you need a new battery tray! I had to replace mine a couple years ago...what a terrible design they were, with the tray mounted UNDER the fender liner. Those things rusted and fell apart here so fast I've never seen one still intact to this day. Anyway...they are available as are the hold down rods and top brackets, etc.

[ArdWrknTrk]

You can upgrade to the stay supported Bricknose battery tray as well.

These mount atop the fender liner, handle a group 65-2 battery and use a wedge type 'shoe' for a hold down.

[Rembrant]

ArdWrknTrk wrote

You can upgrade to the stay supported Bricknose battery tray as well.

Oh, I didn't know that when I replaced mine. With my truck being a summer cruiser now, the battery tray will last forever, but hanging down there in the salt the originals didn't last very long.

[ArdWrknTrk]

I'm fairly certain that this was covered when Gary was considering how to deal with dual batteries in Big Blue.

[Gary Lewis]

Yes, we did discuss it.  And I posted a pic not long ago.  But I'll be covering it in more detail when I do it - hopefully soon.

The later one does look like it'll come too close to the starter relay for my comfort, so I expect to have to relo the relay slightly.  Or, replace it with a Bosch-style relay since I'm using a PMGR starter.

[ArdWrknTrk]

I wonder how different the relay locations are between the two generations?
My battery tray was comfortably away from my starter relay (when I had one)