84 Bronco 3g alternator upgrade problem

[StraightSix]

Hi everybody. Im working on a 3G alternator upgrade for my 300 – 6 1984 bronco. So far, I have purchased the alternator, removed the stock 1G and have completed most of the wiring. I ran into something that I haven’t seen mentioned in any of the documentation on this site or elsewhere. When I removed the old alternator harness the wires were removed from the back of the original alternator, the external regulator was removed from the engine bay wall near the battery, and then I had to unhook a 4 blade electrical connector that goes into the trucks harness. I didn’t know about that 4 blade connector. One of the 4 wires in/out of that connector seems to be the “red/green” wire that goes to the “I” terminal of my 3G alternator. After reading around on this forum and some others, I now believe that two of the three remaining wires go to my ammeter and the fourth (the big yellow one) supplies power to the headlights and some other stuff too though Im not crystal clear on what. Here is a picture of the onnector in question.

 

 

Here are some diagrams that I took from another post on the bullnose forum. This drawing omits the alternator regulator wiring. This one seems to show my trucks wiring in more or less factory configuration. I Assume that the 4 prong connector is shown in this diagram as “C610”.

 

 

Assuming that Im correct about C610, this picture shows what I currently have with the charge wire in red and the other wires in black. This is the current state of my Bronco

 

 

Finally, If I understand correctly, this is what I think I need to do to get my bronco running. This would leave the ammeter nonfunctional. I have already ordered the voltmeter from rocketman.

 

 

Do I have it all right? Am I missing anything? Do I need a resistor in line with the red and green wire? If I have it all right, my plan would be to cut the male end of that connector out of the old regulator harness, clip it back into the female end, splice my red/green wire from the alternator to the red green wire on the male end of the plug, and then crim on a ring terminal to the big yellow wire and put that on the battery terminal of my starter solenoid to provide power to the headlights. Probably wire nut the two wires from the ammeter together, as they shouldnt be hot anymore, right? Any help would be greatly appreciated. Please let me know if my question is unclear or if I have left out any important information. Thanks!

 

[Gary Lewis]

Yes, that's surely C610. And, you've asked some good questions. Unfortunately our page at Documentation/Electrical/3G Conversion needs some upgrades as we don't have one schematic that answers all the questions.

So, instead of answering your questions and then having to suggest other alternatives, let's go straight to the diagram below from that page and then the Ammeter & Voltmeter tab. This shows how I suggest you wire the output from the alternator. And what it says is:

• Take the output to the starter relay, but I really recommend that you put a megafuse in that circuit, probably w/a 150 amp fuse in it.

• Leave C610 and the shunt in place. Yes, you'll have a tiny voltage drop across the shunt, but it won't be enough to notice.

• Cut the yellow/light green wire on the cab side of C610, not on the engine side as shown below, and take that to ground via a relay closed by a key-on signal. Otherwise your voltmeter will be registering 24x7 and you'll slowly drain your battery.

Then this drawing shows how to wire the rest, which you seem to have figured out. But you must have some switched power on the red/light green wire to bootstrap the alternator. However, you don't need a resistor nor bulb, just tie the existing red/light green wire to the alternator's "I" input.

Does that answer all of the questions?

[StraightSix]

Yes, that's surely C610. And, you've asked some good questions. Unfortunately our page at Documentation/Electrical/3G Conversion needs some upgrades as we don't have one schematic that answers all the questions.

So, instead of answering your questions and then having to suggest other alternatives, let's go straight to the diagram below from that page and then the Ammeter & Voltmeter tab. This shows how I suggest you wire the output from the alternator. And what it says is:

• Take the output to the starter relay, but I really recommend that you put a megafuse in that circuit, probably w/a 150 amp fuse in it.

• Leave C610 and the shunt in place. Yes, you'll have a tiny voltage drop across the shunt, but it won't be enough to notice.

• Cut the yellow/light green wire on the cab side of C610, not on the engine side as shown below, and take that to ground via a relay closed by a key-on signal. Otherwise your voltmeter will be registering 24x7 and you'll slowly drain your battery.

Then this drawing shows how to wire the rest, which you seem to have figured out. But you must have some switched power on the red/light green wire to bootstrap the alternator. However, you don't need a resistor nor bulb, just tie the existing red/light green wire to the alternator's "I" input.

Does that answer all of the questions?

Gary,

Thanks again for another extremely helpful post. My charging wire is a size 4 with an inline 175A fuse, and it lands on the battery terminal of the starter solenoid. My A wire is terminated on the alternator side of the 175A fuse instead of dirrectly onto the alternators output terminal simply because I had the right ring terminals to do that cleanly.

As I understand it, I should plug C610 back in. The red and green wire needs to be joined with the red and green wire from my alternator on the engine side of C610. The yellow/green ammeter wire needs to be grounded so it can serve as the ground of my new volt meter, but this needs to be accomplished through a key on relay so it doesnt drain the battery.

Where do I need to cut/dissasemble the old alternator harness? This is what it looks like now. My finger is pointing to the male end of C610.

What happens to the red ammeter wire? Im just unsure of how to incorporate the parts of the old harness that I still need. Thanks again!

Ps- the voltmeter wont arrive for a good little while. Can I drive the vehicle without it, so long as I dont have loose 12V wires hanging around grounding out on stuff? I was considering getting one of the cigarette lighter volt meters so I have something to look at until the real gauge arrives. Would that be a mistake?

[StraightSix]

Gary,

Thanks again for another extremely helpful post. My charging wire is a size 4 with an inline 175A fuse, and it lands on the battery terminal of the starter solenoid. My A wire is terminated on the alternator side of the 175A fuse instead of dirrectly onto the alternators output terminal simply because I had the right ring terminals to do that cleanly.

As I understand it, I should plug C610 back in. The red and green wire needs to be joined with the red and green wire from my alternator on the engine side of C610. The yellow/green ammeter wire needs to be grounded so it can serve as the ground of my new volt meter, but this needs to be accomplished through a key on relay so it doesnt drain the battery.

Where do I need to cut/dissasemble the old alternator harness? This is what it looks like now. My finger is pointing to the male end of C610.

What happens to the red ammeter wire? Im just unsure of how to incorporate the parts of the old harness that I still need. Thanks again!

Ps- the voltmeter wont arrive for a good little while. Can I drive the vehicle without it, so long as I dont have loose 12V wires hanging around grounding out on stuff? I was considering getting one of the cigarette lighter volt meters so I have something to look at until the real gauge arrives. Would that be a mistake?

Now I see that the red wire, through the harness, still ends up landing on the starter solenoid battery lug, thus acting as my volt meter hot wire.

[Gary Lewis]

Gary,

Thanks again for another extremely helpful post. My charging wire is a size 4 with an inline 175A fuse, and it lands on the battery terminal of the starter solenoid. My A wire is terminated on the alternator side of the 175A fuse instead of dirrectly onto the alternators output terminal simply because I had the right ring terminals to do that cleanly.

As I understand it, I should plug C610 back in. The red and green wire needs to be joined with the red and green wire from my alternator on the engine side of C610. The yellow/green ammeter wire needs to be grounded so it can serve as the ground of my new volt meter, but this needs to be accomplished through a key on relay so it doesnt drain the battery.

Where do I need to cut/dissasemble the old alternator harness? This is what it looks like now. My finger is pointing to the male end of C610.

What happens to the red ammeter wire? Im just unsure of how to incorporate the parts of the old harness that I still need. Thanks again!

Ps- the voltmeter wont arrive for a good little while. Can I drive the vehicle without it, so long as I dont have loose 12V wires hanging around grounding out on stuff? I was considering getting one of the cigarette lighter volt meters so I have something to look at until the real gauge arrives. Would that be a mistake?

Yes on C610 and the red/light green wire. And probably yes on the yellow/green wire, but you want to ground the wire coming from the cab, meaning the one coming from the voltmeter. It'll be the one in the harness still on your truck.

On the harness you are pointing to, here's what you should do with the wires from C610:

• Red/Orange: This is the wire that goes to Splice 203 and then through Fuse link J to the starter relay. You need to keep it.

• Yellow: This is the large wire that connects to Splice 202 and you need it.

• Yellow/Light Green: As said, you won't use this so can cut it and put a piece of heat shrink on it.

• Light Green/Red: As discussed, this goes to the alternator's LG/R wire

Beyond that, you don't need the rest of the regulator's wiring harness. More specifically:

• Yellow/White Dots: Cut this wire off at Splice 203

• Black/Orange: Cut this wire off at Splice 202

Does that answer the questions?

 

[Gary Lewis]

Now I see that the red wire, through the harness, still ends up landing on the starter solenoid battery lug, thus acting as my volt meter hot wire.

Yep.

[StraightSix]

Now I see that the red wire, through the harness, still ends up landing on the starter solenoid battery lug, thus acting as my volt meter hot wire.

Yep.

I think that answers most of my questions, Ill have to get the harness into my hands and look it over. Ill just need to carefully label all of the splices wires and links before I start cutting. Ill do my best to take detailed photos so that others can use it to follow along in the future. Thanks again! I should have a follow up post tonight.

As a matter of interest, I am using a duralast alternator part number DL7734-6-11 which is a reman motorcraft with a lifetime warranty. The thichness of the ears seems to be a perfect match to my 1g alternator, no bracket modifications seem to be necessary.

Also, for the shim between the alternator and the v belt pulley you might get away with using an M18 ring shim from mcmaster carr in 1.0mm thickness (.039") or a 1.5mm thickness (.059"). They are inexpensive and would be an easy way for someone who doesnt have access to machining tools to get the shim they need. I am not positive that the inside diameter would be suitable though. Ill be using a shim that a buddy with a lathe is going to turn for me

[StraightSix]

I think that answers most of my questions, Ill have to get the harness into my hands and look it over. Ill just need to carefully label all of the splices wires and links before I start cutting. Ill do my best to take detailed photos so that others can use it to follow along in the future. Thanks again! I should have a follow up post tonight.

As a matter of interest, I am using a duralast alternator part number DL7734-6-11 which is a reman motorcraft with a lifetime warranty. The thichness of the ears seems to be a perfect match to my 1g alternator, no bracket modifications seem to be necessary.

Also, for the shim between the alternator and the v belt pulley you might get away with using an M18 ring shim from mcmaster carr in 1.0mm thickness (.039") or a 1.5mm thickness (.059"). They are inexpensive and would be an easy way for someone who doesnt have access to machining tools to get the shim they need. I am not positive that the inside diameter would be suitable though. Ill be using a shim that a buddy with a lathe is going to turn for me

Gary,

I followed your directions and it was quick and easy. Thanks again!

Here is what I started with

I cut the red and green wire as close to the old external voltage regulator as possible. I then cut the small yellow wire running from the old voltage regulator to fusible link 203 as close as I could to fusible link 203. Then, I cut the old charging cable away from the 4 way intersection S202 as close as possible, as well as the small diameter yellow wire. Now it looks like this.

From here, I electrical tape wrapped the exposed conductors then slid the excess length of the heavy back and yellow wires down into a peice of 3/4 shrink tube to encase those wires, keep everything tidy, and reduce the chances of a short. The small green and red wire goes to the alternator and the small yellow and green gets grounded through a relay and becomes the ground for the volt meter. The ring terminal goes to the starter solenoid hot terminal.

Does that all sound right? Thanks again Gary!

 

[Gary Lewis]

Gary,

I followed your directions and it was quick and easy. Thanks again!

Here is what I started with

I cut the red and green wire as close to the old external voltage regulator as possible. I then cut the small yellow wire running from the old voltage regulator to fusible link 203 as close as I could to fusible link 203. Then, I cut the old charging cable away from the 4 way intersection S202 as close as possible, as well as the small diameter yellow wire. Now it looks like this.

From here, I electrical tape wrapped the exposed conductors then slid the excess length of the heavy back and yellow wires down into a peice of 3/4 shrink tube to encase those wires, keep everything tidy, and reduce the chances of a short. The small green and red wire goes to the alternator and the small yellow and green gets grounded through a relay and becomes the ground for the volt meter. The ring terminal goes to the starter solenoid hot terminal.

Does that all sound right? Thanks again Gary!

Yes, I think you are right. Well done!

[StraightSix]

Yes, I think you are right. Well done!

Thanks a ton Gary! Ill be sure to update you when I actually get it running which will probably be Monday or Tuesday. Now Im working on figuring out how I want to wire the winch in. Its more an issue of routing those big cables than anything else. There arent a lot of convenient spots to put them, and I want it all to be pretty easy to remove since the winch will only be on the vehicle when Im going somewhere it could be useful.