3 Wire Alternator Hookup Explained- It's Easy- If I Can Do It, So Can You! Bad Hombre Garage Ep. 88

In this episode I replace the old externally regulated and unreliable 12 volt GM alternator with a remanufactured Delco 10si GM alternator. There were some differences in wiring, so I took a few minutes to explain how to connect the alternator, from charging to exciting to regulating. I also replaced my ammeter with a voltmeter for simplicity sake. All the work is done on my 1964 early CJ5, Willys Jeep with the F-134 engine. It was converted to a GM style 12 volt alternator way back in the day, and finally needed an upgrade. The wiring I explain is fairly universal, from an old Jeep like this to a muscle car or hot rod with the standard three wire alternator. I also talk about what the exciter wire and idiot light do. Thanks for watching, please leave a comment and let me know what you think.
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[@DiscoBallGaming]

I have NEVER been more happy to see a CJ5, I have one just like this and have never been able to find anything online about wiring until I found This video. You are a GODESND and I'm glad I found this, thanks

[@BadHombreGarage]

Right on! I’m glad you find it useful. I have a few more videos of me struggling to keep the old Jeep on the road if you want to explore my channel a little bit. Thanks for watching and taking the time to comment.

[@HirschCustoms]

I have a 73 jeep gladiator with a amp meter that Is no longer hooked up. Yes thats how they are wired... caught fire after I did a timing job. Had to buy a new amp meter, rip it apart and use the old meter parts to build a new one... worked great can't tell but go figure it's the only gauge I couldn't buy and replace. Found a way out. I watched the video to find out how to wire my alternator for charging my RV batteries thats driven by my waste oil diesel engine. So thanks for the info.

[@BadHombreGarage]

Thanks for watching and taking the time to comment!

[@js1936mac]

Thank you ,good Job on the volt meter, nessesity is the mother invention. That's a great jeep!

[@BadHombreGarage]

Thanks for watching!

[@MsBugativeyron]

Thanks for answering my question on the bulb fitted at the alternator 👍

[@BadHombreGarage]

I hope it helped!

[@ranchosendero]

Thanks for the great simplified explanation...tons of help!

[@BadHombreGarage]

Thanks for watching!

[@richardharrold4357]

Alternators are something else. Trying to to learn the things. My tractor exciter is not working and driving me crazy. I have a work around but sure would like the dang thing to work as designed. Thanks for you video.

[@BadHombreGarage]

Good luck! Thanks for watching and commenting.

[@rustyrods8535]

You covered the charging change very well and will not doubt solved someones charging issues . I’ve used a one wire on all my builds , my builds are mostly ford but you can get the Chevy one wire alternator with a Ford case ...makes my life much more simple . Thanks for sharing ..Shawn

[@BadHombreGarage]

Thanks! I have a one wire on my Model A, it is really easy. I wanted a one wire for my Jeep, but it was a 3 wire that showed up so I just used it.

[@johndowe7003]

You got a part number for a ford alt with one wire?

[@rustyrods8535]

@@johndowe7003 yes sir Summit Racing , tuff stuff part number 7068 , NAPA has the same alternator also but I don’t know that part number .

[@BadHombreGarage]

@@rustyrods8535 thanks for helping out! I love this community.

[@DamionStLouis]

Finally a good explanation of this! Ty

[@BadHombreGarage]

Thanks for watching and for commenting!

[@DesertRatFabrication]

Good fix, it's nice to get away from the external regulator makes life so much simpler, looks like you are getting so nice weather

[@BadHombreGarage]

Yep, so much easier. The weather has been beautiful here, high 50s and maybe 60 today. There’s more snow forecast for later this week though.

[@patriotpat2228]

Many of the new 1 wire alternators can also be used as a 3 wire. They are sort of a universal type of upgrade for when you are just looking for more amps.

[@BadHombreGarage]

Good info, thanks.

[@diyfamily6848]

Incorect you need to definately only use a 2 watt bulb between ignition hot and IND terminal. Yes this is the initial exitation wire and requires the 2 watt light bulb for(1) indicating the alternator is charging, and (2) to limit the current on this wire during initial magnetizing of the rotor. No you cannot use an LED for this because it is a Diode and also it will not allow enough current to exite the field.

[@BadHombreGarage]

Thanks for your knowledge!

[@larsonarchitecture]

Super helpful! Thank you

[@BadHombreGarage]

Right on! Glad you find it helpful!

[@markvanfossen7931]

Thanks for the video, it was just what I needed getting my old tractor wiring correct. I researched the LED idea and even though it is a diode, it takes other components to work correctly so why bother.

[@BadHombreGarage]

Good call, thanks for the inputs!

[@noccis3448]

Good vid!

[@BadHombreGarage]

Thanks!

[@dennybaker8755]

Been watching so many of these videos and all people do is waffle on forever --- may as well touch all the wires together until some thing works .

[@BadHombreGarage]

Give it a rip, let us all know how it works out.

[@RGGarage]

Good video. Going to need to do this on my 53 Chevy truck. 👍

[@BadHombreGarage]

Right on! Thanks for the compliment!

[@RealJohnnySharp]

I’m converting an old tractor to 12v and replacing the generator with an alternator. I think I understand most of this and have started an updated wiring diagram, the only one I’m not sure about is the “2”/“F” connection for mine. The “1”/“R” I believe is the exciter wire you mention and I have it tracing back to the key switch (don’t have a dummy light or anything in there yet but will add one). The main post from alternator I have going to ammeter, with other side of ammeter going to battery post on starter solenoid. The tractor does have lights so I’m trying to figure where the “2”/“F” connection should go.

[@BadHombreGarage]

If I’m not mistaken, the F would be hot when the key is on.

[@RealJohnnySharp]

So if the F goes to the key switch, where would R go? I thought the exciter wire was the R and was what went to the key switch. I must not have understood correctly from the video.

[@BadHombreGarage]

@@RealJohnnySharp no, you understood correctly. I was wrong in my first response to you. I would set it up like you suggest. 1/R as exciter. Sorry for the confusion.

[@td42dirtygq]

Good video keep it up 👍🏾 I just have one question on the alternator do you have to connect a negative wiring to the battery or engine or body of car thanks

[@BadHombreGarage]

It pulls a ground through the mounting brackets, though I have seen some with a ground wire off the body of the alternator. If in doubt, I say make sure it is grounded! So many problems come up due to poor grounds. I always make sure the battery is well grounded to the frame, then make sure the body and the engine are also grounded to the frame.

[@opinion4246]

Thanks good help

[@BadHombreGarage]

Thanks! I’m glad it was helpful.

[@rockvillemike6062]

The "exciter" wire supply current to the alternator to get it started generating. When it gets going it doesn't lose it's ground but the alternator supplys current out of itself thru this wire. Then you have voltage feeding into the idiot light from both ends so no current can flow and the light stops glowing.

[@BadHombreGarage]

That’s a great explanation, thanks!

[@notsofast5495]

What about fuses. I have an old Jeep like this with a 3 wire GM alternator. I have my hot from alternator going directly to my battery. I have HOT from solenoid going to a junction block under the hood then to BATT on ignition switch. I have exciter wire from alternator going to IGN on fuse block under dash then to IGN on ignition switch. I’m getting my wipers, blower, fuel pump power from the IGN portion of junction block and the lights from POS portion on the junction block. I have each accessory with its own fuse but I’m not sure if I need a fuse in the charging system

[@dipndalip]

Thank you very much

[@BadHombreGarage]

Thanks for watching and for taking the time to comment!

[@bethells86]

Great, I was wondering what numbers 1 and 2 mapped to.

[@BadHombreGarage]

Glad it helped!

[@briizcustoms9543]

What are those green wires for? On my 1976 Chevy p20 the green wire is burned off at the end. Also noticed my gages all spin now after I got a new alternator. Any advice!???

[@BadHombreGarage]

That's a good question. I'd look into why that wire burned... it may be going to ground somewhere. Speaking of grounds- your gauges may be acting goofy because of a poor ground. Always make sure there are good grounds from the unit to ground, from the cab of the vehicle to the frame, from the engine to the frame, and from the frame to the cab.

[@angelobryan4699]

Or use a diode in series with the excitation terminal

[@BadHombreGarage]

👍

[@stepsvideos]

Many thanks. I was asked to fix the alternator wiring, and hunt down a battery drain. The owner had the 2 pin connector plugged in backwards. Fixed that, but then the engine kept running after key off, and the sense wire was getting hot. Oops, did I just fry the alternator? Nope, turned out the owner had shortened the sense wire, which was a resistance wire. It was reading 3ohms, instead of 15. It's a bit of a flaky design, counting on a resistor wire to shut off the engine. I'm considering putting in a relay, to break that connection on igmition off. By the way, did you happen to take a resistance measurement from pin2, sense wire tab on the alternator, to ground (connector unplugged)? I measured about 14k. It's not much, but it does result in a battery drain of about a milliamp. Could that be a sign that the alternator regulator is about to go out?

[@BadHombreGarage]

I did not take any resistance readings, and I not sure what it should read. Hopefully someone can add some info here in the comments? Sounds like you are a good troubleshooter! Thanks for watching.

[@CarAudioEnthusiasts]

on gm alts you can use a 470ohm 1/2 watt resistor in place of a bulb

[@guylipsky3599]

I picked a 51 chevy and it has a Painless Wiring, problem I have is the alternator is drawing 2 amp , and this is the new alternator the old one was drawing 3.3 amp on the negative post and I am not sure what to do , if I leave the truck on a trikle charge it's fine but it's not correct

[@BadHombreGarage]

Definitely something drawing on your battery. Maybe the alternator exciter wire is constant hot instead of keyed power?

[@dbc105]

If I understand this correctly, my 1990 Dodge D150 has the regulator inside the ECM(yep called ECM in 1990) and my voltage is about 13.5. At 66yrs old I've owned a lot of cars and what was always common was about 14.4v. I just got thos old pickup so it may be a non-issue but I'm thinking if it has trouble keeping the battery up I can just add a little resistance to the signal field wire to fool the system to increace output voltage a little. I know on my Roadrunner I moved that wire from the connection on the cowl to under the dash when the headlights pull power and my dim headlights were solved. Have you done this before and know what might be a good resistance to use? Thanks, good video.

[@BadHombreGarage]

I like the way you think. I haven't done that before, but I think it could work. That said, I have no idea what resistance would work for you. I think, if that was my project, I might just pull an output from this side of the ECM (where the low voltage is) and use that to feed my signal to the alternator. All that said, I bet 13.5 volts will be good enough. Thanks for watching and taking the time to comment!

[@dbc105]

@@BadHombreGarage Thanks for the reply. I'm going to watch and see how it does, I may be expecting an issue that never comes, I'm just trying to think ahead in case. If I change anything I'll let you know.

[@BadHombreGarage]

@@dbc105 👍

[@StevenPenny]

I don’t have anything connected to 1 or 2, will that be an issue? I’m getting 14.1v in my battery box. What stops it from charging the batteries too much? Like if you went on a 24hr ride, wouldn’t the alternator sending 14v to the batteries harm them?

[@BadHombreGarage]

You might have a true one-wire alternator if the 1 & 2 posts do not have wires and it still excites and charges. An alternator should put out between 13.5 and 14.5 volts (on a 12v system) in order to charge the 12v battery, so no I don’t think it will cause any harm.

[@russellmanweller6694]

If the stator and fase are both supposed to go to the external voltage regulator, but the stator wire goes to a harness with a bunch of wires and ties into the cars electrical circuits instead of going to the external voltage regulator like all the videos show, then what do you do. My new high output alternator is designed to charge normally with zero other connections other than to the battery, but I can jump the wires on the harness for the external voltage regulator like every video shows because my stator wire never went to it. I have a stator wire coming from my dashboard and have no idea what to do with it. It's a 1977 ford Econoline club wagon.

[@BadHombreGarage]

Hmm, I’m not sure what to make of that either. Calling all the other viewers! Anyone have thoughts on this?

[@jameslangford4748]

My problem is that I have a mess of wires under the dash, no proper harness. I don't know where to connect the exciter wire from my regulator. I have the small light and the proper gauge wire. Do I trace the wire back from my coil (positive side) to my ignition and connect there ? Don't I have to ground the bulb. I know you can't nuse an LED. Please help?

[@BadHombreGarage]

Were you able to sort this issue out?

[@rosemcbirney5123]

My exciter light only goes out when I rev the motor higher say 1500 rpm then it drops back to idle and it stays off what do you think I have to do to fix

[@BadHombreGarage]

I think that makes sense and is actually working correctly. An alternator needs to get up to a certain RPM (usually the engine around 1200) before it starts charging, then it will continue to charge even though it drops below that. Your light is just showing you that the alternator isn't charging yet. Of course, this means that you'll want to blip the engine on startup just enough to get that light to go out so that you're not discharging the battery as the car warms up.

[@rayfabris2512]

do you know the order of the 3 wires that go into the plug on the alternator? the wire came out of the plug so I got a pigtail repair kit I just don't know the order if you can help me I would appreciate it thanks

[@BadHombreGarage]

I'm not sure the order... there should be one bigger wire that goes on the back of the alternator, then two that go into the plug. you have a 3 wire plug?

[@ryanlamanna9761]

If I wired the exciter wire to the + side of the coil with a diode in-line would that have the same effect as running the light bulb?

[@BadHombreGarage]

I guess that might work… but it might be easier to hook it up to a hot wire elsewhere.

[@ryanlamanna9761]

@@BadHombreGarage so I could hook up to the positive side of the coil? As long as I have an Inline Bulb or diode?

[@alonsoburquez6971]

So if I Connect the wier to the coil that’s the Distributor right and it will still charge my battery on my car

[@BadHombreGarage]

Depends on which wire you connect. The big wire that is on the single output post of the alternator should go to the battery, but I think a guy could connect the excite wire to the coil and it would function.

[@jayreed2885]

Does any light bulb from any head light off of a crash car work.

[@BadHombreGarage]

I would imagine so.

[@eliboss1080]

Can I run the “exciter” wire on the alternator to a auxiliary switch to activate the alternator?

[@BadHombreGarage]

Yes!

[@INTERNA9]

Thanx

[@BadHombreGarage]

You bet!

[@twalatka]

Can you please tell me why they hooked the negative lead from my battery to the alternator? And where is my positive wire supposed to go? My battery is NOT charging!!!

[@BadHombreGarage]

That’s a strange one… I have not heard of it before. What kind of vehicle? On a negative ground system (which the one in the video is) you could expect the negative lead to connect to the frame of the vehicle, and that the engine and body would also be grounded to the frame. The positive would need to be connected to the alternator, or to a wire being powered by the alternator in order to charge the battery.

[@twalatka]

@@BadHombreGarage 71 Chevelle.

[@twalatka]

@@BadHombreGarage thanks for getting bach to me

[@BadHombreGarage]

@@twalatka that should be pretty straightforward, I think. See where the wire off the main post of the alternator goes. You might have to chase it around a little, but it should go back under the dash or to a relay where it will provide main power to the car. Then chase where your positive lead from the battery goes… probably to the big post on the starter. If those wires are in the right place, and everything is grounded properly, it should work.

[@twalatka]

@@BadHombreGarage Thanks, there are strange wires going behind my battery, one going over my radiator and down towards the passenger headlight. I'm going to have to do a lot of chasing. Thanks.

[@robertapperson3710]

Dood you know what your talin about,but just asked a simple ? Wasn't asking for the whole wiring system how that works. Just 3 wire alternator! I was going to explain my thoughts to but nobody gaf! Thanks !

[@BadHombreGarage]

Ha, ok thanks.

[@mwinscott7858]

Drawing picture needed....

[@BadHombreGarage]

That’s a good idea!

[@justenkelley7158]

Isnt there a way to use some sort of signal relay so you can separate out the high powered heavy gage wire side from the low power light gauge wiring to the amp gauge...

[@BadHombreGarage]

Sure, I guess you could run a relay to the gauge.

[@AnonymousAnonymous-dn2pk]

Is it possible to change the wiring without having to remove anything else besides the wiring? It’s like I want to do the job but I don’t want to have to take anything else off but just the wiring. 89 22RE Toyota

[@BadHombreGarage]

Probably; though I’m not sure why you don’t just want to use the Toyota alternator and wiring?

[@AnonymousAnonymous-dn2pk]

@@BadHombreGarage I do want to; however, currently my alternators keep dying after being on and running fine for a while and I just keep replacing the alternators. The wiring is very old and even frayed with exposed wires coming out every which way which makes me suspect the wiring is the cause of the problem. I suspect changing the wiring will fix the underlying problem and therefore solve the main issue.

[@BadHombreGarage]

@@AnonymousAnonymous-dn2pk yes, I agree the wiring might be the problem. It might be tedious, but worth repairing the frayed wires.

[@AnonymousAnonymous-dn2pk]

@@BadHombreGarage Do you think it would fix it if I just meticulously taped them?

[@BadHombreGarage]

@@AnonymousAnonymous-dn2pk it might, but you can’t go wrong by meticulously replacing the bad wires either.

[@joshuaverfurth2203]

Im having a hard time understanding anything about electric, and honestly it all makes sense when you say it, but then trying to use it and practice it is just baffling...

[@BadHombreGarage]

It can be challenging- I have to study things a lot and look at a lot of references before I understand electrical. Stick with it, you’ll figure it out. Thanks for watching!

[@pawpatina]

FUN FACT: If you are converting a 6v to a 12v system... you can use the original 6v genny just by changing the voltage regulator to a 12v version...

[@BadHombreGarage]

Boom- thanks for the knowledge drop! I didn’t know that, but it makes sense.

[@pawpatina]

@@BadHombreGarage Yessir, the genny puts out like 96v or something all the time hence the regulator... same as a 12v alternator but it "alternates" between charging and not charging as needed with an internal regulator.

[@rafaelmarquez3948]

One or two seconds of ugga duggas..... my type a guy

[@BadHombreGarage]

Haha! Thanks.

[@braleyshardwoodcustoms8584]

Does the key side hook to the r side or s side

[@BadHombreGarage]

I believe the r terminal.

[@julieverma5804]

2009 done journey altanator😊😊❤

[@BadHombreGarage]

👍

[@TurtleWaxed]

An LED would not work right to replace the bulb as it has too low OHMS when it is turned on. A resistor would be a better choice. Take a look at an alternator load harness made by using three 1K ohm resistors in parallel (330 Ohms).

[@BadHombreGarage]

Thank you for the inputs, hopefully someone looking for this info will find it here.

[@ogairbender808]

I've been working on a 93 cutlass supreme convertible and for some reason the excite wire doesn't work ,the alt will charge for a while and then stop charging,after three alts we realized that the alts we're not the problem ,had a shop wire a basic relay in line on the excite wire some how and it works so far but,I would like to know how this works or how it is wired to work any ideas?

[@JamesAutoDude]

There's also alternators that have R and L instead of the 1 and 2. I can't figure it out 😭

[@BadHombreGarage]

I believe L is for the warning light, R is the excite wire (like power from the ignition).

[@JamesAutoDude]

@@BadHombreGarage okay thanks. Sadly my wires are all jacked up so it's not even hooked up to anything

[@jeffreyking1745]

Power to solonoid?

[@BadHombreGarage]

Which solenoid? The starter solenoid gets its signal from the key switch.

[@1badombre82]

Nice channel name ahaha

[@BadHombreGarage]

Oh man, that’s awesome!

[@randallfranklin5372]

What State you located

[@BadHombreGarage]

Colorado

[@jakethetamalejohnson1673]

God I wish I was smart enough to understand this shit.

[@BadHombreGarage]

Ha! If I can figure it out anyone can. Just keep doing research and asking questions.

[@Richar602]

All this bloke wants to do is talk not show. He lost my limited attention just after the start.

[@BadHombreGarage]

@Clive Taylor: This bloke is chuffed over your feedback! Also, KZbin has a feature where you can click on the little time bar at the bottom of the video, then move ahead or back to view any point in the video. This will keep you from having to listen to some poor chatter box’s mindless blathering whilst getting cheesed off at him faffing around.

[@abelcortezvargas5594]

Great info thanks for this video

[@BadHombreGarage]

@@abelcortezvargas5594 thanks!