do yourself a favor and get a decent multimeter
Scool Me In Wiring (1 Viewer)
- Thread starter RWBeringer4x4
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do yourself a favor and get a decent multimeter
For gauges, speedo, etc. the best thread I've seen is Rudi's ( @bj40green ) thread - search for "Clusters, Gauges, Speedo"
- Thread starter
- #43
Putting this here for future cross-reference.
https://forum.ih8mud.com/threads/clusters-gauges-speedo-odo-meters.544543/
https://forum.ih8mud.com/threads/clusters-gauges-speedo-odo-meters.544543/
- Thread starter
- #44
I believe I have this one: http://www.harborfreight.com/7-function-multimeter-98025.html
May not be a "good" multimeter, but hopefully it will do the trick
we modified several of our multimeters (at least one of which is a HF unit) to have clamp ends, at least on one of the ends - leaves one hand free to wiggle things . . . 
- Thread starter
- #46
Alright, folks - I'm back, and I'm happy to report that while I'm very much a deer in the headlights when it comes to all this electrical crap, I've started to piece the puzzle together.
Things I've learned: I'm running an Autolite 7122 Alternator. Every store online selling one says it is externally regulated. What's weird is: It appears to be a "one wire" setup, as others have mentioned. HOWEVER - Apparently this truck used to run the traditional 3-wire setup - since the "mystery box" on the fender is a GM Voltage Regulator, and that unplugged wire labeled "ALT" runs back to the regulator. The regulator also taps into the battery by one of the two smaller red cables (at least it did, until I broke it
), and the last wire coming out of the regulator runs to the dash - so I'm assuming that's my ammeter connection.
Long story short, it appears that I'm running the remnants of 2 different GM Alternator setups. Sounds like the initial 3-wire one died, and they replaced it with a one-wire setup - maybe.
It appears, at this point, only the wires in position 3 and 4 are functioning. Position 2 runs to the battery, position 4 into the dash (assuming this is running to my ammeter). So the Voltage regulator is really only powering the ammeter - but this seems to be working?
EDIT: It appears that the brown wire in position "4" should be for an "idiot light" which my 75 doesn't have - could it have been retrofitted to run the ammeter?
Now here is where I get confused again - The alternator does NOT connect to this voltage regulator. Nor does it connect directly to the battery. It connects here, at the harness:
Anyone know what that blue and white Toyota wire it is spliced to is? My understanding is that the "main power" wire is the solid white one, above it, which I will get to in a moment.
THE PROBLEM: It would appear, based on the plug on the back of my alternator (connectors look like [ || ]) that it should be EXTERNALLY regulated. All Internally regulated GM alternators had a connector that looked like: [- -] instead.
So, at this point, the alternator appears to have nothing regulating its current - or it is internally regulated and the Chevy forums are lying...
Would the truck run with an unregulated alternator, or would it be burning up all over the place?
Now, the MAIN POWER line to the harness is wired directly to the battery, with no fusible link -
It also appears that the connector is cracked, and they simply has a spade connector electrical taped in...or maybe they cracked the connector to install the spade? not sure. Either way, the red wire runs straight to the battery, and the white wire runs into the main harness. I'm assuming I should put an inline fuse, or a fusible link, in place of the red wire?
To condense my questions:
1. What the hell is my Alternator set-up? Am I truly running "unregulated" voltage?
2. If I was going to set this alternator up ONE way, which setup is better (traditional, 3 wire, or 1 wire?)
3. What is the wire that my alternator is currently connected to?
4. Should the fusible link go in-line with the alternator, or in-line with the main power, running from the battery to the harness?
5. The brown wire in position "4" on the regulator should control the "idiot light" on a Chevy dash - which the 40 doesn't have...could this have been retooled to power the ammeter?
Things I've learned: I'm running an Autolite 7122 Alternator. Every store online selling one says it is externally regulated. What's weird is: It appears to be a "one wire" setup, as others have mentioned. HOWEVER - Apparently this truck used to run the traditional 3-wire setup - since the "mystery box" on the fender is a GM Voltage Regulator, and that unplugged wire labeled "ALT" runs back to the regulator. The regulator also taps into the battery by one of the two smaller red cables (at least it did, until I broke it
), and the last wire coming out of the regulator runs to the dash - so I'm assuming that's my ammeter connection.Long story short, it appears that I'm running the remnants of 2 different GM Alternator setups. Sounds like the initial 3-wire one died, and they replaced it with a one-wire setup - maybe.
It appears, at this point, only the wires in position 3 and 4 are functioning. Position 2 runs to the battery, position 4 into the dash (assuming this is running to my ammeter). So the Voltage regulator is really only powering the ammeter - but this seems to be working?
EDIT: It appears that the brown wire in position "4" should be for an "idiot light" which my 75 doesn't have - could it have been retrofitted to run the ammeter?
Now here is where I get confused again - The alternator does NOT connect to this voltage regulator. Nor does it connect directly to the battery. It connects here, at the harness:
Anyone know what that blue and white Toyota wire it is spliced to is? My understanding is that the "main power" wire is the solid white one, above it, which I will get to in a moment.
THE PROBLEM: It would appear, based on the plug on the back of my alternator (connectors look like [ || ]) that it should be EXTERNALLY regulated. All Internally regulated GM alternators had a connector that looked like: [- -] instead.
So, at this point, the alternator appears to have nothing regulating its current - or it is internally regulated and the Chevy forums are lying...
Would the truck run with an unregulated alternator, or would it be burning up all over the place?
Now, the MAIN POWER line to the harness is wired directly to the battery, with no fusible link -
It also appears that the connector is cracked, and they simply has a spade connector electrical taped in...or maybe they cracked the connector to install the spade? not sure. Either way, the red wire runs straight to the battery, and the white wire runs into the main harness. I'm assuming I should put an inline fuse, or a fusible link, in place of the red wire?
To condense my questions:
1. What the hell is my Alternator set-up? Am I truly running "unregulated" voltage?
2. If I was going to set this alternator up ONE way, which setup is better (traditional, 3 wire, or 1 wire?)
3. What is the wire that my alternator is currently connected to?
4. Should the fusible link go in-line with the alternator, or in-line with the main power, running from the battery to the harness?
5. The brown wire in position "4" on the regulator should control the "idiot light" on a Chevy dash - which the 40 doesn't have...could this have been retooled to power the ammeter?
Last edited:
Coolerman
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Lord, you do indeed have a mess on your hands! It can be fixed, but you MUST do some basic protection stuff before you have a harness fire.
Electrical lesson #1 : The solid white wire that currently runs to the battery should have a fusible link installed. A fusible link is nothing more than a wire that is 2 gauges smaller than the wire it is protecting. In this case it is a 14ga wire. It is wrapped in a heat resistant insulation. It is generally about 3-4 inches long, so even though it's two gauges smaller, it dose not present a large amount of resistance to the power circuit. It acts like a very slow blow fuse. It will allow the entire system current to flow without melting. However, if you dead short the main charge wire it WILL melt BEFORE the larger main charge wire, thus saving the harness from a fire.
You need my 72-78 Fusible Link Kit AND the connector that attaches to the white wire coming out of the harness.
Electrical Lesson #3: The large White wire with Blue strip is the alternator B+ wire. It comes off the back of the B+ terminal on the alternator as a 10 ga wire, runs into the main harness where a smaller 12ga White/Blue wire is spliced to it. The 10 ga wire feeds the output of the alternator to the AMP Gauge - terminal. The smaller 12ga White/Blue wire goes to the AM terminal on the key switch. The charge current goes through the meter (causing it to read + or - ) then on to the + side of the meter where the 10 ga solid white wire attaches. This solid white wire goes to the fusible link then to the battery +. The fusible link protects both the 10ga White and the 10ga White/Blue wires. Because it is so short in comparison to the longer 12ga White/Blue wire going to the key switch it will also protect it. What is not protected by the fusible link are the smaller 14 and 16 gauge wires that come off the key switch going to the fuse panel. If you get a short in one of those wires they will melt... period....
OK so the very first thing you should do it get the fusible link and connector. The second thing you need to do is get a red 2ga + battery cable and run it from the battery B+ to the starter. Then get a black 2 ga - battery cable and run it from the battery - to the frame. Then get a shorter 2ga black jumper cable and run it from the same point on the frame to a point on the engine block. This will get your grounds the way they are supposed to be and if you get the military ends will allow easier connection of accessories to the battery.
If your setup as it is, is charging the battery with the two pin plug to the alternator unplugged then you have a internally regulated alternator and can get rid of the voltage regulator. To verify the alternator is charging: Turn on the headlights for 5 full minutes. Turn the head lights off. Set your volt meter on DC 20 volts. Put the red lead on the battery + and the black lead on the battery -. Write down the reading. It should be between 12.7 and 13.2 depending on state of charge. Now start the truck and repeat the measurement. It should read between 13.0 and as high as 15.2 volts. It should gradually drop as the alternator charges the battery. If the reading is the same, or lower than the first reading, the alternator is not charging. If it consistently reads higher than 14.8 or higher then it is charging but is not being regulated.
So do all that and THEN you can start cleaning up the other messes...
Electrical lesson #1 : The solid white wire that currently runs to the battery should have a fusible link installed. A fusible link is nothing more than a wire that is 2 gauges smaller than the wire it is protecting. In this case it is a 14ga wire. It is wrapped in a heat resistant insulation. It is generally about 3-4 inches long, so even though it's two gauges smaller, it dose not present a large amount of resistance to the power circuit. It acts like a very slow blow fuse. It will allow the entire system current to flow without melting. However, if you dead short the main charge wire it WILL melt BEFORE the larger main charge wire, thus saving the harness from a fire.
You need my 72-78 Fusible Link Kit AND the connector that attaches to the white wire coming out of the harness.
Electrical Lesson #3: The large White wire with Blue strip is the alternator B+ wire. It comes off the back of the B+ terminal on the alternator as a 10 ga wire, runs into the main harness where a smaller 12ga White/Blue wire is spliced to it. The 10 ga wire feeds the output of the alternator to the AMP Gauge - terminal. The smaller 12ga White/Blue wire goes to the AM terminal on the key switch. The charge current goes through the meter (causing it to read + or - ) then on to the + side of the meter where the 10 ga solid white wire attaches. This solid white wire goes to the fusible link then to the battery +. The fusible link protects both the 10ga White and the 10ga White/Blue wires. Because it is so short in comparison to the longer 12ga White/Blue wire going to the key switch it will also protect it. What is not protected by the fusible link are the smaller 14 and 16 gauge wires that come off the key switch going to the fuse panel. If you get a short in one of those wires they will melt... period....
OK so the very first thing you should do it get the fusible link and connector. The second thing you need to do is get a red 2ga + battery cable and run it from the battery B+ to the starter. Then get a black 2 ga - battery cable and run it from the battery - to the frame. Then get a shorter 2ga black jumper cable and run it from the same point on the frame to a point on the engine block. This will get your grounds the way they are supposed to be and if you get the military ends will allow easier connection of accessories to the battery.
If your setup as it is, is charging the battery with the two pin plug to the alternator unplugged then you have a internally regulated alternator and can get rid of the voltage regulator. To verify the alternator is charging: Turn on the headlights for 5 full minutes. Turn the head lights off. Set your volt meter on DC 20 volts. Put the red lead on the battery + and the black lead on the battery -. Write down the reading. It should be between 12.7 and 13.2 depending on state of charge. Now start the truck and repeat the measurement. It should read between 13.0 and as high as 15.2 volts. It should gradually drop as the alternator charges the battery. If the reading is the same, or lower than the first reading, the alternator is not charging. If it consistently reads higher than 14.8 or higher then it is charging but is not being regulated.
So do all that and THEN you can start cleaning up the other messes...
- Thread starter
- #48
Lord, you do indeed have a mess on your hands! It can be fixed, but you MUST do some basic protection stuff before you have a harness fire.
Electrical lesson #1 : The solid white wire that currently runs to the battery should have a fusible link installed. A fusible link is nothing more than a wire that is 2 gauges smaller than the wire it is protecting. In this case it is a 14ga wire. It is wrapped in a heat resistant insulation. It is generally about 3-4 inches long, so even though it's two gauges smaller, it dose not present a large amount of resistance to the power circuit. It acts like a very slow blow fuse. It will allow the entire system current to flow without melting. However, if you dead short the main charge wire it WILL melt BEFORE the larger main charge wire, thus saving the harness from a fire.
You need my 72-78 Fusible Link Kit AND the connector that attaches to the white wire coming out of the harness.
Electrical Lesson #3: The large White wire with Blue strip is the alternator B+ wire. It comes off the back of the B+ terminal on the alternator as a 10 ga wire, runs into the main harness where a smaller 12ga White/Blue wire is spliced to it. The 10 ga wire feeds the output of the alternator to the AMP Gauge - terminal. The smaller 12ga White/Blue wire goes to the AM terminal on the key switch. The charge current goes through the meter (causing it to read + or - ) then on to the + side of the meter where the 10 ga solid white wire attaches. This solid white wire goes to the fusible link then to the battery +. The fusible link protects both the 10ga White and the 10ga White/Blue wires. Because it is so short in comparison to the longer 12ga White/Blue wire going to the key switch it will also protect it. What is not protected by the fusible link are the smaller 14 and 16 gauge wires that come off the key switch going to the fuse panel. If you get a short in one of those wires they will melt... period....
OK so the very first thing you should do it get the fusible link and connector. The second thing you need to do is get a red 2ga + battery cable and run it from the battery B+ to the starter. Then get a black 2 ga - battery cable and run it from the battery - to the frame. Then get a shorter 2ga black jumper cable and run it from the same point on the frame to a point on the engine block. This will get your grounds the way they are supposed to be and if you get the military ends will allow easier connection of accessories to the battery.
If your setup as it is, is charging the battery with the two pin plug to the alternator unplugged then you have a internally regulated alternator and can get rid of the voltage regulator. To verify the alternator is charging: Turn on the headlights for 5 full minutes. Turn the head lights off. Set your volt meter on DC 20 volts. Put the red lead on the battery + and the black lead on the battery -. Write down the reading. It should be between 12.7 and 13.2 depending on state of charge. Now start the truck and repeat the measurement. It should read between 13.0 and as high as 15.2 volts. It should gradually drop as the alternator charges the battery. If the reading is the same, or lower than the first reading, the alternator is not charging. If it consistently reads higher than 14.8 or higher then it is charging but is not being regulated.
So do all that and THEN you can start cleaning up the other messes...
Wow - Thanks for the detailed response! I'll definitely be in touch regarding the fusible link/connector. I have Mil-spec terminals in hand, and I'll be ordering the necessary ground wires next. I measured for all of them last night.
So, based on what you've said, and the wiring diagram I stole from your website, it looks like my current alternator is actually wired in just like stock - connected to the heavy gauge white/blue wire, with the heavy gauge white wire connected to the battery. However, it appears the alternator is internally regulated as opposed to externally, so the external regulation has been bypassed - sound right? The AMP meter seems to be working, I can see voltage drops when I turn on the headlights/blinkers/wipers/etc. and my battery hasn't died since I bought it 3 years (400 miles) ago.
My confusion arises because the shape of the plug on the back of my alternator, and the part number for the alternator, both claim that it's EXTERNALLY regulated...If the Alternator was running completely unregulated - would such a setup even work at all, or would something have melted by now?
I'll certainly check out the charging situation next time I'm up there - I broke the wire connector running from the battery to the voltage regulator, so I figured I wouldn't touch anything until I figured out if that was important...
Would installing an alternator that I know FOR CERTAIN is internally regulated be a good idea? Would it wire in the exact same way? I'd just bypass the idiot light terminal, but I'd like the AMP meter to keep doing its job.
It doesn't look that bad as most of the non-stock wiring is associated with the alternator. The alternator is probably not producing as it is externally regulated and it is not plugged in. What happens to the battery voltage when you plug it in?
For the stock wiring all of the power that goes in and out of the battery goes through the amp meter (except for the starter motor). That means that there is one wire at the battery + besides the starter motor cable. This wire should have a fusible link to avoid the possibility of a harness fire.
For the stock wiring all of the power that goes in and out of the battery goes through the amp meter (except for the starter motor). That means that there is one wire at the battery + besides the starter motor cable. This wire should have a fusible link to avoid the possibility of a harness fire.
- Thread starter
- #50
Agreed - the deeper I dug last night, the more I realized that the PO actually did a pretty decent job of sequestering the GM stuff from the rest of the harness. It LOOKS like a mess, and most of his connections are just "twisted and taped" or done with wire nuts, which will all need to be addressed, but aside from the missing grounds/fusible links - I think it's starting to make sense.
As I mentioned in my response to Coolerman - I haven't actually measured the voltage at the battery yet. That was the plan last night until I broke the wire running from battery to voltage regulator and figured I should leave well enough alone until I deciphered everything.
All I know is that the AMP Meter in the cab definitely reads drains on the system (drops when headlights are on, fluctuates when blinkers fluctuate) and the battery hasn't died, BUT - there seems to be very little charge in the system. If I have my headlights/windshield wipers on and I'm sitting at idle, my blinkers don't work.
Yep - and I believe, looking at Coolerman's wiring diagram, that this is the case here. The Alternator hooks into the blue/white wire running to the (-) terminal on the AMP Meter, and the White Wire off the AMP meter (+) side runs straight to the battery - just missing the fusible link.
Coolerman
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I bet the alternator is NOT charging. Determine if it is, because you can't proceed with cleaning it all up until you know if it works or not.
If it is not charging as it is, plug the two pin connector into the alternaotr (connecting the regulator to the alternator) and see what happens. Alternator could be bad, and/or the regulator could be bad.
If it is not charging as it is, plug the two pin connector into the alternaotr (connecting the regulator to the alternator) and see what happens. Alternator could be bad, and/or the regulator could be bad.
- Thread starter
- #52
Come to think of it, you may be correct - when I bought the truck, it had what looked to be a fairly new Interstate battery. I had a shop rebuild my power steering system. It sat in their shop for about 2 months, during which time the battery died, couldn't get it to hold a charge, so they replaced it. That said, the new battery has been in there for the better part of 3 years, mostly sitting, with limited driving (probably 5-10 hours). I'm surprised it would have made it this long without dying, if the alternator wasn't charging. I imagine it wouldn't last 20 minutes without an alternator charging it...
Sounds like I'll need to repair/replace the wire to the voltage regulator, then check the charge on the battery, fire it up, and see if the alternator charges it. If not, I'll plug in the regulator and check again.
PS - I sent you a PM regarding the Fusible links/connectors.
@Coolerman you've got mud mail
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- #54
So while I have peoples' attention -
I've been digging around trying to figure out how best to wire in an internally regulated alternator, and it looks like it would be pretty easy. In fact, it seems like, with the external regulator currently disconnected, like it is - that's pretty much what I have.
Simply put - It would wire up to something like this, correct?
Only thing I'm not sure about is whether I can hook the voltage sensor up to the battery. I've heard it's not a great idea just to jump it over to the BAT cable on the alternator because then the alternator won't account for voltage drop through the lines...but I'm not sure hooking it up to the battery is the right answer either...
I'm pretty sure I should just be able to leave the "warning light" terminal naked, since there's no warning light to run it to.
Thoughts?
I've been digging around trying to figure out how best to wire in an internally regulated alternator, and it looks like it would be pretty easy. In fact, it seems like, with the external regulator currently disconnected, like it is - that's pretty much what I have.
Simply put - It would wire up to something like this, correct?
Only thing I'm not sure about is whether I can hook the voltage sensor up to the battery. I've heard it's not a great idea just to jump it over to the BAT cable on the alternator because then the alternator won't account for voltage drop through the lines...but I'm not sure hooking it up to the battery is the right answer either...
I'm pretty sure I should just be able to leave the "warning light" terminal naked, since there's no warning light to run it to.
Thoughts?
- Thread starter
- #55
Friday night bump for more info -
Tried reading the other threads on GM alternators - but I can't seem to find a good answer to whether or not the above is correct...
Is my diagram above anywhere close, in terms of wiring in an internally regulated alternator?
BAT wire from alternator connects to the blue/white charging wire to the Ammeter
White Wire off the (+) side of the ammeter goes to the battery (adding fusible link)
Voltage Sensing line goes straight from Alternator to battery
Warning light terminal gets ignored.
Tried reading the other threads on GM alternators - but I can't seem to find a good answer to whether or not the above is correct...
Is my diagram above anywhere close, in terms of wiring in an internally regulated alternator?
BAT wire from alternator connects to the blue/white charging wire to the Ammeter
White Wire off the (+) side of the ammeter goes to the battery (adding fusible link)
Voltage Sensing line goes straight from Alternator to battery
Warning light terminal gets ignored.
The actual wiring depends on the specific alternator. Many used switched power to engergize the alternator. Some require a diode in the circuit to prevent feeding back power to the ignition after shut off. Some need a light bulb or resistor.
I'd love to answer Rick... but it would hurt more than help... bump for Rudi (@bj40green ) and/or Mark ( @Coolerman ) or anyone else that knows your answers.
- Thread starter
- #58
If it helps - I'd be looking at a typical GM 10SI or 12SI
bj40green
Tssss, tssss
I just jumped in, thanks to pngunme, and didn't read the whole thread. Just the part about hooking up. Here is an advice for hooking up the S (Sense) wire.
HTH,
Rudi
Last edited:
71FJnick
SILVER Star
Bj40green posted a diagram for, I believe a 3 wire alternator, if you truly have a 1 wire GM unit, the the 1 wire would just go to either the battery OR the main wire to the fuse box or dist block. The other wires are for the charge light.
MAD Electronics has some good info, actually after reading it you'll probably want to go with a 3 wire GM setup... I did. The advantage of the 3 wire is that the sensing wire can be at the fuse block and the charge wire can be at the batt. With a 1 wire set up, like you have the sensing wire and charge wire are the same.
MAD Electronics has some good info, actually after reading it you'll probably want to go with a 3 wire GM setup... I did. The advantage of the 3 wire is that the sensing wire can be at the fuse block and the charge wire can be at the batt. With a 1 wire set up, like you have the sensing wire and charge wire are the same.
