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#1 |
Registered User
Join Date: Feb 2013
Location: Conway, AR
Posts: 17
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So I have a 67 c10 that has butchered wiring like you wouldn't believe. After some bad info on dash lights I fried the printed circuit from the original dummy light cluster. So, am replacing it with a gauge cluster out of a 70-72 model c10.
I've read GMC Paul's write-up, and a few million other Q&A's... My problem is wiring of the alternator and battery to the respective #1 and #12 slots on the loom plug... 1. I have no junction block 2. This truck was in some way converted to an internally regulated alternator when the PO also did an HEI conversion So where do I get these wires from so that my gauges read properly? Any help would be great! |
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#2 | |
Registered User
Join Date: Jan 2013
Location: Mickleton, NJ
Posts: 1,776
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
The junction block is just a spot to connect into the wire that feeds the fuse block. Tap into that wire anywhere (t-tap, quick splice, etc.) and it should work. I went from the alternator output and the junction block on my truck, and the gauge works fine.
__________________
Shawn 1970 Chevy C-10 SWB, 350, TKO 600 5 speed My build http://67-72chevytrucks.com/vboard/s...d.php?t=559881 |
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#3 |
Registered User
Join Date: Feb 2013
Location: Conway, AR
Posts: 17
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Re: Dummy Light to Gauge dash swap chaos! Help?
Thanks for the quick and simple response! Everything I've been reading til now just seems to over-complicate this whole thing!
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#4 | |
Registered User
Join Date: Jan 2013
Location: Mickleton, NJ
Posts: 1,776
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
I pretty much just followed the instructions on GMC Pauls site to the letter, and tried not to let myself question anything....LOL. I start double thinking stuff like this and talk myself into not believing what others have done. My wiring was a pretty bad hack job when I started, and I have pretty much everything sorted out now. All I have to do still is connect the sensor wire for coolant temp when I get around to swapping engines. Current engine doesn't have the spot on the head for it.
__________________
Shawn 1970 Chevy C-10 SWB, 350, TKO 600 5 speed My build http://67-72chevytrucks.com/vboard/s...d.php?t=559881 |
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#5 | |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
You will have to have the 4 amp fuses in the wires to protect the gauge and you have to connect the wires to the alternator and to the battery but you cannot run the alternator directly to the battery or to the starter terminal. You have to have a shunt wire between the alternator and battery connections. If whoever converted your alternator ran the alternator output wire directly to the battery then the gauge won't work. Study the diagram and you can see the connections and the shunt. Here is the junction on my truck which has the idiot light dash so I will have to connect the ammeter wire there. I suppose it can be connected right on the alternator as long as the alternator wire doesn't go directly to the battery. There is supposed to be a junction bolt on the right inner fender by the battery. This is where the fusible link from the battery and one end of the shunt wire is supposed to go. That is where the other gauge wire goes.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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#6 | |
Senior Member
![]() Join Date: Mar 2000
Location: Rockville,In. USA
Posts: 3,720
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
Here's a picture of the junction block that's supposed to be on all of these trucks passenger side fender near the top just under the hood about 12"-16" back from the front of fender and all wires attach to the center metal stud. Paul @ GMCPauls |
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#7 | |
Senior Member
![]() Join Date: Mar 2000
Location: Rockville,In. USA
Posts: 3,720
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
Doing this the gauge then reads output at back of alt. & again just before the battery and it senses the difference thus displaying the amount of current drawn by the battery. Make sure you install the fuses inline on both wires. On a stock vehicle harness the fuses are approx. 12-14" from the alt & junction block. Paul @ GMCPauls |
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#8 | |
Senior Member
![]() Join Date: Mar 2000
Location: Rockville,In. USA
Posts: 3,720
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
Paul @ GMCPauls |
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#9 | |
Registered User
Join Date: Jan 2013
Location: Mickleton, NJ
Posts: 1,776
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
__________________
Shawn 1970 Chevy C-10 SWB, 350, TKO 600 5 speed My build http://67-72chevytrucks.com/vboard/s...d.php?t=559881 |
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#10 |
Registered User
Join Date: Jan 2013
Location: Mickleton, NJ
Posts: 1,776
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Re: Dummy Light to Gauge dash swap chaos! Help?
Not so sure thats true. I have a wire straight from my alternator to the positive post on the battery and nothing else, and the gauge works well for me. Don't know how accurate the gauge is, but it gives me the indication I expect from a working alternator.
__________________
Shawn 1970 Chevy C-10 SWB, 350, TKO 600 5 speed My build http://67-72chevytrucks.com/vboard/s...d.php?t=559881 |
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#11 | |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
The soldered junction is on the other side of the truck in the harness behind the left head light and the four wires that are soldered together are the Alternator charging wire, the voltage regulator (external) sensing wire, the other end of the battery charging wire (Shunt) and the power feed to the firewall connector for the cab. This is how the electrical diagrams for 67 to 72 show the junction and it's how Mad Electrics website shows it. .... http://madelectrical.com/electricalt...evymain1.shtml The only difference is on the 66 and earlier trucks the horn relay is used as the junction block but in 67 they moved the horn relay inside the cab but kept the splice. here's the splice. These are in their website I can't see how connecting all the power wires on the right fender junction would allow the battery gauge to work because it eliminates the battery charging wire ( the Shunt) which the gauge uses to read the voltage differential between the alternator output voltage and the battery state of charge. In fact the battery gauge would see the same voltage all the time because it would be reading the voltage at the alternator and the same voltage where the alternator connects to the right fender junction. I removed the soldered junction in my truck and added a terminal block but I kept the battery charging wire and the alternator regulator sensing wire there and connected an 8 gauge wire from the alternator output terminal to them. On the right side I used a junction block for the other end of the battery charging wire with a maxi fuse instead of the fusible link. I'm connecting the 1 and 12 wires with fuses to each end of the battery charging wire so the gauge will be wired like the diagrams. I've also converted to the internal . regulated alternator do I'm anxious to see how it works. It looks sorta like this.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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#12 | |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
What happens when the truck's running and you turn on the lights and wipers? The gauge should flicker over to discharge and then return to just past center. It's possible that the alternator feed wire is acting as the shunt and the gauge is able to read a difference between the alternator and battery voltages. The GM engineers calibrated the shunt wire by length, gauge, and resistance to correspond to the battery gauge and I would think that modifying either of those would affect the accuracy of the gauge. In actuality the gauge has been replace by a voltmeter which is more accurate, gives better information, as well as being a lot easier to wire in and hookup. My argument is not about how any body wires the battery gauge or whether it works or not. My argument is how the factory did it based on what I've read and seen including how my truck was set up.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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#13 | |
Registered User
Join Date: Jan 2013
Location: Mickleton, NJ
Posts: 1,776
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
I understand what you are stating in terms of "factory correct". My truck is so far from that that its not even similar at this point. But what you stated is "cannot", and that is different from saying "its not factory correct". My point was to have an ammeter that works in the cluster, which seems to be what I have with my highly modified system. My battery gauge will read slightly left of the center line while cranking, and will stay there until the engine rpm's exceed 1400 and the alternator excites. Then it jumps all the way right and slowly comes back down to just slightly right of center. As I turn more stuff on, it moves further right, which in mind is showing that the alternator is increasing output, as it should. If it goes the other way, the draw is exceeding output, which would mean either the alternator can't keep up or is not working. I also have a voltmeter, but its only reading what it seems in the fuse block, which can drop quite a bit when things engage. I'm slowly adding in relays to keep that from happening. FWIW, I have a lot of added electrical load with the AC system and the dual electric fans.
__________________
Shawn 1970 Chevy C-10 SWB, 350, TKO 600 5 speed My build http://67-72chevytrucks.com/vboard/s...d.php?t=559881 |
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#14 | |
Msgt USAF Ret
![]() ![]() Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,714
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Re: Dummy Light to Gauge dash swap chaos! Help?
Quote:
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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#15 |
Registered User
Join Date: Feb 2013
Location: Conway, AR
Posts: 17
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Re: Dummy Light to Gauge dash swap chaos! Help?
Thanks for all the info guys! Honestly to do this all right I'd probably be best off re-wiring it from the ground up, but at least for the time being I need this to be a running/driving vehicle again
![]() Let's just say after two dash fires and a slew of other issues, where I'm at now is light years ahead of where I was when I started! ![]()
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'67 C10 SWB Stepside |
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