Idiot Lights to Gauges conversion questions

[MattyBs71]

Hi all,

I am working on changing my truck from idiot lights to stock gauges. I have found the tips on the GMC Pauls website which are great but I have hit a snag.

I have moved all the wires it says to in the dash wiring harness plug but have run into the final two wires I am stumped at.

When looking at the tips is says that:
1-Black with white stripe (alternator) This runs from the 12 R from voltage regulator and should have a inline fuse.

Ok the voltage regulator is located on the core support correct? I see the black and white wire with the inline fuse still in tact. I follow the wire to the fire wall where it disapears into the wiring block on fire wall, I look inside truck under dash to try and see where it goes and I can't find it.

Quesion:
Should I just splice into it before it goes thru the fire wall and run it to dash harness position 1?

2nd issue:
Do all trucks have a junction block near battery on passenger fender? I don't see one on my truck.

GMC Pauls says in reference to position 12 on dash wiring harness:
12-Black/w brown stripe use wire ran from the junction block near battery mounted to passenger side fender with a inline fuse located at junction block end.

Question: Am I just running a wire from the positive terminal on my battery with an inline 4 amp fuse to the dash wiring harness position 12 ?


Lastly my truck came with the idiot gauges so it has a brown Generator wire that was in the dash wiring harness do I just cap off this wire and not use it now for anything?
I have already fried one circut board and I don't want to do it again to another. Please help!

If I am making no sense here let me know.

[GMCPaul]

Matt I've replied to your email and am also replying here in case others have the same problem, your problem stems from it appears you have a gauge dash forward lamp harness and a non-gauge dash harness.

from what you describe here
***Ok the voltage regulator is located on the core support correct?(YES IT IS ON CORE SUPPORT) I see a black and white wire with the inline fuse still in tact which is fed off that 12 R wire coming from Voltage regulator and Alternator. I follow the wire to the fire wall where it disapears into the wiring block on fire wall, I look inside truck under dash to try and see where it goes and I can't find it ****

this description is of a forward lamp harness that is for a gauge truck so someone has either replaced the forward lamp harness at some point or put a different cab on the chassis that came from a non-gauge truck with the idiot light dash harness still installed, the blk/white wire with fuse is not present on a non-gauge truck and since the dash harness is non-gauge there is no wire terminal exiting inside the truck as it would exit the bulk head connector in same position on inside as its in on outside. So you should cut it at bulk head and then connect to it and continue it into truck cab and connect to the #1 position as you assumed in your description.

If you don't currently have a junction block on passenger side fender you can instead run the 2nd wire from the 12g red wire feeding power from altenator to battery at the battery positive terminal with a 4amp wire inline to the #12 position.

The #8 position 20g brown wire on your idiot light cluster is not re-used you can cut it off or tape it or cap it off, if cutting make sure that if you cut it at bulkhead connector to remove from harness that you do not also cut 24 gauge brn / white wire that is also tied into the bulkhead connector on the inside as it feeds to the ignition circuit & headlight circuit on gauge & non-gauge trucks.

You might check out the cowl wire gutter to see if possibly they coiled up the blk wire w/4amp fuse inline and placed it in the wire gutter to clean up under hood appearance as I have found this to be the case on a similar truck we bought that had the original idiot light forward lamp harness replaced with a gauge harness. Under the hood its all black and is connected to the position just below where the blk/white wire with 4 amp fuse enters the bulk head so you should be able to reverse trace it from the bulk head connector to see if its cut off or coiled up.

If you have any further questions don't hesitate to ask.

GMCPaul

[MattyBs71]

Paul,
I have found that black wire you speak of above, it is spiced into a red wire (looks like alternator wire that feeds from battery) that hooks right up to the positive terminal on the battery, there is no inline fuse anywhere on it, shall i put a 4 amp inline fuse on it and then see if it goes thru the bulkhead connector and splice into it under the dash, or if not just splice into before the bulkhead and run it to position 12 on the gauge cluster harness? Thank you for your time you are very very helpful!

[MattyBs71]

Clarification, I know the black wire goes to the bulk head on engine side as it is right next to black w/ white stripe wire, just not sure if it goes thru into cab on the other side, I have to go re-search and today is fathers day and I don't think I'll be doing it today!

[GMCPaul]

Matt the black wire you will find does not enter the cab at the bulkhead connector as the idiot light dash harness has no provision for it that spot on the underdash harness bulkhead connector will be empty the same as the b/w wire one is empty so you'll need to cut both off and run them to their respective spots on the dash cluster connector.
Hope you had a great fathers day!!!!!
My Very Best Regards
Paul @ GMCPauls

[MattyBs71]

Hopefully this will be my last question...
My truck is sans a junction block I need some help. The 12 R wire that runs from the alternator to the junction block and then to the battery has no inline fuse on it. Should it have one? If so what size? The truck ran and drove fine without one but I'm thinking it should have one in case something happend down the road I would like my alt not to fry. I have everything else hooked up and ready to go, I even got my new circut board today for the gauges and put that in.

[GMCPaul]

Sorry I missed answering the question you asked on fuse, the 12gauge red wire does not have a fuse inline on it, however the black wire spliced onto it that is supposed to be connected to the 12g red wire at your missing junction block that black wire should have a 4 amp fuse inline on it.
Have a great week!!!
GMCPaul

[MattyBs71]

Paul, thank you for all your help, I know who I will be ordering parts from, from now on! You kickass man!

[chuckmc8]

Tagging into an older thread so that anyone interested can read up to this point-
My question-
I have used GMC Pauls great article on the FAQ page and also this thread but I need clarifaction on a couple points.

If I understand correctly

On the "new" plug configuration, #1 ties into the large red wire on the back of the alternator with a new wire and 4 amp fuse.
So this is "hot" all the time, right? Isnt that basicaly the same as running it to the battery terminal?

Position #12 requires a new wire to be ran from the junction block (or pos batt term) and add 4 amp fuse there as well. Also 'hot" all the time.

Seems like one of these whould be IGN position power only. IS that #1 and I missed the instruction?

Also, there are two wires "left over"from the idiot gauge installation, the dark blue that was the oil warning and the brown one.
Can these be incorporated to use for the #1 and #12 wires that I asked about above and just pick them up in the engine compartment instead of runnning new wires?

I am also adding an internally regulated alternator now as well as a van tilt column with a neutral saftey switch.


Thanks for the help-

[fixit-p]

Originally Posted by chuckmc8

Tagging into an older thread so that anyone interested can read up to this point-
My question-
I have used GMC Pauls great article on the FAQ page and also this thread but I need clarifaction on a couple points.

If I understand correctly

On the "new" plug configuration, #1 ties into the large red wire on the back of the alternator with a new wire and 4 amp fuse.
So this is "hot" all the time, right? Isnt that basicaly the same as running it to the battery terminal?

Position #12 requires a new wire to be ran from the junction block (or pos batt term) and add 4 amp fuse there as well. Also 'hot" all the time.

Seems like one of these whould be IGN position power only. IS that #1 and I missed the instruction?

Also, there are two wires "left over"from the idiot gauge installation, the dark blue that was the oil warning and the brown one.
Can these be incorporated to use for the #1 and #12 wires that I asked about above and just pick them up in the engine compartment instead of runnning new wires?

I am also adding an internally regulated alternator now as well as a van tilt column with a neutral saftey switch.


Thanks for the help-

Are we talking about a stock external shunt type ammeter if so one wire from the the ammeter goes to the batt junction block with 4 amp fuse and the other wire goes to the alt buss also with a 4 amp fuse both wires hot all the time and on opposite ends of the same wire this wire is your shunt the ammeter reads the voltage drop between these two points if you have a volt meter wire to switched power at your fuse box or main power relay if it's a full flow ammeter simply throw it away

[chuckmc8]

OTAY- heres a foto of my dash so you cansee what I have

[chuckmc8]

SO THEN........as i said I am also changing to internal reg alternator and have both cab and under portion harness at my feet here in the house.

NOTE TO SELF- Next time, wait till the wife leaves for work to use the kitchen sink to clean wiring harness.

I am trying to modify my harness so that it doesn't look 'farmerized'....I love that term!!

So I want to remove the old external regulator wiring. No bust
here, I can use the color diagram to do that.

And here's a question combo of the 'changing from idiot lights and changing to internal regulator alternator.


TODDTHEODD's and GMC Paul's great info I am tryiing to make together-

Heres Todds info-"Now the blue wire, which is just an extension of the brown wire, connects to the tab on the right (number 1 tab). The BROWN wire runs the the idiot light/gauge in the dash and is there for resistance to the internal voltage regulator. You can not skip this as it tells the regulator what it needs to be doing and when."

And GMC paul's help on the gauge plug wiring rearrangment-

"The #8 position 20g BROWN wire on your idiot light cluster is not re-used you can cut it off or tape it or cap it off, if cutting make sure that if you cut it at bulkhead connector to remove from harness that you do not also cut 24 gauge brn / white wire that is also tied into the bulkhead connector on the inside as it feeds to the ignition circuit & headlight circuit on gauge & non-gauge trucks.

So, Wadda I do with the brown wire when I change alternators?

in the foto below the two loose wires are the BLUE on the left and the BROWN in question, on the right.

Thanks for the help

[fixit-p]

If you are installing a 12SI alt. you could possibly use the wire to turn on the alternator (alt. term. #1) the wire would need to be connected to an ign source and have a resistance or diode installed. Your idiot light used to provide this resistance. I can see on my 69 inst. cluster that there is a blank idiot light next to the brake idiot light It would be nice if you could install a light there and wire it between ign and the brown wire.

[Delo69]

Ok I'm confused as hell..I'm in the process of this as well..I also have a internal reg alternator. Looking at this thread..I have some questions.

1. I have a red wire from the junction box to the battery cable, I have another red wire from the junction box that runs across the front of my truck to where the external volt reg was (clipped), I have a red wire from my alt. (clipped) and another red wire that goes into the firewall (clipped)...So do all of these need to be joined?

2. I moved all the wires per GMC Pauls site and have the blue and brown left. Do I tape them off?

3. Reading the GMC Paul Tips for the conversion the #1 and #12 spot I need to run wires with inline fuses..#1 need a wire to be tapped into the red wire coming off the alternator...the #12 need a wire from junction box to the #12 spot.. Is that correct? Cause to me if I do that its like running the #1 and #12 to the battery..and then ontop of that how do you wire them into the gauge plugs without the clips?

I'm jonesing to get my truck put together and running so she can get new tires and the wife and I can go for a ride.

Sorry I'm new at wiring and thanks in advance to anyone who can help.

[VetteVet]

Originally Posted by Delo69

Ok I'm confused as hell..I'm in the process of this as well..I also have a internal reg alternator. Looking at this thread..I have some questions.

1. I have a red wire from the junction box to the battery cable, I have another red wire from the junction box that runs across the front of my truck to where the external volt reg was (clipped), I have a red wire from my alt. (clipped) and another red wire that goes into the firewall (clipped)...So do all of these need to be joined?

2. I moved all the wires per GMC Pauls site and have the blue and brown left. Do I tape them off?

3. Reading the GMC Paul Tips for the conversion the #1 and #12 spot I need to run wires with inline fuses..#1 need a wire to be tapped into the red wire coming off the alternator...the #12 need a wire from junction box to the #12 spot.. Is that correct? Cause to me if I do that its like running the #1 and #12 to the battery..and then ontop of that how do you wire them into the gauge plugs without the clips?

I'm jonesing to get my truck put together and running so she can get new tires and the wife and I can go for a ride.

Sorry I'm new at wiring and thanks in advance to anyone who can help.

I don't know where you found this old thread but here is a good thread for you.
http://67-72chevytrucks.com/vboard/s...d.php?t=495265

[WIDESIDE72]

I will be doing this same swap soon. THanks for the help!

[808_67C10]

Okay, I have to bring this one back due to an issue I am having....

I followed the GMC Paul's website and swithed all the pins as required.
I have the #1 pin going to the alternator with a 4 Ohm fuse (Hot with the ignition)
The #12 is spiced into the #3 pin on my volatge regulator and it has a 4 Ohm fuse before it hits the dash too. (Always Hot)

The problem I have is, its drained my battery down to nothing overnight the day i plugged in my dash. The amameter is pegged to the left too... now that its dead, its pegged to the right..

Anyone have any sugestions?

[GMCPaul]

Originally Posted by 808_67C10

Okay, I have to bring this one back due to an issue I am having....

I followed the GMC Paul's website and swithed all the pins as required.
I have the #1 pin going to the alternator with a 4 Ohm fuse (Hot with the ignition)
The #12 is spiced into the #3 pin on my volatge regulator and it has a 4 Ohm fuse before it hits the dash too. (Always Hot)

The problem I have is, its drained my battery down to nothing overnight the day i plugged in my dash. The amameter is pegged to the left too... now that its dead, its pegged to the right..

Anyone have any sugestions?

No where in my instructions says to connect the #12 to the voltage regulator. You are supposed to connect to the junction block. Then the junction block is connected to the battery by a fusible link. So connecting it directly to the voltage regulator could be your problem. Also its only supposed to be approx. 6"-1' from the positive battery connection to read correctly.
Paul @ GMCPauls

[808_67C10]

Thanks for the quick response. I didnt connect it to the Volt Reg, its connected to the HOT wire going from the battery into the #3 on the Volt Reg so, essentially, it is coming from the + on the battery. My truck was a straight 6/now a V8. I dont have the junction box IVO the battery... where else can I hook it up that I can adhere to the 6ft 1inch wire length.

[VetteVet]

Here is how the factory did it. Notice that the shunt wire goes across the top of the radiator and connects to the no. 3 wire which is a junction point for the alternator, the feed wire, the no.12 wire and the sensor wire for the voltage regulator. The shunt wire is the 6 foot 1 inch wire. It;s no. 12 gauge and the no. 1 wire connects to the passenger side end of it at the fender junction with the fusible link off the battery positive terminal.

[808_67C10]

Please read my previous post and how. I have it hooked up. I don't have the junction box off the battery. What are alternative connection points? At this point, I don't even care if my ammeter works at all... I need my fuel guage and turn signal indicators. Too bad there isn't just a volt meter conversion to avoid all these problems.


Based off the schematic, both 12 and 1 are always hot both coming off the battery? Is this correct? That doesn't make sense since u wouldn't want 2constant hots runnin a guage panel u only need when the key is on?!?!? I am lost here.

Posted via Mobile Device

[VetteVet]

Originally Posted by 808_67C10

Please read my previous post and how. I have it hooked up. I don't have the junction box off the battery. What are alternative connection points? At this point, I don't even care if my ammeter works at all... I need my fuel guage and turn signal indicators. Too bad there isn't just a volt meter conversion to avoid all these problems.



Posted via Mobile Device

I did read your previous post and that's why I posted the diagram to show how the factory did the wiring.You will have to wire the battery gauge wires near the battery and to a point where the alternator makes a junction with the other power wires in the harness.

A good idea for this is a terminal block on the left radiator support near the left headlight. The older trucks used the horn relay for that but the company has moved the horn relay inside the cab. The alternator output wire would be connected there along with the shunt wire from the battery. The shunt also serves as the charging wire for the battery.

It is much easier to replace the battery gauge with a voltmeter and they actually tell you more about the system. There are threads about making the change or you can add one below the dash.

Based off the schematic, both 12 and 1 are always hot both coming off the battery? Is this correct? That doesn't make sense since u wouldn't want 2constant hots runnin a guage panel u only need when the key is on?!?!? I am lost here.

This is correct, they are both hot but they don't feed the gauge panel, they only feed the gauge. The gauge uses the shunt wire by connecting at each end of the wire and reading the voltage of the battery on one terminal and the alternator output on the other terminal. It translates those readings into the charge or discharge reading on the gauge needle, depending on whether the battery charge is higher or lower than the alternator output voltage.

The gauge panel is fed by a pink wire of the fuse panel from the cluster feed fuse. This pink wire goes to the terminal 3 of the dash plug and from there to the fuel gauge where the circuit board joins it to feed the rest of the gauges.
Other lights are fed by other wires. and the dash cluster must be well grounded to the cab and to the battery negative side of the circuit in order for every thing to work correctly.

[808_67C10]

got it... if what your saying is correct.. why (if #12 is unplugged) will nothing in my guage panel work? It is grounded through the cab wiring and I didnt have any issues with my previous idiot light panel.

I am just going to have to keep chasing wires and checking them. thanks for your help.

[VetteVet]

I can't explain why your gauge panel works off the no.12 wire. It should power off the no. 3 terminal where the pink wire for the fuel gauge power is pinned, When the key is on. You may have a problem with the circuit board. The battery gauge should have no effect on whether the cluster powers up or not. Here is a thread that may help you figure it out. Notice that there is a voltmeter in the place of the battery gauge which refers back to your earlier question in the thread, post 21.

............http://67-72chevytrucks.com/vboard/s...d.php?t=568662

[808_67C10]

I am torn at this point. The guage panel is in great shape and I have 2... both have the same issue.

Are there alternate connection points for #1 and #12? Do they both need to be HOT all the time or just HOT with the ignition? or 1 each?