The Stovebolt Site Forums The Shop Area The Electrical Bay Question re: aftermarket harness and power to gauges.

I have a Speedway Motors aftermarket harness which provides one 12v ignition wire to power any and all electrical gauges. I currently have it providing power to my tach, but would also like to use that same wire to power my volt meter, and probably later to the fuel gauge. My electrical skills border on beginner/intermediate, so I was curious as to how you all would tackle this, before I just reach for the can of wire nuts and "rig" it.

Thanks in advance!

1. Give speedway harness part number.
2. Advise how many electrical gauges? Which ones?
3. Do you now have same wire for gauges and for tach? Is that what you said? or it's just going to tach, nowhere else?
4. You added a volt meter somewhere?
5. Using original gauge cluster? If not, explain.

After answers, I will advise a plan.

Thanks! See below:

1. Give speedway harness part number.

910-64022. 22-circuit harness.

https://www.speedwaymotors.com/22-Circuit-Universal-Automotive-Aftermarket-Wiring-Harness-Kit,229874.html

2. Advise how many electrical gauges? Which ones?

Right now I have just the tach hooked to the single harness wire. The other one I'd like to hook up on the same wire is an aftermarket volt meter.

3. Do you now have same wire for gauges and for tach? Is that what you said? or it's just going to tach, nowhere else?

Yes, same wire for gauges and tach.


4. You added a volt meter somewhere?

Yes, it was in one of those 3 packs with temp and oil pressure.

5. Using original gauge cluster? If not, explain

No, not using the orig gauges at this time. Beyond the Speedo, I have no idea what the condition of the other gauges is (yet).

1. 3A Pink goes to Positive terminal on HEI
2. 121 White goes to tach terminal on HEI
3. Gauge power, including gas and volt are supplied by 39 Pink. When ready, I will advise this hook up.

(This is all provided you have ignition switch wires and other wires done per instructions.)
Question me if I'm wrong or you need further. If you need help with ignition switch, provide pic of rear of switch and it's markings.

Some of your gauges may or may not end up being mechanical instead of electric. That would be temp and oil. Some have a tube to the sender instead of a wire.
I assume you are abandoning the Ammeter? That's fine. Most harnesses do not support it.

Thanks for the review! Yep, 39 pink is the power wire I am referencing. It is currently connected directly to the red power wire of my tach. But if I need that same power wire to run my volt meter/ammeter, my question is how is the best way to connect that additional gauge to that same 39 wire.

121 was also funny, as they provide that to run from the green wire of the tach to the HEI. But, the green wire of the tach itself is over 4 feet long, so I did not need 121 at all. I could still see someone using both wires though, just bc "the instructions said so"

You are installing a new wire harness with it's own fuse box. Wires are routed from the fuses to various components. Different wires have different fuses and are connected inside the fuse box to accomplish a safe and proper electrical system. Some wires from the fuse box are "switched hot" and some are "always hot". The ignition switch turns on the hot fuse bank. Some wires are direct from the battery and etc. I don't know, and you don't know, exactly how all the circuits are internally wired and engineered. I have spelled out what the instructions say. If you don't want to follow them, just splice, dice and jumper as you see fit.

"Green wire from tach". "Didn't use the 121". "red power wire of my tach connected to 39" I'm not sure what you are doing. The HEI's I've used do not have their own wires. I assumed a GM HEI. I can't begin to figure out what you are doing. It's too risky for me to advise other than follow the instructions. You see what the instructions say, your ability to wire is low to medium, so follow the instructions or ad lib.

"I could still see someone using both wires though, just bc "the instructions said so".... This shows that you don't wish to follow the instructions for some reason.

The tach needs switched power.
The gauges need switched power.

1. 3A Pink goes to Positive terminal on HEI
2. 121 White goes to tach terminal on HEI
3. Gauge power, including gas and volt are supplied by 39 Pink. When ready, I will advise this hook up.

Thanks for the info- I think you are misjudging me since you cannot actually see what I have in front of me on the truck, so let me clarify:

1. 3A Pink goes to Positive terminal on HEI (this is wired as the instructions indicate)
2. 121 White goes to tach terminal on HEI
This wire would have been connected from the "tach" tab on the HEI, to the green wire of the tach itself. The 121 wire was not preconnected to the new fuse block in any way, it was basically like an extension cord between the HEI and the tach. Since the green wire of the tach was already long enough to reach the tab on the HEI, there was no need for the 121 wire. All it would do is add 2 more potential break points to the connection from the HEI to the tach.
3. the tach's main power wire (red) is connected to the harness' 39 wire (pink), as the instructions indicate.

I will figure out how best to hook up my voltmeter gauge from here, I was just looking for how others would/have done theirs. Thank you for your input, though.

I see what you mean. I didn't notice that 121 was just a piece of wire. Anyway, you could splice into 39 but a splice has to be done correctly and isn't the best for your immediate question. Assuming the aftermarket volt meter has stud terminals with nuts, you would run 39 to it using a crimped-on ring tongue terminal. Then another piece of 39, with another ring tongue placed onto the same voltmeter stud, to Tach. A jumper, in other words. Avoiding a splice.

Thank you!

This is known as daisy chain wiring.

Also, gauges have lights. Some are on a separate circuit as you know. So they can be controlled/dimmed. This is your 8 gray.

Yep, I am familiar with the daisy chaining from some other electrical applications, but did not know if that should be applied here, or, if I should incorporate some kind of junction block or similar.