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I bought a 69 a while back that had no gauge cluster. I bought one used off Ebay, the wrong one obviously, My truck evidently was equiped with idiot light and cluster I bought was for gauges.
I notice on forums comments saying this is a super difficult to swap, not worth all the trouble etc. However after plugging it in most of it works perfect. I did change oil sending unit
to the correct style and have a mustang tank swap so fuel gauge and oil pressure and lights works great. The temp gauge and alt is not working which I will be figuring out soon
because I want to change to 3g alternator etc. So my questioin is Why do i see comments saying you cant do this , you have to change the entire wiring harness to the correct cluster style ?
So far it seems almost plug and go, or am I missing something ? Is it slowly melting wires or gonna be a ball of fire any minute? Anyway so far I have no problems.
I went from idiot lights to gauges and I didn’t have any problems I had to run a couple of wires for the alternator gauge BUT that’s was it everything else worked fines.
Last edited by DCrusher; Apr 27, 2026 at 09:38 AM.
I agree with dropping the Amp Gauge and going with a Volt Gauge. There is someone that will convert your Amp Gauge and make it a Voltage Gauge. this is the site for converting the Gauge https://www.rccinnovations.com/index...=menu-volt-all
Here is a diagram from a 71 manual your wire colors may be different. Wiring the amp gauge in should be a simple matter. You may find the basic wiring already exists in the harness.
I would keep the AMP/ALT gauge it gives you a better read on your electrical system than a voltmeter. A voltmeter only reads system voltage with no regard to the load. You can be drawing more current than the system can support and still have a normal voltage reading. That's why most large aircraft have both. Also if you look at the wiring for just a charge indicator light you will see a 15 ohm resistor wire paired with the light it is there to provide exciter voltage to the ALT. if the bulb burns out. That wire usually doesn't appear on the regular wiring diagrams.
The compilation for the AMP meter with a 3G conversion will be making your own shunt, for 130 amps.
To my knowledge , no one has done this on this forum site.
Also, a needle width of meter movement would be around 10 amps. I not sure you would notice a 5 amp discharge rate while driving down the road.
Jim
Last edited by JimsRebel; Apr 29, 2026 at 10:11 AM.
Perhaps the inconsistencies you’ve seen over the years, involved different year trucks and different gauge versions as well.
For example, a 69 and 70 might be very close to working together, where a 68 and a 72 may be less compatible.
Also, different owners comfort levels with wiring vary greatly!
I’m a big fan of ammeters, that work!!
I like both amp and volt even better.
But I’ve never been a fan of either the later shunted type, or the earlier direct-reading type. Very little experience with aftermarket models.
That said, if I had the cluster out now, and was planning a 3G swap later, I’d be converting to a voltmeter while it was convenient.
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