Well I'm almost ready to put the cluster back in, but just to make sure everything was kosher (it's not), I tested the gauges with mixed results.

What I did was apply 3-4 volts to the fuel and temp gauges. The fuel gauge worked fine, if quite slowly (I figure this is to be expected?), but the temp gauge wouldn't even register. I assume it got cooked somehow.

And for what I assume is a voltage gauge (as opposed to an ammeter), I put 13 volts to it and all the needle did was move slightly to the left of it's resting point in the middle. The power supply only puts out 1 amp max, so could that explain the slow/inoperable gauges?

Any hints or tips you guys can give me here?

Update: Okay well the temp gauge is toasted. The little wire coil inside got cooked somehow (I'm guessing heat from one of the two engine fires the car's had or it got shorted at the same time the pins on the PCB got bent up and broken). Either way, dead soldier. I'd rather have it repaired then replace it with an Autometer, since I HATE seeing a dead gauge and then a working aftermarket gauge right next to it, though I'm sure an Autometer would be much more accurate.

Any thoughts on how much a repair would cost?

Now the more I look at the car's wiring, the more it looks like the alternator gauge IS an ammeter instead of a volt meter, given the way the wire comes off the alt's post, to the gauge, then from the gauge to the battery. Can anyone verify that for me?

Here's a pic of the type of cluster it's from:

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Never apply a direct voltage to an ammeter. Ammeters measure flow of current. By applying voltage you are shorting the in and out terminals and possibly burn it. To check that it is still working check for continuity.
And yes, your alternator gauge is an ammeter

You probalby toasted the fuel gauge by applying more voltage than it was capable of handling.

I don't think you can easily find someone to repair these items, again your best bet will be the JY for a cluster off a similar type.

Good luck

Rafa

Well I know the fuel gauge and temp gauge operate off of a max of 5 volts, so I tested both with 3 volts, per the article in Mopar Muscle on testing gauges. Fuel gauge tested okay, but the temp gauge was dead.

For the ammeter, I still got continuity; but with a 60A alternator, shouldn't the needle move all the way to the right?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG



Know how they always build a better idiot? That's me

Only if you are actually drawing 60A from the alternator. If you have a 60A alternator, think of it as 60A of reserve current, it doesnt always put out 60A, you just draw from the reserve as needed, with 60A being the maximum.

So the more current I'm drawing, the farther to the right the needle would be? Or does it try to stay centered as long as the alt can handle the current?

Dang, maybe I should just get a voltmeter in there too...

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG



Know how they always build a better idiot? That's me

If you had the alternator disconnected, and you turned on your lights etc to start putting on electrical load, the meter would move to the left, and read say -5a for example. If you have your alternator connected with the same load as before, in theory it should move to the right +5a. Think of the center as a 0 point, no current flow.

Imho, in a car an ammeter isn't of much use, a voltmeter provides more useful information. A voltmeter on the other hand, tells you how much voltage everything is getting. You know that if the voltage drops below a certain point you need to look into things. but if your drawing X amps, what use is that information?

My thought's exactly. I'm thinking I'll go ahead and ditch the connection to the ammeter, and since this Autometer triple gauge I'll be installing has a voltmeter, I'll rely on that.

In this case since it's a dual field system, can I still just take a big fat wire straight from the alternator's post to the battery?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG



Know how they always build a better idiot? That's me

Don't ditch anything, if you want to disconnect the ammeter, you have to connect the two wires together. The way I did it was just put a screw through the ring terminals with a nut on the back and tape it up.

That way you don't have to take a wire straight from alternator to battery, just keep using the stock setup as normal. I'm assuming you have a stock alternator.

Yeah, well actually a 60A replacement. I would suspect the factory ammeter can handle it though. Or was it only made for a max of 30A?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG



Know how they always build a better idiot? That's me

I'd keep the ammeter hooked up. You can add the voltmeter anyway, each gauge will operate independently of each other.
Normally the ammeter is wired so it only shows the current going to or from the battery. When's the last time you charged a battery at 30 amps or even 60 amps?
If your battery is charging at 3 amps current and your lights, radio, electric fan, etc. is drawing 25 amps the ammeter is only carrying and showing the 3 amps to the battery.