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Discussion Starter · #1 ·
I recently scored a set of '65 SS gauges off of ebay. They are guaranteed to work and I want to test them as soon as they arrive. In a past post I have copied and saved I got info on how to test the temp gauge so I'm set there.

Can anyone give me a run down how I could bench test the fuel gauge and amp gauge? I have a decent multitester and the variable resistor I bought to test the temp gauge (0-500 ohms range if I recall correctly).

The oil pressure gauge is a mechanical device so I'll have to hook it up to the oil pressure line on my old truck to test it. Getting to the line on my truck will be much easier than getting to the line in my Chevelle.
 

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Rich, I’ve dropped my tank and I’m replacing the trunk pan so it’ll be out for the next couple of weeks. I have the sending unit out of the tank and it works if you would like to use it for your test. Darren - Omaha
 

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Thanks for the offer Darren. I have the sending unit out of my wagon I can test with, assuming it works properly anyway. I'll probably be replacing it anyway as it is fairly dirty, the sock is toast and I want to try to install a larger feeding tube anyway.

It just occurred to me: all the gauges on my coupe work fine. Couldn't I just take loose all the connections at the gauges, make temporary harnesses that are routed to the new gauge cluster, ground the new cluster to the car and see if the readings on the new gauges match the readings on the set in my coupe?
 

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That sounds like a lot of work, I don’t know if I would completely disassemble something that’s working to test something that might not. I think I would just hook them up in the car you are going to install them in permanently and trouble shoot individual problems as they arise, if there even are any. You mentioned they are guaranteed to work. I think you’ll know if they’re working or not before any damage occurs to the motor. * I did not take into account that the car you are installing the gauges into may not even have a motor?? If that’s the case your plan is a good one, so you can return them in a timely fashion if need be.
 

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Discussion Starter · #6 ·
Originally posted by 70 nialator:
That sounds like a lot of work, I don’t know if I would completely disassemble something that’s working to test something that might not. I think I would just hook them up in the car you are going to install them in permanently and trouble shoot individual problems as they arise, if there even are any. You mentioned they are guaranteed to work. I think you’ll know if they’re working or not before any damage occurs to the motor. * I did not take into account that the car you are installing the gauges into may not even have a motor?? If that’s the case your plan is a good one, so you can return them in a timely fashion if need be.
Exactly, the gauges are for the wagon project and it is a long way from being a complete vehicle and is completely disassembled at the moment and will be so for years to come.

I'm not suggesting disassembling the gauges in my coupe, just taking the wires loose from the back of each gauge and routing wires from the plug to the new gauges which would be propped up on the floor of the car temporarily.

Testing the fuel gauge would be simple enough. If the tank is half full according to the gauge in the coupe, turn off the car, disconnect the fuel gauge wire, route temporary wires to the gauge on the new set of gauges, ground the new gauge cluster and turn on the key to see if it registers half a tank.

I would assume the same could be done for the amp gauge. I already have procedures for testing the temp gauge from some past threads. The oil pressure gauges is easy to test too, just hook it up to the oil pressure line temporarily and start the engine to see if it registers pressure and if it does so accurately.

The only one that makes me nervous is testing the amp gauge since if I short circuit something I suspect I could do some serious damage to something or other. I'd really like to find a way to bench test that gauge if I can.
 

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It’s been a long time…. But I think this will work, if you have 2 wires with alligator clips at each end, about 5 foot each & an inline fuse in one of them just to be safe. Run one from the starter main B+ to one post of the gauge. Run the other from the alternator output post and the remaining post of the gauge. Then turn on the head lights and blower motor to check the gauge for charge / discharge.
Like I said it’s been a while so if anyone can validate my theory or correct it please do so.
 

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You can test the amp gauge with a 1.5 V battery, AAA if you have it AA or D will work the smaller the battery the better, the smaller battery will supply less current. Connect a wire to one of the gauge terminals, then touch the battery + to the other terminal and the wire to the battery -the gauge pointer will peg full scale. Reverse the battery, the gauge will peg the other direction. The D battery will really slam the movement against the mechanical limit the AAA will hit the limit but not hard. A battery that is somewhat discharged will probably work better. NiCads or Ni-MH will also work.
 

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For the fuel gauge I'd use the sending unit and "mock it up" just like in the schematic. That way you're testing your gauge and sender together and won't have to wonder if it's gonna work in the tank.

I don't have a schematic handy, but I think it's +12v to one side of the gauge, the other side of the gauge connected to the sender wire, the sender grounded to battery negative to complete the circuit. The sender is a variable resistor to ground (or battery negative). The gauge should track the movement of the float.

I wouldn't even bother pulling the battery from the car to do this. Just pick up any easily accessible 12V source and ground it wherever you want.
 

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If testing the fuel gauge be sure to ground the gauge. The applied voltage has two paths one gauge winding grounds at the gauge, the second gauge winding grounds through the tank sender. This scheme gives the same level indication, for any given sender resistance, regardless of the applied voltage. The temp gauge works the same way.
 
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