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Cantedvalve

Gauges not working...

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My oil, water, and fuel gauges don’t work.  I checked the wires from senders to dash, no breaks.  I replaced the voltage regulator today with a solid state... no change.  I checked voltage going to the voltage regulator, and I have 12V, which seems wrong given the resistor wire.  I checked the resistance of the gauges and I got no resistance. All three showed the same on the meter.

So... what the hell?  What am I missing?

 

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I'll bet you recently changed the circuit card, or re-set the gauges in the dash cluster.  When doing this, one of the gauges is inadvertently having one of its posts touch the metal housing, shorting all of the gauges.  You can test proper installation by measuring resistance from each post to chassis ground: you should not see 0-1 ohms on any post.  If you do, that's the culprit.  Loosen the two retaining nuts, and move the gauge around.  With a circuit card, you cannot see the posts hitting the dash housing due to the card and the insulating pad. 

Why do you see 12V even though it is a resistor wire?  You have no current flowing through the system, so you only have voltage and no current to "resist".  You should see 12-14 ohms on each gauge, going from post to post.  With everything hooked up, though, you may not see this.  Best to disconnect the button plugs on the CVR while making this resistance measurement.  Even then, there is a trace that connects all three gauges to the output of the CVR.  If one of those posts is grounded (inadvertently), then all three will be grounded. 

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I have the whole cluster out of the car (again).  When I individually test each gauge, I get zero ohms.  I took the card off, and I still get zero ohms.  I took the gauges out of the cluster, and I still get zero ohms.

I got the 12V reading (I should say >10V) with the key on, and the cluster out.

So..........

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Okay, start with the oil gauge.  I have it completely isolated.  Post to post I get zero ohms.  There is zero chance that it is grounding out.  I get the same result on the fuel gauge and temp gauge.

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I have a hard time believing that I cooked 3 gauges without hooking them up.  They would have to be shorting straight to ground, and the ground wires havent even been hooked up yet (the harness isnt installed).  I've just been trying to test them from inside the car.

So I took my oil pressure gauge and ran a 1.5V AA battery across the terminals.  Low and behold, the needle moved about around 1/4 to 1/3 across the gauge.  Now, I am not an expert by any stretch... but that seems right?  If it is on a 5V scale, and assuming that its somewhat linear, that should be about where it ends up.  Maybe my multimeter is bad?

On the resistor wire, are you saying that 12V is normal at this point?  Key on, wire disconnected, measuring with a multimeter.

All I know is I dont want to put this cluster (pun intended) back in just to have to take it out again.

 

 

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Amazing what happens when you dont have crap tools.  Took the oil pressure gauge to our maintenance department and used one of their nice Fluke digital meters... 12.6 ohms.

I think I checked everything else.  Ground wires are good and solid.  It could be that my car is in a 30* garage and needs more than a couple seconds to heat up the element to make it move.  I am going to put everything back tonight and see if it works.  Might have to pull the car outside to run it.

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Have been there a few times. First was the gauge post shorting to the metal housing. More recently the after market CVR failed. I refitted the original 50 year old CVR and that fixed it. Good luck mate.

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Yeah, I started down that road before. Problem was, the gauge panel didn’t fit my car... almost all if not all of the aftermarket gauge panels are made for 1969 cars, despite being marketed as 69/70 parts, and will not work with a 1969 unless you replace the steering column.  I did run across a set of aftermarket gauges the other day that would fit the stock dash... just don’t want to pay for them right now.

Got my parking lights in today along with the quarter panel lights.  Missing a taillight bulb.

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