Gauges recommendation

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mr 88

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Check , remove bolt that holds the wire on top of the sending unit ,clean wire and bolt that holds wire on top of the sending unit . That is a common issue with fuel gauges .
 
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LWD

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nola mike said:
Hmm, looks like your gauge is reading 2v too high. Next step is to measure the voltage at the gauge. I'd probably check with the wiring on, and if the DVM is high I'd disconnect the leads from the voltmeter and remeasure. Lastly, I'd run a ground directly from the battery. Set the DVM to DC volts and measure between that jumper and the ground wire(s) at the helm--there shouldn't be any voltage between them. Do that KO/and engine running.
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This is our 4th of July family week, it's being crazy around here. But it's so much nicer than on the 4th weekend, don't have to deal with the boat ramps and lake traffic.

I tested the voltage at the gauge leads connected. Key off - 0.00 volts, Key on the voltage fluctuates between 0.00 and 0.01.

Leads disconnected from volt gauge. Key off - 0 volts. Key on - 12.28 volts. Engine running, tops out at 14.16 volts.

I think I understand the jumper part, I ran a jumper from the negative side of the battery and measured the DVM + probe from the jumper, and the DVM - probe to the ground on the volt gauge. With key on, the DVM again fluctuates between 0.00 and 0.01. Engine running, the DVM measures 0.03 eventually settling down to 0.00 after running about 45 seconds. The volt gauge at the helm still reads above 16 volts.

Also, I cleaned the wire connectors, but they really didn't need it. They all look very clean, no sign of any corrosion.
 
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LWD

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mr 88 said:
Check , remove bolt that holds the wire on top of the sending unit ,clean wire and bolt that holds wire on top of the sending unit . That is a common issue with fuel gauges .
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I'll get around to checking this next week, after our company leaves. Appreciate the suggestion. (y)
 
dingbat

dingbat

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nola mike said:
Lastly, I'd run a ground directly from the battery. Set the DVM to DC volts and measure between that jumper and the ground wire(s) at the helm--there shouldn't be any voltage between them.
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And the purpose of looking for voltage between battery ground and the ground on gauge?

I could see checking the resistance (ohms) but voltage between grounds?
 
nola mike

nola mike

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dingbat said:
And the purpose of looking for voltage between battery ground and the ground on gauge?

I could see checking the resistance (ohms) but voltage between grounds?
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To make sure that there isn't a short to power on the ground wire causing the high readings.
Done on the positive side it's a voltage drop test. Picks up issues particularly under load that a resistance test will miss (small static resistance that becomes significant with high current passing through).
 
ratdude747

ratdude747

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LWD said:
This is our 4th of July family week, it's being crazy around here. But it's so much nicer than on the 4th weekend, don't have to deal with the boat ramps and lake traffic.

I tested the voltage at the gauge leads connected. Key off - 0.00 volts, Key on the voltage fluctuates between 0.00 and 0.01.

Leads disconnected from volt gauge. Key off - 0 volts. Key on - 12.28 volts. Engine running, tops out at 14.16 volts.

I think I understand the jumper part, I ran a jumper from the negative side of the battery and measured the DVM + probe from the jumper, and the DVM - probe to the ground on the volt gauge. With key on, the DVM again fluctuates between 0.00 and 0.01. Engine running, the DVM measures 0.03 eventually settling down to 0.00 after running about 45 seconds. The volt gauge at the helm still reads above 16 volts.

Also, I cleaned the wire connectors, but they really didn't need it. They all look very clean, no sign of any corrosion.
Click to expand...
With the volt gauge disconnected do/did the other gauges start working?

If so, the volt gauge is shorted (faulty) and is overloading the instrument cluster wiring.

If not, there is likely a marginal connection in the power/ground feeding the instrument cluster. Analog gauges (especially voltmeters) draw an appreciable amount of current but digital volt meters do not. As a result, without a load, it's possible to see full voltage through a high-resistance connection (as voltage drop is a factor of resistance and current, more current means more drop).
 
nola mike

nola mike

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ratdude747 said:
With the volt gauge disconnected do/did the other gauges start working?

If so, the volt gauge is shorted (faulty) and is overloading the instrument cluster wiring.

If not, there is likely a marginal connection in the power/ground feeding the instrument cluster. Analog gauges (especially voltmeters) draw an appreciable amount of current but digital volt meters do not. As a result, without a load, it's possible to see full voltage through a high-resistance connection (as voltage drop is a factor of resistance and current, more current means more drop).
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Not true. Voltmeters are designed to draw negligible current. Agree that if the voltmeter is faulty then it could be drawing some current and affecting the rest of the circuit. Key on zero volts across it would mean a dead short though. And OP had the voltmeter reading 14+ previously.
 
dingbat

dingbat

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nola mike said:
Picks up issues particularly under load that a resistance test will miss (small static resistance that becomes significant with high current passing through).
Click to expand...
Not buying it….

A voltmeter uses a high resistance wire coil to create a stable, magnetic field unaffected by current. The interaction between the magnetic field and a permanent magnet within the gauge causes a pointer (needle) to deflect.

In this case, testing ground resistance to determine the integrity of the ground are appropriate since ground has a direct effect on the reading.

In theory, ground resistance should be 0 ohms but that is rarely obtained. Our equipment is super sensitive to ground disturbance so we require 5 ohms or less.
 
ratdude747

ratdude747

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nola mike said:
Not true. Voltmeters are designed to draw negligible current. Agree that if the voltmeter is faulty then it could be drawing some current and affecting the rest of the circuit. Key on zero volts across it would mean a dead short though. And OP had the voltmeter reading 14+ previously.
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Valid point... if the voltage is coming back to normal with just the volt gauge disconnected (other gauges still connected) and swinging from 0 to full system voltage, then that points to the fault being an internally shorted volt gauge or some other short that was corrected by disconnecting said gauge.

That said, an analog gauge will be lower impedance than a digital multimeter's voltage measurement (in a "normal" high-impedance mode), if nothing else because the gauge sources all power from the sensing connection (at least every marine volt gauge I've ever seen), while the multimeter has it's own battery/power source that powers most of the meter circuitry. Not a huge amount (as it is designed to be "negligible" in most cases), but enough that in a very poor connection situation, I could see it making some difference if one only had a volt gauge or had disconnected all gauges (in which case, the same issue would be multiplied once for each gauge removed from circuit). As dramatic as a more substantial load (motor, solenoid, etc.)? No. But the principle still applies.
 
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LWD

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nola mike said:
LWD said:
I tested the voltage at the gauge leads connected. Key off - 0.00 volts, Key on the voltage fluctuates between 0.00 and 0.01.
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That's weird. Key on should have 12v there.
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I'm not sure what happened there in my original comment about the voltage, so I redid the test with the Key on, and it is reading 12v. I must have messed that one up, sorry about that, it's not right for me to be asking for help and I'm giving bad info. :(

ratdude747 said:
With the volt gauge disconnected do/did the other gauges start working?
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The other gauges (fuel and tach) did not start working normally. Of course I had to start the engine to check the tach, but it's been just flat out wonky since last year, and it's still wonky with this test. With the tach, I've tried moving the cylinder selector switch on the back several times last year, it didn't help.
 
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nola mike

nola mike

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What exactly is the fuel gauge doing?
So engine running you get 14v on your voltmeter with the leads connected, but 16 volts on your gauge?
Next test: Ground the sender wire from your fuel gauge. Should peg full. Disconnect sender wire. Should read empty.
 
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LWD

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I consider the fuel gauge to be a minor issue, but nonetheless I notice it. I trust the fuel gauge in the key on position, but key off doesn't drop below the "E" line like it used to. On to the next test.

That is correct on the voltmeter test with engine running.
 
nola mike

nola mike

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Alright, sounds like you officially have a bad volt gauge. Fuel gauge sounds OK, wouldn't worry about where it settles key off.
Last is the tach. "Wonky" might need a better description. First step is cleaning the connection at the coil (you said already clean at the helm) or disconnect the gray wire altogether and run a jumper directly to the tach to see if it dewonkifies it.
 
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