Author Topic: 2007 Beaver Contessa Fuel Gauge Redux  (Read 5092 times)

William Mellman

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2007 Beaver Contessa Fuel Gauge Redux
« on: July 16, 2019, 03:08:09 AM »
Thanks to replies to my post searching for replacement gauge last fall, we found one at NW RV. Supply but it failed to solve the problem. At this point, we have tried replacing the sending unit, the ground wire in the system, the gauge (again) and are now trying another sending unit. Has anyone had the problem of the fuel gauge suddenly pegging above full all the time the ignition is on? It returns to empty when ignition is off, but does not drop as the fuel level drops. Would love to hear if anyone else has had or better yet- solved this problem.

Steve Huber Co-Admin

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Re: 2007 Beaver Contessa Fuel Gauge Redux
« Reply #1 on: July 16, 2019, 04:13:38 AM »
William,
If I remember correctly the sender in a full fuel tank outputs 12v to the guage and the voltage decreases as the fuel level drops. So that indicates your guage sees 12v whenever the ignition is on. I'd check the back of the guage for any loose wires that could be applying 12v. If none, disconnect the wire from the sending unit dverify it has 12v on it (do this with a partially full tank so the expected voltage is <12V). If it doesn't have 12v, you've probably got a faulty guage. If it has 12v, then you need to try to trace the wire to see if you can locate the short. Another more radical approach would be to cut the wire close to the sending unit and see if you have 12V at the sending unit (bad sending unit) or 12 v on the wire, disconnected at both ends (wire shorted to something.)
Not fun..
Steve

Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Gerald Farris

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Re: 2007 Beaver Contessa Fuel Gauge Redux
« Reply #2 on: July 16, 2019, 04:15:03 AM »
William,
A defective fuel gauge is normally a fairly straight forward repair if you spend a little time diagnosing the issue before you start throwing parts at it. The resistance in the tank unit increases as the fuel level increases. So, for a fuel gauge that pegs full, you check for power at the tank unit, if there is power at the dash gauge but not the tank unit, you have an open circuit. If you have an open circuit, you can look for the open (probably a green and fuzzy terminal at one of the connectors in the LF electrical bay), or just run another wire.

Gerald

William Mellman

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Re: 2007 Beaver Contessa Fuel Gauge Redux
« Reply #3 on: July 16, 2019, 09:35:03 PM »
We have spent so far 18 hours of tech time trying to diagnose the issue. First tests indicated
Appropriate voltage at sending unit and so was told gauge was bad. Tech must have measured voltage from the wrong terminal. Further testing revealed that ground wire might have been bad so ran new ground. Now have reliable 12.6V when testing the positive (ignition) terminal and the negative terminal on the sending unit with the ignition on. When we move the positive lead from the tester from the ignition terminal to the sending terminal while leaving the negative lead in place, the troubleshooting guide we got from a Monaco indicated that we should see between 0 and <9V depending on fuel level. The result with original sending unit was 0. The result with replacement sending unit was erratic between .5 and .7 V. Gauge was reading 7/8 tank due to calibrating to actual level. Meter should have read about 7.8V. When we slowly move the sending unit out of the tank ( simulating a drop in fuel level) the gauge immediately goes to full. Another interesting fact is that all wires from sending unit go to speedometer which seems to act as some kind of microprocessor that then relays the signals to all other gauges. Going to try and wire the fuel gauge directly from the sending unit to see if the speedometer might be the culprit. Can’t believe how mystifying this has turned out to be. Might have to go back to boating.

Steve Huber Co-Admin

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Re: 2007 Beaver Contessa Fuel Gauge Redux
« Reply #4 on: July 16, 2019, 11:32:59 PM »
William,
When you move sending unit out of tank is there a jumper between the sending unit housing and the tank? Not sure but it might require that as an added ground in order to get correct voltage. If no luck there, I would remove wire from sending unit to gauge and see if voltage remains at <1v or goes to correct voltage.
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

William Mellman

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Re: 2007 Beaver Contessa Fuel Gauge Redux
« Reply #5 on: July 17, 2019, 06:11:30 PM »
Thanks, Steve. We’ll try that next. I’ll keep you posted.

William Mellman

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Re: 2007 Beaver Contessa Fuel Gauge Redux
« Reply #6 on: July 23, 2019, 06:48:41 PM »
Latest update on fuel gauge: Sending unit construction is actually insulated from the tank itself when installed, so a jumper to add a ground to the tank didn't have any effect. BUT - 2nd new sending unit works when tested with meter. Empty sends 0 volts and full sends 9 volts. Gauge in coach moves just the opposite. As fuel level drops, gauge rises and the reverse. Only two possibilities remaining are that the new gauge is not compatible with the sending unit or the data being transmitted by the processor in the speedometer is faulty. We're considering a complete do-around with a simple aftermarket sending unit and compatible gauge mounted somewhere in the cockpit and just forget the whole thing since there doesn't seem to be any remaining resources to help solve the OEM installed equipment failure. If anyone can suggest such a resource, please share! Thanks to all who have tried. ;) 

Bill
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