Fuel guage has stopped working

tjbrace

tjbrace

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In an attempt to fix it I have removed the guage and the Yanmar engine control panel. The sensor is still in the tank so I am wondering how to test the removed parts at home.
I have a multimeter but it doesn’t measure capacitance and I am presuming the sensor uses capcitance. There are 2 wires from the guage to the sensor, the brown connects to a terminal marked G and the blue connects to the negative terminal. There is a positive feed terminal and also a feed and return for a lamp.
Any ideas how to test it?
 
tjbrace said:
I have a multimeter but it doesn’t measure capacitance and I am presuming the sensor uses capcitance.
Click to expand...

Gauges usually work on variable resistance, not capacitance. The sender is usually 0-180 ohms, so if you connect a small potentiometer across the sender connections you should be able to see whether adjusting the pot gives a changing reading on the gauge.
 
Many thanks PVB. Spot on, just been back to the boat and measured the sensor, 156 ohms, fullish tank. I shall buy myself a potentiometer tomorrow - Rapid Electronics beckons.
 
PVB, has already pointed you in the right direction. I also have a Yanmar control panel but the gauge is actually separate from the panel and both the gauge and the sender are made by VDO. The most common fault is the sender goes open circuit and the gauge shows permanently full! (VDO european senders/gauges show full for open circuit and American senders/gauges show empty!!).
After you have tested with your "pot" you will know if it is the gauge or the sender which is faulty; the most common fault is the sender wire coil "wearing" out and going open circuit or developing a poor contact with the "slider". Once I had the slider work loose on its spindle and was able too repair it, but mostly the coils/sliders after a number of years become "rusty" and gunged up and whilst it is out of the tank you may just as well replace it. A new sender will cost you about 60 euros from a local chandlery but no doubt you can find them cheaper on line. Before you bin the old sender (if it is that) measure the length of the sender and cut/adjust the new one to the same length - then it should be calibrated and read the same as before.

Alan.
 
Thanks Alan, my guage is also separate from the Yanmar panel but was fed from the connecting loom. I removed both as my first impression was ‘no power’ to the guage (indicator doesn’t move). Ultimately, I would like to test all panel parts before I reinstall them. Also need to glue back the broken panel corners.
I know the sensor isn’t open circuit as I measured 156 ohms across it yesterday. It’s good to have the info you gave though.
They are also VDO.
T.
 
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I contacted VDO technical help and they were really... helpful, gave me the details of the resistance reading for empty and full that it should be. If you need I can dig through my info when I get home from work.
 
The potentiometer test was a success. It showed the guage responding correctly.
Unfortunately I was not able to setup a test rig for the control panel so that will have to be reconnected on the boat today and the bad connection traced there.
Thanks for your help. T.
 
If the sender is broken consider replacing it with a WEMA unit....just google them. Used a lot in industry to measure tank depths, Also note when replacing the screw location is not symmetrical in circumference. Nik
 
My fuel tank had the type of sender with a float on a long lever. It failed progressively until ultimately gave no reading at all. I replaced it with an Osculati sender similar to this https://www.ebay.co.uk/p/Osculati-2...Fuel-Tank-Level-Sender-240-30-Ohm/16005167185 that I was advised was very reliable in all sorts of fluids. I had to remove the tank to fit it, taking the opportunity for a thorough clean and to replace the outlet fittings. The gauge has been accurate and reliable since. The appropriate length needs to be selected for the depth of tank.
 
Replaced our swinging arm one that failed on one tank with another similar. Original had a wire bridging the fixed vertical part to the swing arm join and that failed at the micro crimp terminal reading full at the guage. ayard fitted new one but dedicated blue peter sticky back plastic man might have replaced the wire and had another years use.
 
Thanks to all for your help.
Guage and sensor are fine, problem was their positive feed, spliced into the control panel loom, had a bad connection. So it is all back in place and working. (For now)
 
Pleased you got it fixed - at no cost!! I just wanted to add a bit to this subject in case, in the future, somebody is searching for some info in this thread on Yanmar Type-B control panels:

I have just finished servicing my engine (usual stuff) and when switching on the engine I found there was no alarm buzzer and only the "charge" light was coming on. I assumed it was the buzzer and removed the small PCB with LEDs from behind the (Yanmar Type-B) panel; but when I tested it on the bench (with a 12v supply) all the lights and the buzzer were working fine. But a few notes below to help anyone else when fault finding:
1. The charge alarm light is not wired through the buzzer (so does not cause an audible alarm)
2. The water temp alarm is normally open and goes to earth when temp it too high (obvious really but fooled me for a few minutes!!); so lamp does not come on when the panel is set to "on" (can be tested by earthing the spade connector on the water temp sensor).
3. The oil pressure alarm is normally earth (buzzer sounds) and goes open when there is oil pressure
So, when you put the panel to "on" the only connection that causes the buzzer to sound is the oil pressure. (I cured my problem by giving all the loom connectors and the oil pressure connection a spray with contact cleaner and then making and breaking the connectors a few time - a known problem with Yanmars is poor quality loom connectors.

Hope that may help someone in the future and save them some time!!

Alan.
 
alan said:
1. The charge alarm light is not wired through the buzzer (so does not cause an audible alarm)

Alan.
Click to expand...

That's useful to know. I had always assumed that the buzzing when I turn the ignition on and off was the oil pressure because of the delay after a filter change and had assumed that the buzzer would sound if the engine ever overheated, which it hasn't, but I did wonder whether the buzzer would sound if the alternator failed at higher revs but clearly not. My system also has the saildrive water ingress sensor wired through the buzzer which means that sometimes the buzzer comes on and then doesn't go off when engine starts and oil pressure rises.

Richard
 
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