Hi Group
We have a Europa Fuel sender on our mono. We had UMA build a nice fuel gauge
with
warning for the 9 positions. Range is .4 ohms empty and 190.7 ohms when full.
I never quite understood how the 9 positions worked.
Bill Daniels was kind enough to send me his old fuel gauge and sender. I figured
if mine failed I would have a spare. How easy! Well of course instead of
building
aeroplane tonight, I had to test it and make sure it was working well. NOT!!
Ended up it wouldn't read much below 1/2 tank and had some flakiness going
on on the way up to full, or down from full.
Can't have that. So managed to get it apart from the top and began
troubleshooting.
Think Applied Archaic Technology here, 1950s to be exact when you think of
old original computer core memory. Well if it was good enough to get Apollo
to the moon, it should be good enough to operate a Europoa Fuel gauge. But this
one failed?
OK here's how Europa designed it: they used special reed switches with what I
suspect
has a magnetic polarity, then they put a ferrite core on the outside of
the reed switch. Now when the float that has magnets passes by the reed switch
on the way to empty, it latches the reed switch to close the contacts and it
stays closed because the polarity of the ferrite core is opposite that of the
reed switch! Then when it passes on the way up to full, it demagnetizes the
ferrite
core and the switch opens. Each reed switch has a resistor across the terminals.
Thus when you start opening the reed switches, you start adding the
resistance together.
OK now what happened:
It appears that a rapid epoxy was used to hold the ferrite core to the glass
reed
switch. The position of the ferrite core is incredibly critical. Ends up the
rapid epoxy is not a good choice as it failed and a number of them slid down
due to gravity and stopped latching.
I was able to tune them using a very mild magnet to get position optimized where
they would easily latch and unlatch. Then when using the float magnets, they
work really well. Instead of rapid epoxy, I used some non stink silicone to hold
cores in position.
Bottom line it now works great and I figured out how the thing works and I now
have a spare.
It seems unless who ever fabricated the fuel sender changed adhesive, they are
at risk to go flaky.
Figured i would share.
Europa figured into the sender the shape of the fuel tank so they position the
reed switches at 1/8 tank increments. When doing the repair I could see see the
different spacing.
Ron P.
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