A couple of things about the fuel gauge:
One, it will work at 12 volts and there are reasons to think it may be ok to do that for a long time. Your fuel gauge cares more about current than voltage. I've not heard of a fuel gauge failing from being run on 12 volts, but I do know things can change inside that gauge. (see two, below)
Two, operating it at 12 volts may alter the
permanent magnet in the gauge. Please see the image below and the light blue pointer. Look closely and you'll be able to see an hourglass-shaped piece of thin metal which pivots along with the needle. Doubling the voltage going through the 2 electromagnet coils you see (one copper colored and one black)
will increase the electromagnetic field present in your gauge and this means the permanent magnet (the hourglass-shaped piece of metal) will consequently have its magnetic field increased. When that occurs, the gauge will now reflect a fuel level
lower than true fuel level
if a lower voltage is then applied to the gauge. Any permanent magnet subjected to a magnetic field which is stronger than that permanent magnet's natural field will have its magnetic field increased. What I just said can be summed up as: you can go through this door, but you can't go back. Once the permanent magnetic field is increased, the gauge will forever read differently, especially if the voltage to it is reduced.
How long does the change in magnetism take? Opinions differ. There are too many variables in the case of this particular gauge to pin this down and no studies have been done to my knowledge. But when it does occur ("it" meaning the change in magnetism of your permanent magnet), your gauge will not work correctly unless it continues to receive the higher voltage. If later subjected to a lower voltage (example you changed from 6 v to 12 v and now you want to use a voltage reducer), the gauge may read
all fuel levels as being
lower than they actually are.
Bottom line in my opinion: if you've been running your fuel gauge at 12 volts, just keep doing so. Lowering that voltage now will possibly make your gauge inaccurate. If you're converting from 6 volts to 12 volts, then I'd use a voltage converter,
but I'd get one that's adjustable. Then, I'd fill my fuel tank, connect the converter and adjust it until the fuel gauge reads F. At that point, other readings should be as accurate as the AD gauge can be (and it can do a very decent job if you have a good sender unit and an adjustable circuit). And the neat thing is if your fuel gauge ever starts reading too high or too low...you can adjust it as needed. If you need more info on an adjustable converter, please send a PM or an email to
[email protected] The one I make can be seen below.
