MGL Avionics User Forum

HI
Could use some help here. I have been trying to get my fuel levels to read out on the EFIS> I have the 10.5 Challenger. I have 4 tanks. Two on the RDAC one and two on the RDAC two. I have replaced all the float sender units with Stewart Warner floats. They all work but the right side inboard. It reads Zero. The raw data reading is 3908. The tank has about 12 gallons of fuel in it. The left inboard tank has about the same amount of fuel and its raw reading is about 1200. This is all on a Zenith CH801. I checked the floats with an ohm meter before installation. They all read around 35 to 245 ohms. Do I have a wiring problem. I checked with a volt meter and got 5 volts on the sense wire (middle wire). the other senders all show about .6 volts. I thought I was missing the ground so I wired up a temporary jumper to a bolt on the wing. still nothing. Any Ideas appreciated on how to trouble shoot this.

Your fuel level input reading the high number (around 3900) seems to have nothing connected to it. This is about what you get if the input only sees the pull-up resistor in the RDAC (enabled by dipswitch).

To test the input - simply use a piece of wire to short the input to ground - it should then read "0".

Rainier

Thanks Ranier

I did the ground thing and found that I was not getting a good ground. These Stewart Warner floats do not have a dedicated ground screw like the VDO ones did. I was relying on the mounting screws for a ground. 3 of them worked fine but there is always one in the crowd as they say. I finally got it to ground, but I'm going to try and solder a wire on the top and put it with the ground wire to make sure its getting good ground and completes the path. Thanks for getting me going in right direction.