Fuel Gauge Reads Backwards.

Anyone know what causes a fuel gauge to read full when empty and empty when full? I tried swaping the positive and neg wires on it but that was not the problem.

Pete,

Thanks for chiming in. The gauge is in my buddies Alpina boat. I'm installing a Perfect Pass for him and he asked if I knew what is up with the backwards reading fuel gauge. So I'm looking in to it for him.

The Alpina is a 1999 powered by a Mercruiser 5.7 MPI just like many Malibu boats of the same vintage. It's a pretty "plane Jane" boat with really basic equipment.

He told me the gauage reads empty when full and full when empty. He also said it moves steadily and consistantly as the tank empties like it's working properly but just backwards. I thought it seemed like something is connected backwards.

Of course he left me the boat with 1/2 a tank so it's hard to know if I have corrected the problem. The gauge at the dash has a pink wire on one side a blue wire on the other and black in the center. I tried swaping the wires around but the only way the gauge works at all is with the wires the way I found them.

I was suspecting the problem was at the tank from the start but thought I would start with the easiest part to get to first. I can't find much information about these boats but I thought some hear might have some ideas.

Try to maintain 1/2 tank at all times

Seriously, the problem is on the sender end.

This is what I found. I pulled the sender unit out of the tank and sure enough when the float arm was up it made the gauge read empty and full when down.

I decided to take the sender apart and reasemble it with the mechanism inverted. Put the sender back in the tank reconnected the wires and the gauge reads correctly now.

Couldn't you have just run the boat upside down?

65 'cuda wrote: Couldn't you have just run the boat upside down?

I thought about it but I would have had to take the tower off to get the boat on the trailer then. Although that probably would have been easier than all the floor disasembly/reasembly I had to do to get to the gas tank.

On this brendella/Alpina the tank is in the floor right about where the dash is. To get at it you have to pull a floor panel, to pull the floor panel you have to remove the pylon, to pull the pylon you have to pull the side floor panels, to pull the side panels you have to take out all the seats. At least with all that out of the boat it was real easy to run the wires for the perfect pass. No wire snake needed.