I bought a VDO 301-105 Fuel gauge for my O'day 35. This is described as a 240-33 Ohm Fuel Gauge. The fuel gauge in the tank works great, except that you can't see it.
This is a Mohler mechanical gauge that has the sending capsule built in. When empty it reads 247 Ohms, and when full, it reads 35. - Close enuf... I connected it as follows: +12V to the Instrument circuit breaker (RED), Sender "S" (PINK) to the sender, and a YELLOW wire from the other side of the sender to the ground bus. Simple eh?
Well the needle is PEGGED FULL 100% of the time.
OK, so I suspected the sender might be doing something unseemly, so I purchased a new sender, and crawled into the lazerette, and installed while practicing my yoga positions... same thing.. FULL 100% of the time.
So, I pulled the sender and tested it by moving the arm up and down. Still, FULL 100% of the time.
I then pulled the gauge and tried an ohm meter on the terminals. All the way up (full) read 30 Ohms, and all the way down (empty) read 246 Ohms...
Must be a bad gauge, I figured.. So I bought another new one. SAME RESULT!!!