Fuel Gauge Maladies......

[khamsin190]

Hello,
I've owned a 1965 190c for about a year now and so far it has been lovely except in one rather irritaing area. The fuel guage, rather than showing the acutal amount of fuel, only begins to drop when I estimate there is about a quater of the tank left and even then fluctuates wildly with no ryhme or reason. This has once left me on the side of the road without fuel and is really bothering me as of late. I think it may be a short, but any ideas would be appreciated.

[Don350SDL]

In general, fuel sensors work on lower resistance for a full tank, higher resistance for empty. To indicate too full, you'd need a low-grade short (one that has resistance, not just a dead short of 0 ohms).

First test the gauge with a resistance substitution block. Or use a variable potentiometer, around 100-150 ohms should be about right.

Then use an ohmmeter to test the sensor. I'd bet that's the problem

It's unlikely to be the wiring. The service manual should have the specs for the sensor (Ohms full & empty)

Don