Help with some electrical glitches

[Steve Barnes]

My hobbs just turned 1000 hours last week and my Vans oil temp is failing. Easy fix, I'll just get a new one.

The one that really perplexing is my Vans fuel gauges. This last year the gauges started to intermintentley not work. Some times they would both would work. Some times one only would work and some times both would not work. I cleaned all my major engine and battery grounds and my engine starts easier and the gauges worked fine (battery is grounded to a longeron way in back because heavy engine). I had a hot start that took several tries the other day which sometimes happens on a hot day. When the engine started both fuel gauges were not working. I have started the engine several times since then without running the battery down and the fuel gauges work fine. Do you think I need new fuel gauges or could it be another problem?

Thank you for your help. Steve

[F1Boss]

Hey Steve:

I always wondered about the starter loads going thru the airframe longerons in the Rockets (smallish cross section, and lots of connections along the way), so I started adding an additional ground wire thru the center fuselage. As I recall, it was a #8 or a #6, but not a full sized wire like the hot lead (#0 welding cable).

I have no data to provide as to whether this was actually required, but I reasoned that there were some expensive boxes in the fwd cabin area, and I did not want to give them any extra reasons to quit working.

I wonder of *some* of your starting load is going thru the fuel sensor wires? Do you use electrical grease at the big wire/high amp connections? I got a small tube of the stuff from my brother who works at the local power company, and I use it on the high amp connections inside the fuse. I would expect the Big Box stores carry the stuff too?

Carry on!
Mark

[lr172]

It is apparent that you have some Ground issues. Nothing wrong with using the frame as a ground. The fact that you cleaned the terminals on the battery and got better starting performance would indicate that you have some corrosion between terminals. The very first thing I would be looking at is the ground strap between the frame or battery and the engine. If this has high resistance, it can cause the power to follow other paths and potentially do damage along the way to sensitive electronics.

You can place an ohm meter between the starter frame and the negative battery terminal. The reading will tell us if you have issues. You should also place the ohm meter between the negative battery terminal and the aircraft frame. That will tell us the health of your main ground connection.

You do have a ground strap from the Frame or the Battery terminal to the engine, correct?

Larry

[Mich48041]

Float type fuel level senders need to be grounded. The fuel tank does not provide a reliable connection to ground. The fuel level sending unit should have dedicated ground wire from the sender to aircraft ground.
Any type of grease on electrical connections will help to prevent corrosion by keeping air (oxygen) out. It does not matter if the grease is electrically conductive or not because pressure between the terminals will force the grease out. If it doesn't, then the connection is not tight enough. I have used grease on battery terminals, light bulb sockets, fast-on connectors, and etc, all without a problem.
Joe Gores

[Steve Barnes]

I will check resistance and make sure that my fuel senders are grounded and of course grease the connections too. I used heavy welding cables 0g or 1g and they were spec'd for the loads and distance and the engine is double grounded.

Steve