Switch failure

[Brambo]

Yesterday morning as I entered the garage to start work on my airplane, I noticed that everything on the main buss was turned on. I naturally assumed I'd forgotten to turn off the master battery switch. Imagine my surprise when I went to turn it off and found it was already off. I have a Cessna type switch (from Spruce) with a split Alt/Bat rocker. Sure enough after some investigating I found that the Bat side was connected no matter what the position of the switch. I've only had this switch installed for about 6 months so it seems strange that it should fail so soon.

My question is, did I just get a bad switch or is it possible that something else caused the failure?

Bill Rambo
RV-7A

[Lycosaurus]

Originally Posted by Brambo

... did I just get a bad switch or is it possible that something else caused the failure?

Hi Bill,

You may have received bad switch (in any case, it looks like it is bad now).

Did you install a free-wheeling diode on the master solenoid? This diode is installed with anode on the solenoid control (master switch) and the cathode on the battery lead side of the solenoid.

The diode prevents repetitive damage to the switch from inductive energy sparking across the switch when powering off. This damage can be seen as pitted contacts, or possibly a welded contact.

If you did install the diode, then you have a defective switch (or a bad diode).

[Brambo]

yes, I did install the diode. So, hopefully just a bad switch. I'll try and take it apart later today and see if I can tell anything by looking inside.

Bill
RV-7A