Electrical Help- Why is my switch not working?
 

I'm at my wits end here.

I have a SPST switch with an LED light rated at 20A. It has three contacts on it.

For the + contact, I have it wired to a 12v power. Everytime I test that wire, it shows 12v, so I don't believe I have any issues with this wire/connection. (It's tapped from the fuse box using one of those add-a-circuits)

The accessory contact connects directly to a 1/2 inch Barbed Hose GRAVITY-FEED 12V DC VDC Plastic Nylon Solenoid Valve.

The ground contact goes from the switch to the same threaded bolt the ECU mounts to under the floor mat of my XJS, then continues to the 1/2 inch Barbed Hose GRAVITY-FEED 12V DC VDC Plastic Nylon Solenoid Valve.

The valve has two contacts, basically one comes from ground, shared by the switch, and the other contact is connected directly to the switch.

I cannot get this switch to light up consistently. It comes on and then shuts off after a few seconds. I cannot for the life of me figure out why. Should I not be sharing the ground between the switch and the valve? I basically took the two wires, spliced them on to the same eyelet and bolted them down to the same ground post the ECU uses! Is that wrong?

The switch works. I've tested this whole assembly using a battery. It worked great! Once I put it in the car, it doesn't seem to want to work.

I'm using 14awg stranded wire.

Again, the 12v wire always tests with power, so its not that one. I've tested continuity on the other wires, successfully. Well, almost. Something wasn't testing up on the ACC wire, but once I cut off the connector and re-terminated the wire, it tested good. I'm about to test it again....but I do get the LED to light up, it just seems to want to do it when it wants to.

MMMMMMMM.

Earth be earth, and I cannot imagine why splicing them would do that, but Electrickery is "female" by nature.

I would split the earths, and use the ECU mount for the LED earth, and a separate location for the Solenoid, should take less than 10 minutes and ONE beer to do that.

Thanks for the response. I'm going to try to replace the switch first, as I agree, earth is earth....

Will keep you posted.