Oil pressure warning light - start up

[4corsa]

Forgot one

[4corsa]

Well, the socket is getting power, test light illuminated with key turned on, and went off when key went off. Has to be something messed up in the socket base. Bulb does seem loose when inserted.

[4corsa]

Turns out the blue ground wire is not grounding. When I touch the bulb contact wires to the red wire and my grounded test light probe, the bulb illuminates.
Now what?!

[4corsa]

...as seen here:

[po18guy]

The tiny T5 sockets have rather fragile connectors in them. Have a look at a known good socket and chances are that the oil light socket contacts are dirty or bent out of shape. Carefully reshape them using a dental pick if you have one and do a live test. Some of the pressure exerted by the contacts on the bulb is caused by the rubber socket being squeezed into the gauge receptacle. With the key on, sometimes you can squeeze the socket and the bulb will light. As I found out, LEDs are polarized and if they don't light up, flipping them side-for-side or end-for-end will solve the problem.

EDIT: Oh, joy! No ground. Now to consult the plate of spaghetti wiring diagram? Is the blue a common ground? 

[4corsa]

I don't believe it's a common ground.(but not sure). It's isolated going to and from the first connector block. Anyone happen to know where this circuit is grounded to the frame? Now thinking this could be related to my intermittent starter issue. Need to find the ground point and clean it up.

[docc]

No frame ground from the factory. The light grounds through the switch to the engine.

What about cleaning and treating the connectors with Caig DeOxit and resecuring them?

[4corsa]

Thanks Docc, I'm on it.

[4corsa]

Ok terminals cleaned, scuffed, sprayed and re-connected no difference for the warning light. Bulb won't light when touched to the two bare terminals in every which way, but it lights when touched to the red wire and grounded test light with ignition switched to on.

[4corsa]

Also, as a verification, I clipped my test light to the blue wire and touched the probe to the red wire with ignition on and did not light. Definitely not getting ground.
I'm thinking may have to cut the blue wire and connect the blue wire terminal directly to the frame, unless someone has a better idea.

[gstallons]

First things first . With KOEO and the oil pressure switch unplugged , the wire should have battery voltage . You have a good circuit  . 12v . If it does go to the next step .

When you ground the wire at the oil pressure switch with the KOEO the light should be on . Y or N ?

[4corsa]

I have not checked this, and first need to locate the oil pressure switch.

[4corsa]

First things first . With KOEO and the oil pressure switch unplugged , the wire should have battery voltage . You have a good circuit  . 12v . If it does go to the next step .
When you ground the wire at the oil pressure switch with the KOEO the light should be on . Y or N ?

When you say "...the wire should have battery voltage", which wire? The wire to the oil pressure switch, or the hot wire to the bulb?

[4corsa]

Ok so with koeo, using my grounded test light with probe inside the oil pressure switch socket, I am getting NO light, no power.

[4corsa]

Also, I'm assuming the connector to the oil pressure switch is supposed to have just one wire.