Sensor above oil filter 3 wire

[Finkaire]

Sorry if it’s been discussed, what is the 3 wire switch above the oil filter.
Trying to eliminate as many oil leaks as possible. Changed the valve cover gaskets, and the oil pressure switch behind the distributor. The 3 wire switch is leaking, exactly what is that sensor?

 

[Rusty Nail]

Ask @Redfish

 

[PrairieDrifter]

It should be for the dummy light and depending on year will control the choke or fuel pump on startup.

 

[Redfish]

Ask @Redfish

Sorry, this one I don't know the answer to. I can speak with some authority about a 1987 because mine is relatively low mileage and is all original.

1987 had a single wire sending unit right above the oil filter and a two wire switch below the distributor.

I am sure you and several other folks on this forum know more about the other years than I ever will.

 

[Rusty Nail]

Aw come on dude, that was pretty funny. At least you're a good sport. i'm certainly no authority -I just like talkin ish on the internet.

 

[Ricko1966]

Sorry if it’s been discussed, what is the 3 wire switch above the oil filter.
Trying to eliminate as many oil leaks as possible. Changed the valve cover gaskets, and the oil pressure switch behind the distributor. The 3 wire switch is leaking, exactly what is that sensor?

What year and model is your truck?

 

[Finkaire]

1984 C10, 305ci California car

 

[bucket]

Yeah, it has to do with the choke operation and the choke light on the dash.

 

[Turbo4whl]

So there were several ways that GM wired the choke, some use a relay. Your '84 most likely without the relay.

Pull the plug off you may only find 2 spade pins, not 3. The two blue wires, (hard to see) are jumped together in the plug.

 

[Rusty Nail]

Didn't that same circuit have something to do with the low oil pressure warning that turns the brake light on?

Sometimes itll turn on while crankling?. No?

What am I thinkin of?

 

[SquareRoot]

Knock knock. Who's there? Oh wait that sensor came waaay later than 84. Unplug it and find out.

 

[BRetty]

I think:

It's a general oill pressure sensor/switch, that was connected to the TH350C torque converter lockup circuit. Were/are the wires going to it green and yellow?

 

[Ricko1966]

^ I am 99.99 percent sure it is the oil pressure sender for the choke heater. It is so the choke only gets power when the engine is running. Not just anytime the key is in the run position. FWIW the only external components to the th 350c are the tvs,the vacuum switch,and the brake switch.which control converter lockup. Everything else should be the same as most other th350 s

 

[Turbo4whl]

@Loren So did you pull the plug off and only find 2 terminals on the switch?

Here is how the heated choke and choke light work:

Key on, current to the choke light and current to the switch on the light color wire. The switch is open with no oil pressure. The current from the choke light bulb goes to the pressure switch. This is the 2 common wires on the switch plug (blue wires). From there the bulb current goes to the choke and grounds through the heater element.

The .03 amp the bulb needs, is not enough to heat and move the choke. The choke light says on.

Start the engine, oil pressure has closed the switch. Now the current that was applied to switch goes to both blue wires. One wire up to the choke with no bulb resistance, and heats the choke. Now with positive current on both sides of the dash choke light and no ground, it turns off.

 

[Turbo4whl]

Found it:

You must be registered for see images attach