Sensor above oil filter 3 wire

[bucket]

@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.

What is still a mystery to me is when I Holley swapped my '84. I used the original choke heater wire on the Holley carb, but the choke light on the dash stayed on. I don't recall if the choke operated or not, but I'm kinda wanting to say that it didn't. I ran a dedicated IGN wire to power the choke and solve the issue.

Maybe the Holley choke coil doesn't draw as many amps? I dunno, it still doesn't make much sense to me.

 

[SirRobyn0]

^ 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

Yes this is my understanding.

What is still a mystery to me is when I Holley swapped my '84. I used the original choke heater wire on the Holley carb, but the choke light on the dash stayed on. I don't recall if the choke operated or not, but I'm kinda wanting to say that it didn't. I ran a dedicated IGN wire to power the choke and solve the issue.

Maybe the Holley choke coil doesn't draw as many amps? I dunno, it still doesn't make much sense to me.

On that system did you get a full 12 volts? When I got my truck it had an Edlebrock on it installed by the PO. Took forever for the choke to come off. I can't recall for sure but it was feeding less than 12 volts up the wire. Maybe 6 or 8 volts? So I ran an IGN hot wire to it to solve it rather than trouble shoot the circuit. I really have no idea if that circuit is suppose to be like that, but if it is that might be why that circuit does not like aftermarket carbs.

 

[bucket]

Yes this is my understanding.

On that system did you get a full 12 volts? When I got my truck it had an Edlebrock on it installed by the PO. Took forever for the choke to come off. I can't recall for sure but it was feeding less than 12 volts up the wire. Maybe 6 or 8 volts? So I ran an IGN hot wire to it to solve it rather than trouble shoot the circuit. I really have no idea if that circuit is suppose to be like that, but if it is that might be why that circuit does not like aftermarket carbs.

I really can't remember. It was like 12 or 13 years ago and I was just trying to make the truck run again.

 

[Turbo4whl]

What is still a mystery to me is when I Holley swapped my '84. I used the original choke heater wire on the Holley carb, but the choke light on the dash stayed on. I don't recall if the choke operated or not, but I'm kinda wanting to say that it didn't. I ran a dedicated IGN wire to power the choke and solve the issue.

Maybe the Holley choke coil doesn't draw as many amps? I dunno, it still doesn't make much sense to me.

I used the original choke wire on my '82 with the Holley and it worked fine. My guess, your pressure switch was bad or had a very poor connection.

 

[SirRobyn0]

I really can't remember. It was like 12 or 13 years ago and I was just trying to make the truck run again.

I know the feeling....

 

[Finkaire]

Great Turbo!
still haven’t been able to find the part or even a picture.
definitely looks to be what I’m looking for.
Thanks

 

[MikeB]

That's a drawback to electric chokes. They are totally unaware of intake manifold temperature, and continue to open as long as ignition voltage and oil pressure are present. Problem is it could be a cold winter morning, and while you're cranking over the engine, there's enough oil pressure to close the switch. So, the choke is fat, dumb, and happy to start opening.

I have no idea why GM got away from "divorced" bi-metal chokes that actually responded to intake manifold temperature. What a concept!

 

[Finkaire]

It’s a 2 wire pressure switch, 3wire plug fooled me