Revisiting the discussion about powering an electric choke. I've pretty much settled on using the three prong oil pressure switch that allows a lead from the alternator to be connected to the oil pressure switch, then to the electric choke. Looking at my wiring I wanted to see if another option is possible.
This engine was converted to an HEI distributor. There is a black/yellow wire coming from the firewall connector that was connected to the exterior coil when the breaker ignition was in use. Converting to HEI seems to make that part of the circuit redundant. Could that feed be used to power an electric choke?

 

Pretty common to run off the wiper feed, mine was set up that way bofore I got it. Joe's wiring in the sticky looks better if I ever get around to it but works fine as-is.

 

No.

The reason why that wire was disconnected is that it is a resistor wire. providing less current than a regular wire. If you use it, the choke will not heat properly, and will remain engaged for too long.

- Eric

 

If you are using the PS64 switch, then simply run a fused lead from the alternator threaded BATT terminal to one lead of the switch. The switch is open until there is oil pressure. I'm using this arrangement on my 62 with no problems in over two years now.

 

an alternative method is to use a relay with the existing oil pressure switch. break into the wire between the switch and the bulb(under the dash), connect one side of the relay coil to this point. the other side of the relay coil gets connected to the fused side of the gauges fuse. connect the wiper arm(the piece that moves) of the relay to the heater circuit(on the fused side or run your own fuse from the unfused side). the heater circuit is only energized when the ignition switch is in the on position-not live in accessory). lastly, connect the n.c.(normally closed) contact to the choke wire using 16 gauge wire or larger(14 gauge). optionally, you could get some sort of audio annunciator and connect it to the n.o.(normally open) contact, then you would immediately hear about a loss of oil pressure that lights the light.

how it works:
*no oil pressure>light on>relay coil energized>choke power off>optional annunciator sounding.
*oil pressure above switch closing pressure>light off>relay coil not energized>choke power applied>optional annunciator not sounding.

proper fusing of a 16 gauge choke circuit would be at 20 amps, this will power any electric choke properly, with an adequate margin to prevent false fuse-blowing.

if you're installing hei, you can wire another relay coil from the ignition terminal(other side of the coil to ground) and use the ignition relay output to supply power to the choke relay wiper too. in this case, you could connect directly to the junction block using a 12 gauge wire with a 30 amp fuse near the junction block. recent gm vehicles have some decent relays that are high current and weather-sealed(used in the blower circuit and electric fan circuit(s)).

that's how i have ernie wired(without annunciator) for over 6 years & no problems(2 relay circuit).


bill