Inliners International Forums General Discussion Electrical Electric choke @ Oil Pressure Sw. not HEI terminal

Is there any reason why i can not run my electric choke wire from my edelbrock to my HEI terminal @ the dist ???
It would sure be easy & make for a clean job as all the other engine wiring is on that side of my 292. The oil pressure sender, hei, radiator fan sensor switch@ the thermostat housing, & wires to the starter, etc.

You can run it from anyplace that has 12 volts when the key is in the ON position and it will work. The bad news is the choke element will begin to heat as soon as there is voltage going to it whether the engine is running or not. The preferred way is to run it from an oil pressure switch that has 3 terminals on it. A normally closed side that brings the oil light on when the pressure is nothing or very low, and a normally open side that will close once the oil pressure starts to build up. The choke is wired to the normally open side so the choke element gets no power until the engine has fired and has began building oil pressure. Thousands of electric chokes are wired direct to some 12 volt source but imagine a cold day and the engine doesn't fire up right away. Now as long as the choke has voltage it is opening and an engine that began as just a hard starter has now lost the cold start help that a closed choke provides.

The 3 prong oil pressure switch was used on quite a few GM engines through the 80's and can be had at any parts store for under 10 bucks. It fits right into the oil sender tapping on your inline.

I agree with Mike G, as a side note the electric choke is essentially a heater that heats up bi-metal strips to open the choke plate. Electric heaters are just a little resistance away from being a short. Despite it's small size the electric choke probably draws a 1/4 to a 1/2 amp of current, as to whether it would drop the voltage at the HEI I'm not sure.

Larry

just to be clear about this wiring::
run the black ground wire of the choke assy to the pressure switch (normally open post) and the red to a fused power source, 5-10 amps.

thanks for that bit of valuable knowledge gents
now that i ponder that it makes sense.

update 5/23/06 the edelbrock web site instruction says:
''do not wire to coil or alternator''

ya just have to love this forum

Dear Caroline;

I think their right.

For the HEI to make the (higher) HV it would need a larger/heaver primary winding for the coil. I believe this uses a #10 wire to do this.

Besides; Why heat the choke up (waisting power) if you don't have to??

I wasn't aware of the 3 wire oil switch but it makes cents. The more the alternator works the more gas used.

Good luck.

NO. The black wire is a ground. Nail it to the engine block or intake manifold. The hot wiring sequence is as follows: You should have installed the 3 pronged oil light sending switch into the side of the engine. One terminal will be the common, or hot from the ignition switch, when the key is on. Another will go to the OIL idiot light and with the key on and engine not running the oil light will be lit. From the remaining terminal on the sender switch run a 16 gauge wire directly to the hot terminal on the Edelbrock choke. There should be no power on it with the key on until you start the engine and the oil pressure builds up to close it thus energising the choke heater coil. If this does not energise when the engine starts then you have to swap the 2 wires for the oil light and hot from the key that were already there with each other because you are feeding the wrong side of the normally closed part of the switch and not the common side.

It is easier than it sounds.

And do as the Edelbrock directions say. Don't run it off the HEI or the alternator.

I thank you mike

I went to 'flaps' and found many an oil pressure switch. some w/ one, two and three terminals, different threads and activations pressures. I choose a (carquest # PS-133) 1/8'' npt, pipe thread, dryseal, switch which states term A to gnd. term B opens @ 3-9 psi N/C, term C closes @ 11 psi N/O. ''Also used simultanouesly as an electric choke heater switch''. used on AMC, Chrysler, GM, Ford, Chevrolet and others.
It's now pretty clear.

You're welcome Caroline & Jim. As far as running the wire to look neat you can run it right alongside the power wire for the HEI and contimue along the small steel vacuum line that runs in front of the valve cover, or run it behind the head in some of that plastic wiring covering and with a couple of small one hole nylon supports on the valve cover screws run it along the left rear half of the valve cover and then to the choke housing. Just be careful of it drooping onto the exhaust manifold flanges if you do it this way.

Enjoy the ride,

Mike, you need to rethink your wiring for the 3 prong sender. It will work fine for the choke heater, but the oil idiot light won't work. The oil light needs a ground when the oil pressure is low or not there. The original sender provided this ground. With the sender wired "hot from the ignition switch", you will have two conditions. 14 V on both sides of the oil idiot light with the switch closed. 14 V on one side of the light when the switch is open and no ground.
Either way, no light.
If you run the common connector on the sender to ground, 14 V to the choke heater and the choke heater ground wire to the sender, both circuits will be complete to ground and isolated.

Richard. The ground for the oil light is provided by the bulb socket. The switch I speak of has all 3 of it's terminals electrically insulated from the switch body. The circuit runs power out to the switch and then back through the bulb filament to ground at the bulb socket. The vehicle involved in the question has the bulb sockets grounded as it is a custom wiring installation. Nothing to rethink.

A single terminal oil light switch in fact does provide the necessary ground to the bulb as you state. That's not what we are talking about.