There is no relationship between the actual temperature of the
engine and the operation of an electric choke. The choke operates as a
function of the time that current has been passing through the
internal element. This means that you want to connect the lead to a
wire that is energized only when the car is running. In a rough sense,
this means a wire that is connected to the IGN terminal of the
ignition switch. Note that this isn't completely correct; if your car
is stalled, the choke will continue to open because the IGN terminal
is still energized even when the car is not actually running. As a
practical matter, however, I think it's a moot point.
You should also note that an electric choke is nominally calibrated
to be used with a 12V system. This would imply that you shouldn't tap
your coil wire, as it's only ~9V when the car is running. That would
be unfortunate, as it allows a neat, out-of-the-way tap. However,
there are two possible exceptions to this:
- If you have bypassed the resistance wire to your coil (e.g.
after installing a Pertronix setup) so that you always have 12 V at
- If the choke has enough adjustment in it to compensate for the
slower operation at 9V.
In addition to tapping the coil wire, there are several other
options for providing power to the choke:
- You can tap the yellow wire to the transmission shift switch.
- You can also tap the blue (stator) wire from the alternator
harness. This wire is energized only when the car is running. Given
the routing of the alternator harness and the size of the Riviera
air cleaner, you can make this tap very neatly as well. I don't
believe that this will have any detrimental effect on the operation
of your voltage regulator. The stator wire doesn't do anything
except energize the field relay in the regulator. These relays
typically don't require much current, so I'm guessing that you
*should* be able to safely tap the stator wire. If I'm wrong, it
will obvious, as the field relay won't close, which means the
alternator light will stay on while the engine's running.
- You can run a wire from terminal 4 (brown wire) of the
regulator. Although this is the most direct connection to the IGN
terminal, you'll have to route the wire clear around the engine
compartment. Cosmetically, it's the least desirable option.
If you want to dispense with all of this confusion about which wire
to tap, try this*:
- Buy a combination oil pressure sensor/switch from your local GM
dealer (part # 25036378; about $15).
- Buy a 1/4" FPT-18 MPT adapter so that it will install in the
engine block (about $2 from your local jobber).
- Replace the original oil pressure sensor switch with the new
- Connect the original oil pressure lead to the silver terminal on
the new switch.
- Tap the power lead to the blower relay (red wire that runs from
the power junction on the inner fender) and run the lead to one of
the gold terminals on the switch.
- Run a lead from the other gold lead on the switch to the choke
- If you want to fuse this circuit (always a good idea), the
electric choke that I used has a resistance of 12 ohms. A
quick application of Ohm's law gives a nominal operating current of
1 amp; a 2-amp fuse should do nicely.
As far as the taps go, I recommend Radio Shack
part # 64-3052 (Tap-In Squeeze Connectors for 18-14-gauge wire).
And because the question was asked, you can get an electric choke
for an AFB for $26.95 from Carbs Unlimited (http://www.quadrajet.com/Carter4.htm)
or about $16 from Allstate Carburetor and Fuel Injection (http://www.allcarbs.com).
* A special thanks to Bob Embrey for doing the legwork on the
proper GM switch for this mod.