From a trouble shooting Book.....
Simply using a switched power source, especially one that is hot in the ACC position, can cause the choke to open prematurely if the key is on but the engine is not running.
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 the coil.
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 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 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.
