Electric choke wiring with a relay?

[drdano]

I'm getting ready to wire in my electric choke with a relay and need some advice on what to trip the relay with.  The car is a '62 Galaxie with a generator.  I have a one-wire idiot light for the oil pressure, but two mechanical gauges to keep an eye on things. 

Plan to use a fused line from the battery to the relay on the power source side.  Would a small line to the armature output on the generator cause a problem for the switch input to the relay?  That way the relay only powers up the electric choke when the motor is running. 

What amp fuse should I run on the power input to the relay off the battery?

Thanks all.

[drdano]

An update on this, and I'll sort of answer my own question here...  I already got burned my first day of the new motor running in traffic forgetting to flip my toggle switch for the electric choke causing the motor to run super rich and angry, so this motivated me to get the relay wired in place.  What I ended up doing was hooking the switch lead from the relay to the Armature post on the generator, which does turn 14v at idle, but no volts when ignition is on and motor is not turning.  I don't have any traffic time yet, but this should work a-ok.  I'll update again when I have more road time.

[jayb]

Thanks for the update; I've never run an electric choke, so I had no clue how to handle that situation.  Sounds like you've got it covered...

[My427stang]

Should work great assuming it is stable voltage. 

I have also had success using a hot wire that is hot when in run, but not in accessory.

Although yours is technically the way it should be, only heating up when the motor is running, very rarely would any of us sit with the car in the run position without the engine running.

[drdano]

Update.  I spent the afternoon yesterday doing AFR tuning on the car and fixing little problems that are popping up with the new motor.  Fuel gauge sender decided to die, thats a new one on me...

Anyway, the relay worked flawlessly all day through multiple jet changes and road time.  The motor is idling at 950rpm with the big (you guys call it small) hyd roller cam which is keeping the generator ...generating.. 14v idle which is plenty to supply the switch voltage to the relay.  One mishap was I had a 9amp fuse in the lead from the + battery side of the starter solenoid which popped mysteriously on the first start with the relay hooked up.  I stuck a 20amp fuse in there and it survived the rest of the day.  So far I'm happy with the relay setup.