[yzinger]

Guys, can anyone explain why i have 12volts with ignition on to my wire that connects to the electric choke on my q-jet...but, if i attach said wire to choke (again with ignition on) i have almost no voltage (.5) - I can not figure this out.

Thanks
B

[2002Z4CSS]

Originally Posted by yzinger

Guys, can anyone explain why i have 12volts with ignition on to my wire that connects to the electric choke on my q-jet...but, if i attach said wire to choke (again with ignition on) i have almost no voltage (.5) - I can not figure this out.

Thanks
B

The choke coil acts like a resistor and drops the voltage.

[Schurkey]

I'd have said your source voltage is being drawn through a ballast resistor. With no load, you have full voltage. As soon as the wire is connected, the current flow through the resistor drops the voltage.

WHERE is the source wire coming from? A switched fuse or terminal in the fusebox? From the wire powering the coil? Somewhere else?

Are you measuring the voltage on the + or the - side of the choke stat?

[pfilean]

I think Schurkey is on the right track.

[george kujanski]

I'd say your source wire is not connected directly to a 12 volt source, rather thru some fairly high resistance.

Try a jumper from the battery directly to the choke coil, you should get battery voltage on the terminal of the choke, and the choke should start to warm up.

If so, you need to find the source of your choke wire and insure it's from a direct connection to switched battery voltage.

George

[Blued and Painted]

What year and model?

[yzinger]

1980 Trans Am - was 301 turbo, now 406 pontiac.

Had existing choke wire coming out of bulkhead. As i said, full 12 volts when not attached to coil.

I test the wire with a meter before attaching by one lead to ground, other to wire. Once attached i put on lead to ground and one to the terminal on choke.

Maybe it is only supposed to draw .5 but seems strange to me.

[lust4speed]

It sounds like that instead of a fuze blowing if you grounded out the wire, that you might see a warning light on the dash light up - or if you have gauges, one of them peg out.

[Blued and Painted]

It will read 12v with no load. Sounds like a wire just about to brake into. maybe only 1 or 2 strands still connected. the choke heater is not a big load. Maybe 2 amps.
Find a diagram and check back to the source.

[John O.]

I will be switching carbs on my 71 gto and running an electric choke. I know it has to be switched power just wondering what would be the best way or place to run it from.

[jmt455]

Do you see that full 12V with the engine actually running or just with the ignition key in the "run" position?

[BVR421]

JOHN O,
Ive never done it as Ive never needed to wire a electric choke from scratch but lots of people claim good results tapping into the wire that powers the window wipers. Its only hot when the motor is on and its a convenient simple place to get that power.

[Blued and Painted]

The easiest source is the off the wiper motor. It's already fused and close to the choke housing.

[jmt455]

Originally Posted by yzinger

1980 Trans Am - was 301 turbo, now 406 pontiac.

Had existing choke wire coming out of bulkhead. As i said, full 12 volts when not attached to coil.

I test the wire with a meter before attaching by one lead to ground, other to wire. Once attached i put on lead to ground and one to the terminal on choke.

Maybe it is only supposed to draw .5 but seems strange to me.

It's not drawing 0.5V; you're reading a 0.5V differential to ground after connecting the choke coil. If you want to see what current the choke heater draws, you need to connect the ammeter in series with the coil heater.

I think your reading just indicates that the choke heater coil is getting 12V; the 0.5V reading indicates there is more resistance in the coil circuit than there is in your meter.

Sounds right to me, but I'm no electrician.

[yzinger]

we might be onto something as the choke light in the dash comes on and does not seem to turn off until i unplug the wire.

But, with the meter showing me 12 volts to the connection doesnt this mean i do not have a short?

Also, i see the 12volts with key in on position as well as when car is actually running.

Question - to test is the spring will actually expand and contract could i hook the wire to the thermo (not installed into choke housing) and see it move? - i guess i would have to ground it out.

[Willshire]

You could measure the resistance of the coil between the hot and ground wire to see how much resistance is in the coil of choke. With this reading you should be able to get your current draw from ohm's law formula. A=V/R. Perhaps your resistance is out of spec and the choke is no good. If you take the choke out and apply a 12V source and ground to it, does the spring rotate?

[yzinger]

I will do that tonight..This is a new carb from SMI and the thermo and spring look brand new. I will apply the 12 with a ground tonight and ensure the spring moves. Then i will try to figure out how to re-install the thermo. You see, the boxed end of the spring must go over one of the fingers inside the choke housing. All the pics i can find online only show one finger which would make it easy . Mine has two.

Originally Posted by Willshire

You could measure the resistance of the coil between the hot and ground wire to see how much resistance is in the coil of choke. With this reading you should be able to get your current draw from ohm's law formula. A=V/R. Perhaps your resistance is out of spec and the choke is no good. If you take the choke out and apply a 12V source and ground to it, does the spring rotate?

[Blued and Painted]

make sure the heater gasket is removed for a good ground.

[yzinger]

agreed...luckily mine has no such gasket.

Originally Posted by Blued and Painted

make sure the heater gasket is removed for a good ground.

[jmt455]

Originally Posted by yzinger

we might be onto something as the choke light in the dash comes on and does not seem to turn off until i unplug the wire.

IIRC, the choke light should go off when the engine starts

But, with the meter showing me 12 volts to the connection doesnt this mean i do not have a short?

If you have 12V at the coil power feed wire, you don't have a short in that feed circuit.

Also, i see the 12volts with key in on position as well as when car is actually running.

You should have 12V at that point when the car is running, but I'm surprised you see 12V there when the key is on but the engine is not running. Most of the choke heater circuits from that era are energized through the oil pressure switch contact. That means you wouldn't see 12V at the choke heater until the oil pressure is above the minimum level that turns off the "oil" warning light (usually about 10psi).

Unfortunately, I don't have a wiring diagram for the 1980 301T so I'm not certain how your car's circuit is designed.

Do you have the proper (specific model & year) wiring diagram for the car? That will make it much easier to troubleshoot.

Question - to test is the spring will actually expand and contract could i hook the wire to the thermo (not installed into choke housing) and see it move? - i guess i would have to ground it out.

Yes, you can test it that way, as long as you ground the thermo unit exactly as it is grounded when installed in the housing.