Where do you hook up an engine idle solenoid?

[nge]

Hi All,
I have a 73 Charger with a 440 and aftermarket air conditioning
I have been staring at my 73 service manual for hours and I get 3 different schematics.
Page 8-148, figure 16-65 shows the idle solenoid wire going to a
3-way splice to bulkhead connector 23, the ignition ballast and the alternator regulator.
Page 8-148, figure 17-65 shows the idle solenoid wire going to a 3-way splice that goes to the electronic ignition control, alternator regulator and the ignition ballast.
Page 8-129 shows the idle solenoid wire going to the middle field (F) connection on the alternator.
and Page 8-128 shows the idle solenoid wire going to the middle field (F) connection on the alternator.
Perhaps this is all the same way, just executed differently.
Can anyone show me a picture of their set up?
are they all in effect the same connection?
Any help or better suggestions would be appreciated
thanks
Vic

[b5blue]

If using Sanden type compressor it's not needed. Modern compressors demand much less drag than old ones. I just installed on my 70 Charger and was worried about the same thing but not an issue. If it was needed you could tap the compressor clutch wire to turn on a relay fed from Alt. output.

[nge]

Thanks Neal,
Yeah I will need the solenoid, because of my cam selection, my car stalls when I turn the  a/c on.
I have read elsewhere about tapping into the compressor clutch wire, but the common complaint was that every the compressor cycles off and back on (in traffic) you have to blip the throttle to get the solenoid to hold.
But, if that's the way things were on in the old days, that's OK by me.
thanks
Vic

[John_Kunkel]

You don't really have a choice; tapping into the ignition circuit is the same a turning the idle screw on the carb...kicks up the idle whenever the engine is running.

Tapping into the clutch circuit kicks up the idle only when the compressor is running, this is the common way to wire an idle solenoid. To prevent the constant clutch cycling, adjust the A/C control to a colder setting.

[Nacho-RT74]

That source ( all those are the same one ) is used for save from dieseling/run on, being that screw the one for iddle adjustment and despiting the driver side one.

If you want to use for A/C need to hook it up to compressor clutch source.

[b5blue]

  What is happening is a voltage drop that causes the solenoid to dropout. RPM's drop so A/C clutch voltage drops off cutting out the clutch also. Weak Alt output @ idle most likely is doing this. By turning on a relay that turns on the solenoid you only tap a tiny fraction of the power that feeds the clutch. (Remember the solenoid is fighting against the carb return spring.)
 As the A/C blower fan is taking 15 amps or so off Alt. idle output on top of ignition and any other running loads your just out of amps at idle. (Most likely.) Get me?

[nge]

yes! I get it, thanks!
I got a solenoid and I already have a relay, so here we go!

[b5blue]

Hook things up and test to solenoid holding against spring pressure first. If it holds without the load from A/C system at idle then you know if it drops out WITH A/C your Alt idle output is too low.

[John_Kunkel]

It's not a system voltage drop that causes the solenoid to drop out, it's the compressor clutch power shutting off due to the temperature in the evaporator...perfectly normal and the timing of the clutch off/on cycle is dependent on the temperature selected (warmer setting/lower fan speed causes more frequent cycling).

Most idle solenoids don't have the power to actually push the throttle lever open against the return spring, they're merely a stop, so every time the clutch disengages the solenoid has to be reset by blipping the throttle. The alternative is to find a solenoid with power or choose a colder temperature on the A/C control.