Car has ac. when I start the car or activate the ignition it pops out to its setting and rests against the throttle arm .......so I know its working. with or with out the ac on it goes to the same position and raises the idle. I had it set up for the holley carb that was on the car when I got it so I cant remember how many rpm's I had it set to raise the idle. But it worked cause when I turned the ac on the idle would raise up a couple hundred rpm . Now on my new rebuilt Q-jet the selonoid doesnt raise the idle when I turn the ac on it just stays the same. and I didnt adjust it when I mounted it to the new carb so I'ts giving me a high idle with or without the ac on. the selonoid doesnt push out further to raise the idle up when I turn the ac on like before.

I know I need to adjust it for the new carb so thats why I have the wire disconected. But........ does the selonoid raise the idle by moving out further when I turn the ac on and then retract when turned off?? or does this selonoid only work at one set position ...what I set it to raise the idle at ????

I would think ..from how it worked with the other carb that the seloniod would travel out to raise the idle when I turn the ac on and then retract to lower the idle with it off....

Am I correct on this ......or am I wrong ??
can someone explain how this works because I would like to connect the wire and have it work as designed





Hammadown

 

I'm pretty sure it should move out when the AC is turned on to compensate for the power the AC draws from the engine (So it should keep the idle RPM's the same, AC or not). You adjust it by screwing the hex shaped plunger (the contact point) in or out with a wrench.

God bless, Sensei

 

Im not familiar with a 72 but on some cars the idle was set with the solenoid engaged (constant power regardless of AC position) to prevent dieseling. When the key is turned off, power is lost and the idle drops down. On my 71, I bought a used solenoid and connected to the dark green wire leading to the compressor for power. This way when the AC was on, the idle kicked up.

 

Yours appears to have a tan wire.Its an anti-dieseling solenoid not an AC kick up.Adjust your idle as Sensei said.With the tan wire disconnected adjust the screw on the side of the carb to a very low idle almost stalling.If the solenoid fails this makes the engine manageable.

 

I could swear that my idle would raise when I turned the ac on.
I remember adjusting the selonoid when I first got the car. It wasnt even engaging the throttle arm, so a buddy and I set it up. at idle with the ac off we turned the nut to bring it just shy of touching the arm and then turned the ac on and turned the nut out to raise the idle about 400 rpm more then I tried the car in drive with my foot on the brake and the idle was fine. then I shut the ac off and the idle would go back down. Thats what I remember and that was on a poorly running holley that need a rebuild ....but we made due with the carb the way it was. I do remember that before the selinoid was adjusted properly the motor would stumble with the load of the ac causing the idle to fall too low and needing the brakes to come to a stop. But with the selinoid set for the higher rpm's,the motor would not lug down and the rpm's would be up. Before with out the help of the selinoid ...I would need to ride the brake and gas coming to a stop.
Like I said before ...........the selinoid is not set for the new q-jet. Maybe I have it set too far out in its travel because of the poorly running holley it was mounted to before. maybe its so far out that its past its usable travel to raise the rpm's up more to compensate for the ac load ....I'm talking like 3 or 400 rpm's.

Hammadown

 

I was looking at a wiring diagram for a non AC car.The carb solenoid gets its feed from the TCS solenoid.I guess its possible with AC they could have used the carb solenoid for the AC kickup but if I was guessing I would say they used the TCS solenoid to advance the timing which would have raised the idle.Do you still have your TCS solenoid hooked up?If you do when at idle you shift into 4th the idle should go up.

 

DW is right. That is an anti-dieseling switch. When the power is turned off, it drops and so does the rpm, to make sure your engine stops and not rattle on.

DJ

 

I thought anti diesel selonoid had vacume to it ? the tcs selonoid shown in my 68-82 resto guide by Richard Prince shows the selonoid getting vacume and no power wire .

Hammadown

 

Actually, I think the '71 & '72 with A/C used a different system to prevent dieseling. There was a 3-second delay module on the firewall which turned power ON to the A/C compressor clutch once the ignition was shut OFF. In essence, it added the compressor's resistance to the engine which slowed the engine to shut-off. The solenoid on the carb is the TCS solenoid which worked in conjunction with the transmission and was activated in high range (auto or manual). I'm not exactly sure what it did, but I think it shut down the throttle plates for "coast-down" in high range. There is a switch on the tranny that makes connection when the box is in its highest range; there is also a temp switch (near #6 cylinder) so that it wouldn't operate unless engine had reached normal operating temp.

 

when I got the car it had a holley carb and the th400, now it has a stock q-jet, 200r4 and a weider aluminium intake. I do remember not using this on my rebuild




This was mounted to the pass side of the stock manifold. Is this part of my tcs system and why It's not working as I remember it before the rebuild . or is this somthing that connected to the stock distributer.......that I dont have

Hammadown

 

Thats the TCS solenoid

 

Is that part of my problem?......not being hooked up? was this hooked up to the th400 ?

Hammadown

 

I forgot about this but 7T1vette is correct. You don't need any of the TCS hooked. Most people disconnect this anyway. If you don't have dieseling problems and only care about a higher idle when the AC is on connect one wire of the solenoid to ground and the other to the dark green wire to the compressor. Set your idle with the idle screw with the ac off and then with the ac on set the bolt on the solenoid to the desired idle.

 

before the rebuild .............. the selonoid was set to raise the rpm's when the ac was on . and that was with only one wire to the selinoid for power.

Hammadown

 

The way I understand it before the rebuild you had 2 solenoids on your engine.The one mounted on the drivers side of the carb and the one mounted on the passenger side of the carb.The one on the drivers side(electric only) is usually energized when the key is turned on and is used to set the engine idle(it actually pushes the carb open and allows it to close).The one on the passenger side (tcs-vacuum and electric)is connected to the distributor vacuum advance line-its ability to raise engine RPM is by applying vacuum to the distributor usually when the trans goes into a high gear.(On a 4sp both 3rd and 4th-on an auto I'm not sure)
Not sure which one in your case WAS raising the engine RPMs.If it was stock I doubt it was the one on the drivers side.
Talking about what was is behind you.Now that you have done some mods what do you want to do?
Take your test light and test the tan wire with #1-key off...#2-key on...and #3-engine running and AC on.Let us know what you come up with.