rpms with a.c on isnt it suppose to go up ?

[candymancan]

Isnt there a sensor or somethibg thats suppose to make the rpms go up when the a.c clutch is on ? When i turn my a.c on it will drop 100-150rpm and it brings ny idle in gear to lile 600rpm which is too low to spin the alternator and get enough current to the vehicle.. If i step on the gas pedal to raise it 150rpms back to 750 the voltage goes back from redline to 13v.

I can manually adjust the rpms higher to compensate obviously on the carb.. but raising them to 850rpm vs 750 in gear is kinda high just to bring it to 700 with the a.c on vs 600.. specially in park when high idle kicks in when you go to park its at 1100rpm vs 950 or so prior and thats too high .

I know my 90 has that black thing with the nipple on it that sets the rpms.. but i dunno if it has any relation to the a.c clutch when the a.c comes on im certain it does.

If so where do i start looking to get this fixed so the rpms dont drop so low with the a.c on.. Im not a fan of sitting on the redline at a stop light when my headlights and a.c are on due to the a.c dropping the rpms to 550-600.. when its on

[kansasboy001]

Amc did not use a solenoid or idle kicker for the ac however you can simply adjust the idle with the screw on the carb and re wire the solenoid with the clutch wire so it will bump up the idle.

Spec is for 600 +150 -50 rpm in drive anyway so there may be a problem with your alternator if its not outputting enough around 600 rpm. I don't have ac yet but idle is 625 in gear and my alt puts a constant 14 at idle.

[candymancan]

wait till your a.c clutch kicks on lol mine is fine with it off too once the clutch kicks on and the fan is on full blast with the headlights and fog lights on and brake lights at a red light the battery gauge drops . headlights dim.. turn signals go slow. Its a brand new 90a alternator and a 850cca battery.. It isnt the alt or battery.. or grounds there all new i eveb added two grounds.

Itll run fine at 13+v with headlights off.. but with em on there isnt enough power for all of this at 600rpm or less


So youre saying to cut the wire on that black nipple thing on the thottlre lever and wire it into the a.c ? Which wire ? the one on the compressor ? There are two i believe. Im assuming the power wire and when the nipple thing gets power itll push the nipple out raising rpms ?

[kansasboy001]

Take the wire from the solenoid and wire it with whatever engages the compressor clutch. Set your initial idle with the screw on the carb body then turn on your ac and everything and adjust idle with the solenoid until it all works. That way you'll only bump up the idle when the compressor clutch is engaged. This is the way gm did it

[fulsizjeep]

I am a little confused. You say "get this fixed" as if to imply it is broke. I have been driving these things with AC since 1980 and if it idles too low, I find a happy place with the idle screw adjustment. But, that is just me.

[ghcoe]

My "77 has a solenoid that kicks the idle up when the compressor kicks in. It is simply wired into the same wire that goes to the clutch and pushes a plunger out to kick the idle up a bit.

[Stuka]

I have seen some Jeeps with the solenoid, and some without. My J10 for instance did not have one, its an '81. But I have seen some late 70's ones with it.

[kansasboy001]

you also could switch to an alternator that has a higher output at low rpms. Im assuming you have a 12si which outputs 30amps at 1600 alternator rpm which with our crank to alt pulley ratio of 2.1 is 760 engine rpm. A cs series or 15si has 40 amps at the same rpm. That 10 amps could make a big difference.

[will e]

I have the anti-diesel solenoid on my Jeep. I use it to bump up the idle speed while wheeling.

The solenoid is not strong enough to extend against the spring of the carb. It only extends when there is little to no pressure on it. Which is what it was designed to do.

If you have it hooked up to the AC compressor it will engage when the compressor is on. If the compressor turns off while you are at idle the solenoid will close. If the AC compressor turns back on the solenoid will not bump up the idle speed if you are at idle.

[candymancan]

My "77 has a solenoid that kicks the idle up when the compressor kicks in. It is simply wired into the same wire that goes to the clutch and pushes a plunger out to kick the idle up a bit.

See thank you.. i knew that solenoid is supposed to kick up the idle when the a.c clutch is on.. mine doesnt.. Maybe mine is bad. Ive read this before in the past as well

So if it isnt kicking up idle then it does need fixed. I coulda swore that was already wired into the compressor.. I shouldnt have to adjust the carb everytime i want a.c and then no a.c Thats silly.

Ima follow the wire and see where its actually leading too.. Compressor only has two wires on it they lead to that switch on the metal line with the sight glass.

[will e]

Ghcoe wrote that his performs that function. However, it was never a function from the factory for the solenoid to kick up the idle when the AC clutch is on. It is an anti-diesel solenoid.

That being said I repurposed mine to add a bit of idle speed as well, mine is connected to a manual switch.

[ghcoe]

Ghcoe wrote that his performs that function. However, it was never a function from the factory for the solenoid to kick up the idle when the AC clutch is on. It is an anti-diesel solenoid.

That being said I repurposed mine to add a bit of idle speed as well, mine is connected to a manual switch.

Weird! It all looked OEM to me when I was working on it but, going by the wiring diagram it is called a throttle closing solenoid. Works great as a idle step up motor for the A/C though. I have never had any issue with dieseling. I wonder if it was a anti-dieseling solenoid without A/C and a idle step up motor with A/C?

[kansasboy001]

It was an anti diesel solenoid regardless of ac or not. Never had anything to bump up idle for ac. 600 rpm should produce 24 amps or so with a 12si which should have been stock on a 90 unless the heavy duty alternator option was chosen then it would be the rare 15si which would output 32 amps. What is the model of the alternator you have? If it's a 10si derivative it would output less than 10a due to the design. The 10si was phased out in the early 80s but parts stores have them as an option for all years.

[candymancan]

Whatever 90 i git from autozone lol ill look at the model tomorrow.

It puts enough voltage at 600rpm with just the a.c on.. or just the headlight and fog lights on.. but all of them together it doesnt.. Works fine at 700rpm though.. but with it all off 700 goes to 800 or so.. too high imo

Ill rewire it to compressor like stated

[HowardT64]

ill have to watch this on mine...see what happens. I dont recall it ever having an issue...

[SJTD]

I always thought they bumped idle due to the additional load of the pump and to get mo flo through the condenser. The additional electrical load aint that much.

[candymancan]

the load is alot.. When i turn the fan on i can move the temp to heat and the comoressor will click off. I can watch the rpms on my tach i install jump 150.. Even hear it.. Then when i turn the temp down it clicks on and the load drops 150 and if its at 600 rpm at a red light with headlights and fogs on the power drops to red line and every dims.. turn signals blink every 2 seconds.. if i tap the gas to raise it up 100 rpms voltage goes back to 13v line everythings brightens up and turn signals blink faster.

Why is it so hard for ppl to concieve the alternator not being able to output the needed power at 600 rpms for a load that large ?

Some of you also keep ignoring when i say headlights and fog lights and brakes at a red light.. It works fine if its just headlights.. or just the a.c.blower and no lights like during the day.. but all of it together it bogs down in power. Fog lights use alot of power i noticed.. If i flip them off the gauge will jump up with everything on.. if i turn them on the gauge drops.. but if idle goes up the voltage is fine.

The 90A just cant power all this at that lower idle speed.. Ive read tons of ppl saying its normal for headlights to dim at idle with everything on.. No it isnt.. and i wont accept that lol..

specially if i have the fan on full blast lol

[kansasboy001]

A 12si or 10si couldnt definitely. A cs130, or especially a cs144 or a 15si could. But Just wire up the solenoid to the compressor and you'll just have to blip the throttle to allow the solenoid to pop out

[will e]

A 12si or 10si couldnt definitely. A cs130, or especially a cs144 or a 15si could. But Just wire up the solenoid to the compressor and you'll just have to blip the throttle to allow the solenoid to pop out

The problem is if the compressor cycles, so will the solenoid. So blip each time. I added a switch to control when the solenoid is engaged.

[kansasboy001]

Could wire it on a relay to the ac blower switch in series before the resistor that way when you turn on the blower regardless of speed setting or the compressor the idle will be bumped up.