AC idle advice

Sonny said:

Don’t know the ounces, but filled it till the gauge was in the green/full zone.

Did not evacuate. All new parts. Is it required?

AC was on the 318 2 barrel. Swapped for a 360 4 barrel. Would think thats enough engine.

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Its not a matter of having enough engine, its that there is more demand put on the engine at idle, so, a idle solenoid is used on stock applications to increase the idle speed when the AC is on by actuating the plunger the throttle shaft is not allowed to return to regular idle position. Here is a picture of an AC idle solenoid on my 73 340 RR, this is on a thermoquad carb, and is attached to the AC circuit, so it engages when the AC is switched on.

That's very interesting.

My unmolested 73 318-2 A/C car does not have an A/C idle solenoid (nor does it have a clutch fan or coolant reservoir).

However, the FSM lists different idle speed settings for A/C and non- A/C 318 cars.

YY1 said:

That's very interesting.

My unmolested 73 318-2 A/C car does not have an A/C idle solenoid (nor does it have a clutch fan or coolant reservoir).

However, the FSM lists different idle speed settings for A/C and non- A/C 318 cars.

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I have all three plus a 28" radiator, yes I said 28" radiator, that was factory for the max cool options on the 340.

YY1 said:

FSM spec is different for AC and non AC cars.

I want to say my 73 calls for 50 RPM increase.

Mine is at 700 and is fine with the clutch not engaged, but does drop 50.

I've been harvesting solenoids and hook up should be easy (just tap the clutch lead) but mounting looks like it's going to be fun.

Plus it's kind of hard to tell the diff between an AC solenoid and an idle stop.

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The new style Sanden compressors don't put near as much drag on the engine as the original ones did. I just set my idle today at 800 in park and 750 at idle with the AC on.

bearman said:

Jim what are the pressures reading at 30%less. That is interesting that it will do what you want running with less. I have done it both ways and came out with larger load working best. But doesn't mean I'm correct in my thought pattern

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In my opinion, the amount of refergant in the system is directly proportional to: operating pressure (evaporator), condensing pressure (relating to air temperature entering the condenser) and the SPECIFIC HEAT CHARACTERISTICS of the refergant. Specific heat is the refrigerant's ability to absorb and release heat. In a refrigerant system (car's AC system).....it does NOT MAKE COLD but REMOVES HEAT.
According to Boyle's Law, system pressures, temperatures and volumes are inter related....pressure varies directly with temperature and inversely to volume.
Bob Renton

bearman said:

Jim what are the pressures reading at 30%less. That is interesting that it will do what you want running with less. I have done it both ways and came out with larger load working best. But doesn't mean I'm correct in my thought pattern

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The 30% is just repeating what Classic air states. I can't tell you how much R134a I have in my Coronet, I just use pressure to set it as I stated. I have not spent the time to do it "right" based on your suggestions though.

Jim

JimKueneman said:

The 30% is just repeating what Classic air states. I can't tell you how much R134a I have in my Coronet, I just use pressure to set it as I stated. I have not spent the time to do it "right" based on your suggestions though.

Jim

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Thanks Jim when you get the time please give me a heads up. I am working on an idea of putting in a sub cooler and just gathering info for all my thoughts.

bearman said:

Thanks Jim when you get the time please give me a heads up. I am working on an idea of putting in a sub cooler and just gathering info for all my thoughts.

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RJRENTON said:

In my opinion, the amount of refergant in the system is directly proportional to: operating pressure (evaporator), condensing pressure (relating to air temperature entering the condenser) and the SPECIFIC HEAT CHARACTERISTICS of the refergant. Specific heat is the refrigerant's ability to absorb and release heat. In a refrigerant system (car's AC system).....it does NOT MAKE COLD but REMOVES HEAT.
According to Boyle's Law, system pressures, temperatures and volumes are inter related....pressure varies directly with temperature and inversely to volume.
Bob Renton

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you are correct in the boyles law and that's what I am doing. For the most part I'm gathering info of temp vs pressure and heat vs cooling. Fan timing vs pressure etc.a/c is a simple hot over cold a how it takes place the pproblems that people think more is better and then you have people doing what is done on a daily basis not maintaining or don't know how the system works. That's why this forum is so good the knowledge that is expressed and the help that each one of us gives out. For me its s learning tool not just for my project but for my work also. On me of the biggest problems that I run into is at the condenser not getting the temp drop across it so when it hits the expansion valve it doesn't have to work so hard to get the vapor into a cool gas. It could be from fan speed or clogged condenser not being cleaned air in the system or a pressure switch not turning on at the right time.So like I was saying gathering info from different people and getting it right.

Some experience to share with my stock ac in the 318. I have added 134 A in 2010 and I cannot believe it s still in there. The original hoses have been removed to install the new o rings, a new dryer was installed also. The temp out at the vent on a 85 deg. day is below 45 deg. it will drop even more on occasion I have not installed a capillary tube relay for the compressor. I have a thermometer in the vent and watch it if it gets close to 40, I just turn off the compressor switch on the dash so I wont have a freeze up. Some fittings at the old hose ends have oil residue. Its a leak but every year it works! I run the compressor now and than during the warmer winter months when I start it up for circulation when it is off the road for the 5 months here in Massachusettes. After 45 plus years and only replacing the dryer, o rings and removing the epr valve from the compressor I think I am doing pretty well. I want to keep the original look under the hood that is why I wont have the ac hoses rebuilt for now.