Jassack

iTrader: (2)

ok so heres the problem. every time i turn my ac on my engines revs up probably a good 200-400 rpm and im wondering why it does this and if i can make it go away somewhat.

Toehead

It is supposed to do that. The ECM kicks up the idle to compensate for the load the compressor puts on the engine. Does your ac work?

Jassack

iTrader: (2)

yea it works. its just really noticeable. it JUMPS from about 200-400 though and i didnt think that was right.

Toehead

Maybe somebody with working AC can chime in and tell the man how much it's supposed to jump.

Reid Fleming

iTrader: (2)

What are the actual RPM's that it starts and finishes at? (when turning on the A/C)

Is this when you're first starting the car or after it's warmed up?

Jassack

iTrader: (2)

i'll get back to you on what rpm it starts and stops on but it does it all the time even after its warmed up. and it keeps clicking on the compressor like every 5 seconds when i have the ac on. im pretty sure its not supposed to be doing that so often

Toehead

It cycles rapidly when you are low on charge.

Jassack

iTrader: (2)

ok it jumps from about 600 to 1000 rpm and thats only when im stopped. By low on charge you mean? How do you fix it?
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sorry if i seem a little uneducated on this i just dont know much about ac and it doesn't seem to me like it should be doing it as often as it does. thanks for being pacient though

northeaster79

mine in my firebird runs up about 300rpm when the ac cycles,it compensates for your compressor load,and your alternator load for your fans.

Toehead

By low charge, I mean that you are low on refrigerant in the AC system. It cycles often to keep the system from "icing"

Russ-So Cal

You have a low refrigerant charge. You may have lost refrigerant through the shaft seal by not running the a/c in winter. The seal is made by the oil that is pumped up between a polished carbon ring and a polished steel plate. If the compressor does not cycle on at least once a month or so, the oil wil run off and you will lose part of your charge. When you run your defroster, the system is designed to turn on the a/c compressor so that it runs the heater and da/c at the same time. This is to keep oil on the shaft seal in winter and to remove the moisture that is removed from the windshield from within the car. You have low pressure switches in the system designed to protect the compressor from running without refrigerant in the system. Your problem may also be a slow leak in the system that needs to be repaired. If that is the case, you will eventually loose all cooling power in the a/c and the compressor won't cycle on at all.

The engine is supposed to go to a high idle when the a/c is turned on. With a full charge, It won't idle as fast as you are seeing now because you will be running a discharge pressure in the compressor between 200-250# and the compressor will bog your engine back down to somewhere around 800-900 rpm. Without the proper charge of refrigerant in the system, the compressor is not putting a load on the engine, but high idle is controlled by a solenoid that just pulls in regardless of whether there is extra load on the engine or not.

If you still have r12 in the system, you will need to take it to an a/c shop for repair unless you have a recovery system and a federal license to recover freon. Without the license and recovery system, you can't legally buy r12. Also the price of r12 is going to be somewhere around $20.00 per pound +/- and the minimum size container available is 15#. The retail price from a shop will probably be somewhere between $30.00-$50.00 per pound. Before I retired, freon prices changed at least 3-4 times a year.

Jassack

iTrader: (2)

So what your saying is i need to go to a ac place and get r34 put into my car if i dont have it and tell them to fix whats wrong? How much you think it will cost?

scooter500

iTrader: (1)

they sell a/c in cans w/ a pressure gauge already attached at parts stores for about $20 a can. might try that

Toehead

Only problem is that is R-134A, made for newer cars... He needs the "good stuff" R-12, unless he wants a conversion, which is basically a flush and a new orfice tube, and orings, and maybe hoses.
The oil made for r-12 is not compatible with 134a and reacts badly, forming acids which attack the compressor.

84 1LE

iTrader: (9)

There are kits on ebay for a freon alternative called "freeze 12".Its suppose to be combatible with all A/C systems.It seems like a much btter solution to R134!Maybe somebody here has used it already.

Toehead

I have used a hydrocarbon version with very good success. It requires no retrofit or flush at all.