97 xlt ac problem

[fishnbas2]

I have a 97 explorer xlt. With AC on and x idling the AC clicks and the rpms drop then about 2 sec later it clicks again and rpm rise. Iknow its cycling on and off but why is doing this. Is there a sensor bad or something?? I had the freon checked and all is ok. Im stumped.
Thanks

 

[shamaal]

It is the nature of the type of system used.

There is a pressure switch located on the accumulator that engages the compressor clutch. When engaged the compressor draws down the pressure on the evaporator side forcing forcing fluid through the orifice (vapor). This vapor expands in the evaporator sucking up heat. Eventually the pressure gets low enough that the pressure switch opens up. When it opens up, the pressure flows from the high pressure side to the low pressure side until it's high enough to turn the compressor on and it starts all over again.

The amount of time it takes to cycle is determined, for the most part, by the ambient temperature and the amount of airflow over the condensor and evaporator.

If it's cool and the refrigerant pressure's OK, relax and enjoy the cool breeze.

 

[Glacier991]

a 2 second cycle time is on the short side, in almost any condition except very cold ones. I am doubtful your refrigerant charge is adequate. A test of vent temps with adding a small amount of refrigerant and continuing until max cold is obtined is the only failsafe way to know, without recovering all charge and starting from scratch with a known quantity of refrigerant.

In other words, I still think you may be a tad low on charge.

 

[Techrep64]

By now I'm hoping you've found the answer to your problem. Unfortunately, mine has begun having a similar problem. 97 XLT. When in "Park" the A/C cycles continuously, I see the RPM dropping from about 750, to 500 or under and then the A/C kicks back off. If I maintain a higher idle, or have it in gear, the A/C seems to functions properly.

Any idea on what would cause that? My first thought is low coolant, but wouldn't it do it at higher RPM or in gear as well?

Thanks for the help,
Billy

 

[shamaal]

At the lower idle, the engine has less energy stored in the flywheel. At the higher RPMs there is more energy stored so that when the the A/C compressor kicks in the RPMs won't drop. To you, this means if you are judging that the compressor is kicking in by a downtick in RPMs at higher revs, it may be engaging you just don't see it.

Generally speaking, in hotter weather the compressor is more likely to stay on for longer periods of time due to the lesser energy transfer from hot air moving across the condensor. In colder situations the the condensor cools off faster and the refrigerant pressure drops faster. When moving the rush of air across the condensor also removes heat from the coolant transfer. That is why, the temp will drop another five degress at highway speeds than when you are idling. Other car manufactureres use a variable system that compensates across the temperature system. Ours is simpler but less robust.

Having said that, kicking in for only two seconds then out would most likely be a sign of a low refrigerant charge. I agree with G991's advice on the fix.