Auto Air Conditioning & Heater Repair: a/c, r 134a, compressor clutch

Question
Mr. hill...
I noticed that the a/c system in my 1998 safari van was blowing hot air at full a/c/ power, then i decided to refill the system with r-134a kit. but as i  opened the hood, i found that the compressor clutch engages and disengages in intervals of about 5 seconds. what do you think is with the a/c/ system?

Answer
Adrian,
What your compressor is doing is what we call "cycling" In 99% of the vehicles with a cycling compressor the problem reverts to a low refigerant charge. A low refirgerant charge is of course caused by a leak somewhere in the system. The right thing to do is of course have your leak found, repaired, and then charged back up. But also, I am taking into account that apparently it has been working great since 98, so your leak is probably very small, therefore it would be extremely difficult to locate. My recommendation would be to go ahead and charge it back up. If it holds this charge for a good while... say the end of next summer or longer, I wouldn't worry about it too terribly much. If it leaks out again by the end of this summer, then defiantely have it found and repaired.

To explain what is happening so you can visualize it better...
Your compressor clutch engages and compresses and pushes refrigerant through the system. as the refrigerant hits your metering device a low pressure is created. These components are what creates your low side and high side of the system. Inside your low pressure line there is a pressure switch that is there to protect your compressor from extremely low pressures, as this will damage it.
Your compressor runs... your low pressure begins to drop. because of the low charge it drops too low, once it hits 17-22 psig in the low side line, the low pressure switch contacts open up shutting off the compressor. With the compressor off, pressure begins to equalize between your high and low sides, thereby closing your switch contacts and turning your compressor back on. And this continues to happen over and over again.

So, as I said, go ahead and charge it back up according to the directions on the kit you purchased. Once you do this, you should be riding nice and chilly again. I hope I was a little help in your understanding of what was happening, and finding a solution. If I can be of any more assistance in the future, do not hesitate to ask. Thank you for your question and good luck in everything.