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My 97 is beginning to leak in the A/C system. I've put two cans of the Autozone refrigerant through it this past year which isn't awful, but the second replenishment (performed yesterday) used an entire can of refrigerant. The gauge shows it falling off slowly until the compressor kicks off which takes about 15 seconds.
How long should the compressor be running before it clicks off? I assume it can't run the entire time or it would freeze up eventually, but how long would that be? I'm worried that if I leave it as is, all that on/off cycling will really beat up the compressor clutch and the compressor itself. My first inclination is to add another can of refrigerant but before I do I'd like to get an understanding of how the system should operate under normal conditions.
Second, I've never torn into an A/C system to replace seals but I'm thinking at 19 years old it may be time to do a permanent fix. What's involved? Are there special tools I'll need?
I can't let it go since the truck is almost exclusively used for towing to and from race tracks in the desert. A/C is a must!
You can't do any real AC repair with one of those kits you buy at Autozone. You need a real set of AC manifold gauges like this:
You need to know what the high side pressure is as well as the low pressure. Knowing just the low pressure (which is all those cheap kits tell you) without the high pressure is pretty useless. Also, those cheap gauges aren't necessarily accurate. You can't do any further diagnosis until you know the high side pressure and low side pressure PSI. Although if the compressor is cycling on and off every 2-5 seconds, it's pretty safe to say it's low on refrigerant.
If you want to replace all the seals, you need to first remove all the refrigerant from the system. Then you can start disconnecting things and replacing seals. When you're all done, you need a vacuum pump to to vacuum out all the air and moisture from the system before recharging. The only other special tool you'll need is a spring-lock tool to disconnect some of the AC hoses.
How fast the compressor will cycle is dependent on what fan setting you are on and also how hot or cold it is outside. Put the fan on high and the compressor should not cycle at all, assuming it is at least 60F outside.
But exranger06 is right, you need a proper set of gauges before you start thinking about tearing into it. HF gauges will do for your use.
Two cans in one year is way too much, you have an obvious leak. If you want to do the repair work yourself, at least take it to a shop and have them do a dye job and diagnose where the leak is. Good chance it's at the gauge fittings. Those schrader valves go bad over time.
If it's a slow leak, it's usually a fitting or valve that's gone bad, not something like the condenser, or evaporator.
