air conditioner shooting at me

[91CheapExp]

The AC on my 91 explorer, 116,000 miles, worked ok when I bought it. Not great, but okay. One day while working under the hood with the engine running and AC on, there was a sudden series of small sputtering explosions like little firecrackers. There appeared to be puffs of vapor to the right (drivers' perspective) side of that throttle cover on top of the engine. I thought maybe an AC pressure relief valve, cuz I was setting up the control for my electric engine cooling fan conversion. The loud noises happened on 2 occasions. I put a fan control thermostat on the condenser and set it so the fan starts up as soon as the condenser is warm to the touch.

Went to an AC shop to check for leaks incase I had busted something. This 'expert' had a lot of answers and immediately started recharging the system. Check for leaks? Nahhh. By now, AC was nonexistent, with inside vents putting out 78F. He charged for awhile, no change in temperature, (electric cooling fan running great all the time), suddenly bang bang bang. "OH, is that the sound you were talking about?" he said after he returned from cleaning his pants. "Bad compressor. Get a new one and come back in here and then I'll convert it to 134A for you. If it popped like that several times, that's how you lost your charge."

So I'm sitting around wondering why a bad compressor builds up enough pressure to make some relief valve pop. Whatever the popping is, it's got a lot of pressure! Any opinions? something blocked? what could I have damaged when running the AC without sufficient condenser cooling? Or just coincidental timing? Spend all the money to convert to 134A? best place to buy a compressor? incidentally, the 16" fan is doing a great job now that I have it controlled right.

thoughts, comments appreciated.

J

 

[mrboyle]

Most likely what was happening was there is a blockage in the system(probably the oriface tube plugged up w/ debris from the failing compressor) and as the genius was adding freon it was not circulating, instead it was building up pressure until the high pressure exceeded the sealing ability of inr of the o-rings in the compressor, and the system vented. You asked if it was worth the money to convert to 134A, considering R-12 is currently selling for aprox. $70 per/lb. and 134A is $9-$10, I'll let you do the math.