A/C Cycle Time and Noise

Guys and Gals,
I have a 99 xj with ~60k. The ac still is quite cold but the compressor seems to be cycling a lot. On for ~20 seconds then off for only 6 to 8 then right back on again. On the highway it also seems to be making a louder hum than normal. I have also never changed the water pump but I have seen no leaks. I so have a light squeal from the belt at idle and my buddy thinks the idler pulley is going. I will replace the belt and pulley but should I look out for anything else? Thanks.

Tyler Forbes

I agree that belt and pulley are probably good insurance at 60k. While the belts off spin the water pump and see if it feels knotchy. If it's not leaking, and feels smooth, I'd leave it alone. Very possible that you are simply low on freon and that's causing the compressor to cycle. I think if it cycles a minimum of 5 times in a 1 minute period then it's low on freon (per the FSM). Hope this helps you.

-river

I have been told that rapid cycling like that is a typical symptom of low refrigerant, even if it's cold when it does cycle. It certainly was on my 99, and a couple of cans quieted it right down. edit: I forgot to add that when I put a gauge on it, when the refrigerant was low, the gauge cycled very high before it shut down, and this contributed to the noise. Once it was full, the gauge hung steady at a lower (but correct) level.

The rapid a/c clutch cycling could be just because the blower is on low or the blend door is not in the full a/c mode. High humidity will also cause that.
If I were you I would have it checked at a reputable a/c shop. You could do damage to it if you overcharge it.
Just my .02 Good luck, Rick

At idle, A/C on, coldest setting, fan on hi, if it cycles more then 5 times in one minute the freon is low. Add a SMALL can with dye in it, if it happens again in a few days or weeks take a black light and look in the drain coming thru the front of the firewall, right above the frame rail passenger side. If you see the yellow dye in the rubber hose it's your evaporator. This is a known issue, do a search on 'evaporator'. They sell a black light that looks like a pen with yellow glasses in a kit for like $8, handy item... You can also stuck a qtip in the drain and check that for color...

Guys,
Thanks for all the help. I will check he location of the belt on all of the pulleys and then the water pump for a bad bearing when I change the belt and idler. As far as the ac goes I know I have a bad blend door I believe. My defrost does not work due to the arm of the vacume linkage breaking off the blend door linkage. I brought it in to a dealership and showed the guy my defrost problem and he was like see that pile of blend doors, happens to every vehicle after about four years. Job is about $1000 to replace a $22 part. I havent done it yet. So you are saying I could be low on refigerant or could the defrost blend door be causing this problem? Thanks.

Tyler