AC Cycling / secondary radiatior fan INOP

OK,

I seem to have two problems and am trying to see if thay are related, and how to fix them both, realted or not!

Vehicle:
2001 Cherokee Sport, auto
Just picked it up a couple weeks ago. Guy I bought it from claims he hasn't done any AC work, but the compressor looks new to me....

We test drove it just after a cold front came though.... with hail.... enough that the county trucks went out to clear roads.... love spring in NW Kansas.... so the AC seemed to work fine then... but may have not been doing all that much.

First issue:

When on max AC, the compressor is cycling apox every 10 seconds. It is blowing cooler, but not cold, air, and the lines condenser lines are getting hot and cold, as they should. Pressure-wise, It is running around 20psi on the 'off cycle', and over 90psi on the on cycle. (am working with a 'cheepo can gage'... will hook up to a good set of guages tommorow and see what I have both high and low side.)

Second issue:

The secondary cooling fan is not kicking on when the AC is on MAX. I have checked the fan, both at the fan conector, and by jumping the fan relay, and it works fine. I have also tested the relay, and it checks fine.

I have yet to have the Jeep heat up over about 195, so, it has never kicked on. (where is the sensor rhar trips that switch and will jumper that to check that circuit also?)

I can play with relay and make the fan come on for a second, and then it stops again. I will pick up a new relay tommorow, but it doesn't seem to be the problem to me.

My best guesses are either it's way over pressure (but I don't want to vent off all my system, just to prove me wrong, or there is a blackage in the system someplace...

(and how this all ties into the fan not working, I am not seeing, but see how both could be related..... )

Thanks for any ideas!

J

On the 01 the fan doesn't come on until the jeep is hot AND the AC head pressure is high.

It sounds like your system needs a charge, low side press should be 35ish IIRC it would be a good time to try some dye so that you can find any leaks present.

Once you charge up you will notice that once the jeep is hot AND the A/C is on it (the fan)works.





I didn't believe it myself until I read the schematic in the FSM.

NOTE: This is NOT true for all year models, 2000, 2001 for sure, 1997 definately not, anything in between IDK

that makes more sence. I had a 99 prior to getting the 01, so was troubleshooting the 'fan problem' for a 99. I knew there were several changes, but hadn't seen anything about the fan cycles up until now.

the 'quick on and off' with the fan, I am betting is a quick burst, built in so each time you go to AC or defrost, the fan is on a turn or so, just to keep it from locking up from lack of use in the off season.

Have gages in hand and will be looking at the AC issue later today. My first guess was I had a pressure issue, but things weren't making sence with the fan.

Will post what I find later

thanks for the info!

J

This previous thread may also help...

http://www.naxja.org/forum/showthread.php?p=856335#post856335