intermittant A/C??

my 2000 xj has nice cold a/c for about 10 minutes then it blows warm air? If I shut off the a/c for 5 minutes it'll blow cold air for a bit again. I checked the level and the 134A is fine. The condenser is clean and clear. What other problem could there be?? The engine temps stay right around 210 and never go up? Any suggestions. Do you think a complete flush of the system and add new 134A will do anything, does 134a go bad or anything like that?

Thanks,
Mark

If the freon level looks OK, only a few things to shut it down. The thermostat, the high pressure switch or the low pressure switch. They´ve changed the setup over the years, but most of the new ones have a low pressure switch and high pressure switch.
With a set of gauges , you can watch and see if the freon is trying to operate out of the envelope or there is a thermostat or switch problem.
If you open the doors and turn the fan up full and it runs longer before shutdown, it´s an indication your thermostat is faulty or your freon is low.
If it shuts down quicker, it´s an indication that the freon is overfilled or there is air mixed in the system.
There are a few other strange things that can happen, the drain becomes plugged and the very cold water and/or ice messes with the thermostat, tells it it´s colder than it actually is.
There is moisture mixed in with the freon, that can plug up the system. When you turn off the A/C for awhile the ice blockage melts, until it forms when you turn on the A/c again, after a few minutes.
Hard to figure out exactly what the problem is without a set of gauges, a schematic and an ohm/voltage meter.

the compressor clutch could be bad, try this. next time it quits,probe the compressor lead with a tets light with the ac on if you have power there, then the clutch has gone bad, it just needs more amperage to run it and it isnt there.

Ok, checked for power on the clutch wire and there is 13.5 volts but the clutch does not engage.

The clutch will engage and the A/C will work for 15-20 minutes then it will stop blowing cold air and the clutch won't kick in. I checked the wiring while this was happening and there is still power.

Do clutches overheat and intermittantly work when they start to die? The local parts store wanted $250 for a new clutch and $300 for a new pump.

This is an '00 XJ, should I switch the pump since it's only another $50?

Can I just disconnect the hoses and reconnect them to the new pump or do I have to drain the whole system and then have someone refill?

Thanks guys, I'm heading on a 1600 mile trek next weekend and need to have the A/C figured out by then (along with many other problems!)

Mark

Before I´d shell out that amount of money, I´d try working the clutch with a jumper straight from the battery (carefull not to arch too much, might be a good idea to fuse the jumper). Make sure the ground is good. Voltage isn´t amperage, takes a lot of juice to engauge the clutch. Contacts could be a bit crispy in the relay, could be a cooked connector someplace.
Anything is possible, but all that´s really in the clutch is a big electromagnet, possible there is a bi-metal in there (doubt it). The next time it overheats, try an ohm test through the clutch to ground, if you have an open circuit it´s likely internal. If you know somebody with a similiar clutch, you can do an ohm test and compare the values. Possible the winding is shorted internally and it kind of works sometimes. Have seen the ground wire and the feed after the connector, get dinged/cut behind the clutch. Could be the wire is cut some of the way through.
Clutches don´t often go bad, most times it´s in the wiring.
Good luck with your A/C gonna need it soon. Got mine fixed. :yelclap:

you definately have a bad compressor clutch. now is it worth it for you to spend the extra $50 for a piece of mind. it is easier to replace the clutch and set the gap properly with the compressor removed. a new compressor is already set up properly.

i dont know how often the previous person works on cars, but if you have power to a component like that and it doesnt work that component is bad.the clutch grounds to the bracket that bolts to the block, so no real chances of having a poor ground

Whatever, nice to be so sure. Fixed a few cars, a few refirgeration systems, some industrial machinery, usually fixed more by troubleshooting, than I did by throwing parts at them. But that´s just me, did most of my work, where parts were hard to come by. Besides being some cheep.
If you look close on many compressors, there is a little wire coming from the clutch, bolted to the case (or the bracket) is the ring connector crimped or soldered, green or clean? Might be a ground?
My first Jeep was in 64, my second was about 2000 miles from the nearest dealer. The latest three, have seen a total of three or four shop visits in 26 years. Seems to work for me.

whatever works for you, i have been a factory trained jeep/chrysler tech for 17 years. i dont throw parts on cars. sometimes common sense prevails and just by experience i can diagnose problems like that relatively quick. if there is power to the clutch and it doesnt engage the clutch is bad.

jneary said:

i dont know how often the previous person works on cars, but if you have power to a component like that and it doesnt work that component is bad.the clutch grounds to the bracket that bolts to the block, so no real chances of having a poor ground

Click to expand...

Your probably right. Been awhile since I´ve been to school, Dodge trained me when you were about 3-4 years old. Guess I´m out of practice. But eager to learn.

eager to help, thats why i joined these boards.

The ground on the A/C pump wire is continuous (OC) with the negative on the battery and the positive (switched) wire to the A/C pump is a constant 13.5 volts whether the clutch is engaged (first 15 minutes of opperation) or disengaged after it overheats. There is no continuity between the positive and ground of the A/C pump eliminating the possibility of a short. There is a transistor between the + and the - of the A/C feed wires that I'm not sure the purpose of?? Either way, even when the A/C clutch fails to work it does not kick in if I apply a direct feed from the battery. It's definitely in the clutch.

Now, should I bring the jeep to an A/C shop to have the sytem drained before I disconnect the pump or will no coolant leak out when the hoses are disconnected. Same goes for after the new pump is in, do I need it professionally refilled?

Thanks,
Mark

If you just do the clutch you don't need to pull any hoses. If you replace the system as a unit clutch/compressor you need to have the system evacuated before you unbolt that hose on the compressor. Then change the component, take it back and have them draw a vacumn on it for anywhere from 10-40 minutes, depends on the A/C service devices efficency they are using and how much vac it will draw. Then you have it refilled with the correct amount of pag oil and 134a. I may be doing this tonight depending on how the refill goes, I think I have refilled mine too often using the 134a/oil cans that is has too much oil in it.
It has been a while but getting the clutch off the compressor can be a real PIA and usually requires a puller which can make it tough to do in the compressors cradle in the jeep.
The newer TJ's are even worse, they swapped the compressor and alternator locations, now the A/C compressor is down on the bottom and the alt is up top. Just noticed that on on a 03 I was working on a couple of weeks ago.
Positive outlook on that though is for those that play in alot of mud there is a way to move the alternator up top using the newer TJ brackets.

my problem turned out to be the clutch. I got a deal on a new clutch from a friend who works at a dealer. The clutch was very easy to change. It took about 20 minutes and 10 of those minutes was spent looking for my gear puller. The A/C stays running now and the jeep gets icy cold! :roll:
Thanks for the advice guys!

You are now our resident, A/C clutch expert :helpme: I expect, some posts helping the other guys out, with there A/C clutches. :thumbup:

really quite easy.

1. Remove the outer nut on the end of the shaft before you remove the belt. Simply unplug the compressor, connect the wire from the compressor to the + of the battery to engage the clutch and use the belt tension to hold the pulley while you remove the nut. If the clutch won't engage at all then jam a screw driver in there somewhere to stop it from spinning.

2. Remove the belt.
3. Remove the 4 bolts holding the compressor down.
4. Place the compressor somewhere within hose reach that makes it easy to access the face of the pulley.
5. Remove the outer plate with the splines (pry off with a screw driver)
6. Remove the 1st snap ring.
7. Use a gear puller to remove the outer pulley.
8. Remove the small screw & clip holding the wires down.
9. Remove the 2nd snap ring.
10. Use a gear puller (if required) to remove the coil assembly.

11. Replace in opposite order of removal. Coil assembly, large snap ring, screw & clip, outer pulley, small snap ring, splined outer plate, 4 bolts, belt, nut.

12. Taa Daa, all done!

Question? On the old coil, is there a bi-metal wired in there, looks like a little light bulb? Actually kind of a thermal fuse. Sometimes tucked into the winding a bit, mostly near the input wiring. Sometimes at the end of the + wire in a shell of some type. Just curious, sometimes they are in there sometimes not.