Surge

[timlubbers]

My 4.0L 2000 Cherokee Sport surges and A/C kicks on for about 1 second when the controls are in defrost ( windshield ) setting with temp set cold. It doesn't do it with controller turned to off position. Surge is from idle 800 rpm to about 1000 rpm.

[Mudderoy]

My 4.0L 2000 Cherokee Sport surges and A/C kicks on for about 1 second when the controls are in defrost ( windshield ) setting with temp set cold. It doesn't do it with controller turned to off position. Surge is from idle 800 rpm to about 1000 rpm.

Does you A/C cool? Sounds like the A/C compressor kicking on then the low pressure switch kicking it off.

[4.3LXJ]

The defrost will kick on momentarily in defrost on that model. It is used to dry the air going to the windshield. X2 on whether or not the AC is operating properly

[timlubbers]

Thanks. Sounds like normal operation only in defrost. Thought that might be the case, but good to get confirmation. A/C works fine except it doesn't blow cold because I have a slow leak somewhere.

[BlueXJ]

Determine the leaks location,fix it, then recharge and let us know how it is working to cool the Jeep.

[gary63]

you may have a small vacuum leak if it idle at 800 and goes up to 1000 I have a 2000 too mine idle in the med 600 and when a/c is on goes up to the med.700 your sound like it may be running alettle fast.

[BlueXJ]

When checking for a vacuum leak dont forget the manifold bolt where it attaches to the head. They need to be tightened as a yearly maintenance item.

[Mudderoy]

When checking for a vacuum leak dont forget the manifold bolt where it attaches to the head. They need to be tightened as a yearly maintenance item.

I did NOT know this! :bang:

[BlueXJ]

I did NOT know this! :bang:

As the gasket is compressed and loses it's elasticity from age and heat, plus the vibration of the engine the gap increases and on my maintence log I check those bolts yearly. Each year in the 12 years I have owner this particular XJ the bolts usually have at least one which requires re-tightening.

[timlubbers]

Compressor was bad. Now that I have replaced it , I'm told I need to add 6oz. of oil before I charge it. Does that sound right ?

[4.3LXJ]

Yes

[timlubbers]

Thanks.