'99 Grand Cherokee A/c Question

[DCAP63]

Whether or not I'm running my A/C, when I turn the car off and look under the hood, I see the high pressure hoses to the A/C compressor are sweating alot. They already have some surface rust them. Is this normal? Thanks
Dave

[DIY Mechanic]

What you are seeing is an example of the Dew Point.

This is the same thing as setting a COLD bottle of soda outside on a humid day. The bottle will start to sweat and drip on your shirt when you go to take a drink.

Moisture in the air is condensed out when it is exposed to a cold source that is at or below its dew point.

R134A boils at 13 degrees Fahrenheit at atmospheric pressure.
The liquid line of the system has liquid refrigerant that is at a temperature below the Dew Point for the day.

Since the air is Dry – Less Humid in the winter, you usually do not see this effect in the winter.

[DIY Mechanic]

I just reread you post. The tubing is Aluminum, you must mean the hose clamps. This can be a problem over time but these hoses can be repaired/replaced without going to the dealer. I would not consider this a major problem but I would keep an eye on it.

[richpinkham]

I have a 99 grand limited and it too does the same thing but I found the A/C compresser running even when the controls are set to OFF. Asked Jeep dealer about this and their answer was that the controls should be set to AUTO... Not what I wanted for an answer. Still trying to find someone that knows why it runs even when not sopposed too

[fdrepairshop]

alot of g/c a/c control heads are shorted internally, i have replaced countless amounts of them whether hey are dual climate or manual. expensive fix but may be your problem.