Living in the south it gets hot in the summer and its been in the 90s mostly so I run my ac pretty much all the time. That being said I was getting about 12mpg so this past week I decided to go without the ac and just roll my windows down. Im gettung about 17.5 mpg without ac. Is there something wrong with my compressor? Loose belt maybe? 5mpg jump just doesnt seem normal to me.

 

That does seem a little severe. I suppose first step is to loosen/remove the belt and see if you can rotate the compressor by hand. Shouldn't be effortless, but doable.

 

Following. I kinda had a little test myself judging by full tanks of gas as my gauge isnt accurate, I can go 320 miles on a single tank of gas with no ac but turn it on and i top out at 200 miles. I dont know if this is normal or not but thats 100 miles lost just in ac and i drive quite gently.

 

I see 14.5 MPG with the A/C on and 15.1 MPG with the A/C off and I usually fill up with a couple of gallons left in the tank.

 

The belt squeals on occasion when engaging the ac compressor. Im thinking it could be a loose belt or the compressor starting to seize, but I want a second opinion before I start throwing money at it.

 

how? Turn on ac then turn the jeep off and spin it? Otherwise id just be spinning the flywheel, right?

 

I don't think I thought that through. I don't have my jeep in front of me, but is there a bolt head on the front of the compressor clutch that can be used to rotate the compressor? With the clutch not engaged, and the motor not running, that should spin the compressor directly.

Also another reason for a compressor being very difficult to spin can be when the system is over charged. Is that a possibility in this case?

 

i dont believe its over charged. Its not blowing ice cold. My zj had colder ac and never had any real issue

 

i use my ac frequently and honestly hadn't noticed a difference in mileage. it basically gets 19-21 no matter what i do.

 

must be nice. Gas is almost 3 a gallon here so every mile counts.

 

I think the AC being -on- can touch the efficiency of your overall system in 2 ways.

1. Causing the motor to work harder by resisting movement on the belt path. You can check this.

2. Causing the motor to run poorly via some electrical issue caused by the extra demand that the electric fan, AC clutch coil, and interior blower fan put on the electrical system. You can check this as well.

 

I agree. I have seen a few magazine articles over the years where they did a comparison between running the AC and keeping the windows open, and it's never a big difference. They always wind up saying just run the AC and enjoying the comfort.

I'd throw a gauge on it to check the system pressure.

 

will a tire gauge work? Tried that with the fuel rail but it didnt fit and had to buy a special gauge.

 

No! Don't use a tire gauge! You need a special gauge for this.

It probably won't cost much to have it checked at a shop. It's free to call and ask.

 

will do. I think we have one at the shop.