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A/C Problem Causing big MPG Drop

jeeperjohn said:
Does the A/C work? If the clutch fails it usually fails badly and quickly. Does the A/C compressor make noise when it's not engaged?
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The A/C Works Amazingly! And what do you mean the Clutch. What does that have to do with this? Sorry if I sound a bit novice...I am :dunce: And I am not sure about the A/C Compressor, I dont know what it would sound like
 
MXBoy11 said:
The A/C Works Amazingly! And what do you mean the Clutch. What does that have to do with this? Sorry if I sound a bit novice...I am :dunce: And I am not sure about the A/C Compressor, I dont know what it would sound like
Click to expand...


the clutch in question is the pulley on the A/C unit. the pulley freewheels until electrically activated to grab and spin the a/c compressor.
he was saying if the pulley is 'always on' then the compressor will fail quite noticably.

if your getting squeeling and bad milege, it could also be your water pump or steering pump.
simply turning the a/c on will change the load on the pulley's which could/would cause squeeling from one of the other pulleys if they are near dead.

depending how old those 2 pumps are, it could be helpful to change them out. the water pump is about $100, not sure about your steering pump... think about the same $100 tho. If milege is really bad, it could be worth your while to check those out too.

somewhat related;
when I had a bad t-stat but couldn't change it (4hour drive home at night) I easily wasted more money in gas than if I had bought a new t-stat the few tools needed and a lamp to change it in a parking lot.
 
beakie said:
the clutch in question is the pulley on the A/C unit. the pulley freewheels until electrically activated to grab and spin the a/c compressor.
he was saying if the pulley is 'always on' then the compressor will fail quite noticably.

if your getting squeeling and bad milege, it could also be your water pump or steering pump.
simply turning the a/c on will change the load on the pulley's which could/would cause squeeling from one of the other pulleys if they are near dead.

depending how old those 2 pumps are, it could be helpful to change them out. the water pump is about $100, not sure about your steering pump... think about the same $100 tho. If milege is really bad, it could be worth your while to check those out too.

somewhat related;
when I had a bad t-stat but couldn't change it (4hour drive home at night) I easily wasted more money in gas than if I had bought a new t-stat the few tools needed and a lamp to change it in a parking lot.
Click to expand...

Thanks! That is ALOT of help. Exactly what I was looking for
 
The A/C compressor pulley has bearings in it that allow the pulley to spin without turning the compressor when the A/C is off. If those bearings get dry and start to fail they will squeel or even make grinding noises when the A/C is off. This is a sign of impending failure. The same can be said for the bearings in the water pump and power steering as well as the idler pullies.
 
jeeperjohn said:
The A/C compressor pulley has bearings in it that allow the pulley to spin without turning the compressor when the A/C is off. If those bearings get dry and start to fail they will squeel or even make grinding noises when the A/C is off. This is a sign of impending failure. The same can be said for the bearings in the water pump and power steering as well as the idler pullies.
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Well there are no noises when the A/C isnt on as far as I know. There is one noise that almost sounds like an engine knock, but isnt (atleast I am pretty sure it isnt). It seems to have something to do with the belts, because I put belt dressing on them when I got it and that noise went away. I am just a kid and learning every day, so any other input would be greatly appretiated
 
Loosen the serp belt up, and check to make sure all pulleys turn freely. There shouldn't be any unusual noises, and the pulleys shouldn't have any real amount of side to side play.
 
Just to clear up one thing, in your first post you said you get noise when heat is turned on. Did you mean defrost? Normally you would not get any noise with the heat setting aside from noise from the blower motor if that is on its way out.

Is the squealing constant or just momentary when first turning on the A/C or heat?

What is your MPG? Poor mileage could be a completely different problem that the belt noise. And the squealing could be an aging and/or improperly tensioned belt. The noise going away with the belt dressing (a sprinkle of water will also serve to check this) suggests this as one possibility.
 
Pelican said:
Just to clear up one thing, in your first post you said you get noise when heat is turned on. Did you mean defrost? Normally you would not get any noise with the heat setting aside from noise from the blower motor if that is on its way out.

Is the squealing constant or just momentary when first turning on the A/C or heat?

What is your MPG? Poor mileage could be a completely different problem that the belt noise. And the squealing could be an aging and/or improperly tensioned belt. The noise going away with the belt dressing (a sprinkle of water will also serve to check this) suggests this as one possibility.
Click to expand...

It was the defrost. It squeals when I turn on the A/C or Defrost Heat within the first 5 minutes of driving or so. I can only pay for gas with cash, so I havent ever filled it up completely twice, but I have estimated it to be around 12-15 mpg. Usually right around 13. I heard I should be getting 18.

And yes the noise goes away when I put belt dressing on it
 
Whoa, missed the obvious. Get a Krikit II, and retension the belt, or if the belt is shiny on the flat side, or cracking on the ribbed side, replace it. If it needs replaced, I recommend dropping the extra coin on getting a good belt, as opposed to the cheaper belt.

If you do a lot of stop n go or city driving, 15 mpg isn't terribly low- when was the last time the plugs, wires, distributor cap and rotor, or filters were changed? Some specifics on your Jeep might help.
 
X2 - 13 is about right for city. Especially for someone who calls himself MX boy. Take a look at your belt. If it isn'g REAL bad looking, snug up the belt tension a little to see if it resolves your problem. If your AC is working good, you are probably OK. Usually a compressor will just freeze up and totally sieze when it goes bad. My 2000 gets 18.5 on a non-stop freeway trip at 80MPH, so don't expect that normally.
 
13mpg isn't bad for city at all. I get 13-15 just city and that's with high rpms due to my gear/tire combo.

~Scott
 
hubs97xj said:
Whoa, missed the obvious. Get a Krikit II, and retension the belt, or if the belt is shiny on the flat side, or cracking on the ribbed side, replace it. If it needs replaced, I recommend dropping the extra coin on getting a good belt, as opposed to the cheaper belt.

If you do a lot of stop n go or city driving, 15 mpg isn't terribly low- when was the last time the plugs, wires, distributor cap and rotor, or filters were changed? Some specifics on your Jeep might help.
Click to expand...
Yeah it is shiny. Sorry guys, I am new to vehicles. I just got my license and this is my first car. I am still a bit shy still. I have been around engines for a while and understand more than I used to.

Here are the specs:
1996 XJ
221K miles
Previously owned by a mechanic
Looks like it has 50k on it
Everything seems to have been replaced when needed, everything has checked out so far, and I have not had any major problems and I have put probably around 1000-1500 miles on it.

Sorry again guys, please just bear with me. I am still learning. You have to start somewhere right?

winterbeater said:
X2 - 13 is about right for city. Especially for someone who calls himself MX boy. Take a look at your belt. If it isn'g REAL bad looking, snug up the belt tension a little to see if it resolves your problem. If your AC is working good, you are probably OK. Usually a compressor will just freeze up and totally sieze when it goes bad. My 2000 gets 18.5 on a non-stop freeway trip at 80MPH, so don't expect that normally.
Click to expand...

Come on man, thats a low blow. Dont judge lol. It is a name that I have used for 4 years, so I just keep using it so I dont ever forget.

I do alot of stop and go driving usually, 5 minutes here, 5 minutes there. I think I am just not used to it because I am driving alot more lately.
 
Don't apologize! You capitalize where appropriate, use punctuation, form sentences and are articulate -- I don't know about the rest of the guys here but that buys you a lot of initial goodwill in my book....actually bloody amazing stop to think about it!

I don't know if you saw this thread:
http://www.naxja.org/forum/showthread.php?t=996074&highlight=mileage

Also a thread in OEM tech in the past week or so about improving fuel economy in a "stocker".
 
Pelican said:
Don't apologize! You capitalize where appropriate, use punctuation, form sentences and are articulate -- I don't know about the rest of the guys here but that buys you a lot of initial goodwill in my book....actually bloody amazing stop to think about it!

I don't know if you saw this thread:
http://www.naxja.org/forum/showthread.php?t=996074&highlight=mileage

Also a thread in OEM tech in the past week or so about improving fuel economy in a "stocker".
Click to expand...

Thanks I appreciate it! I am a part of many forums, and I agree with the punctuation comment. It is annoying and makes reading a post very annoying.

I didnt see that thread but I will check that out! Looks like some good information
 
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