Should we disable the AC compressor?

Mykol · **Posted:** Fri Feb 09, 2007 10:41 pm

In the interest of improving fuel economy, do ya'll think it is advisable to consider disabling the air conditioner compressor? I would think this could be done by placing an in-cab toggle switch in the power wire to the compressor. It seems like I can hear mine cycling on/off in nearly every climate control selector position. Any thoughts?

CATCRD · **Posted:** Sat Feb 10, 2007 12:00 am

I took the dash apart to tape over the contact that turns on the a/c automatically when you have it in defrost modes. Those are the only two modes where it comes on without pressing the a/c button. I got the idea from a writeup somewhere on this site.

Metal Man · **Posted:** Sat Feb 10, 2007 1:00 am

The A/C also runs in the floor position.

ATXKJ · **Posted:** Sat Feb 10, 2007 10:05 am

There was an old thread that had instructions on disassembling the control panel and removing the contact strip that controls the compressor for the floor level

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=6042&highlight=compressor+settings

litton · **Posted:** Sat Feb 10, 2007 10:13 am

Doesn't the little button turn it off?

oldnavy · **Posted:** Sat Feb 10, 2007 10:17 am

litton wrote:

Doesn't the little button turn it off?

I seem to remember it run in all positions except the floor position, or at least that is how ours seems to work.

BVCRD · **Posted:** Sat Feb 10, 2007 10:19 am

Why bother? We are talking0.000025 mpg..............MAYBE.

oldnavy · **Posted:** Sat Feb 10, 2007 10:24 am

BVCRD wrote:

Why bother? We are talking0.000025 mpg..............MAYBE.

Yes the only real way to have a MPG increace is if are very anal retentive and track every purchase of fuel over long periods like a year or more. Average person can not track a 1 mpg increase or decreace.

tulsa · **Posted:** Sat Feb 10, 2007 10:25 am

I have been told it is a good idea to run the compressor for a few minutes every couple of weeks to keep the seals in good shape.

BVCRD · **Posted:** Sat Feb 10, 2007 10:28 am

oldnavy wrote:

BVCRD wrote:

Why bother? We are talking0.000025 mpg..............MAYBE.

Yes the only real way to have a MPG increace is if are very anal retentive and track every purchase of fuel over long periods like a year or more. Average person can not track a 1 mpg increase or decreace.

Exactly. Throw in different start up outside air temps, and other variables, and you fluctuate even more. I had an '02 Ranger that I traded in on the KJ, and when that thing kicked on, if you weren't under throttle, you felt it and it was though you ran over a road gator. :lol:

It really sucked the power down but not with our little jewels.

Stan Wright · **Posted:** Sat Feb 10, 2007 1:41 pm

I would think a good way to increase mileage would be to install locking hubs on the front, if it's even possible. Just pondering.

oldnavy · **Posted:** Sat Feb 10, 2007 2:03 pm

Stan Wright wrote:

I would think a good way to increase mileage would be to install locking hubs on the front, if it's even possible. Just pondering.

They were not the big MPG saver as you would think, and with the higher mantainance of having to repack every year or two depending on what driving conditions you were in, $40 a hub got expensive and the auto locking I think were problematic due to high torque at hub on early models and servicing was a little more expensive. Seen more the one 4x4 sitting on the side of the road with hub failure back in those days.

RFCRD · **Posted:** Sat Feb 10, 2007 2:09 pm

Just love how a little cold weather brings out the "if I do this, I can squeeze the N'th degree out of my fuel" crowd. If you want to improve your fuel economy, move someplace warm.

Let me clue you in on fuel economy, especially with electronic controlled, charged-air cooled diesels. Cold weather will kill your economy. Diesels don't like to burn cold diesel fuel or suck sub-zero cold air. These engines already tend to run on the cold side for a diesel and won't be helped much by overchilled charged-air. Only a hunch with the computer logic but the computer may be keeping the EGR open longer in extreme cold weather to rewarm the intake air (remember that clogged MAP sensor in the intake manifold?). An open EGR valve will have a dramatic negative impact on fuel economy.

BTW, my last two tanks of fuel only got me @ 20 mpg running expressway miles in -5F to 5F degree weather, mileage that I would consider poor by CRD standards (ie, burning 20% more fuel). Rather than disconnecting your A/C, you would likely do better to use your block heater to cut your warm-up consumption.

DarbyWalters · **Posted:** Sat Feb 10, 2007 3:25 pm

oldnavy wrote:

BVCRD wrote:

Why bother? We are talking0.000025 mpg..............MAYBE.

Yes the only real way to have a MPG increace is if are very anal retentive and track every purchase of fuel over long periods like a year or more. Average person can not track a 1 mpg increase or decreace.

If you can't track it, is it there? I do feel mine cutting on and off in the floor position when sitting at a light idling.

BVCRD · **Posted:** Sat Feb 10, 2007 3:36 pm

DarbyWalters wrote:

oldnavy wrote:

BVCRD wrote:

Why bother? We are talking0.000025 mpg..............MAYBE.

Yes the only real way to have a MPG increace is if are very anal retentive and track every purchase of fuel over long periods like a year or more. Average person can not track a 1 mpg increase or decreace.

If you can't track it, is it there? I do feel mine cutting on and off in the floor position when sitting at a light idling.

I don't have a clue what I'm talking about here, but just say the thing burned 1 gallon more fuel per tank, which no way it does, but just say. So that is like 5%. So 5% of 24 MPG is 1.2 mpg...... 1.2 mpg decrease because the thing is cycling on and off. And remember it ain't using 1 gallon so it is less than that.

oldnavy · **Posted:** Sat Feb 10, 2007 4:09 pm

BVCRD wrote:

I don't have a clue what I'm talking about here, but just say the thing burned 1 gallon more fuel per tank, which no way it does, but just say. So that is like 5%. So 5% of 24 MPG is 1.2 mpg...... 1.2 mpg decrease because the thing is cycling on and off. And remember it ain't using 1 gallon so it is less than that.

Say what???

BVCRD · **Posted:** Sat Feb 10, 2007 4:18 pm

oldnavy wrote:

BVCRD wrote:

I don't have a clue what I'm talking about here, but just say the thing burned 1 gallon more fuel per tank, which no way it does, but just say. So that is like 5%. So 5% of 24 MPG is 1.2 mpg...... 1.2 mpg decrease because the thing is cycling on and off. And remember it ain't using 1 gallon so it is less than that.

Say what???

What's the matter? Can't you do squirrel brained math??? Told you I didn't have a clue. Just rambling. Bottom line I was trying to get across was the AC isn't using mush fuel.

CATCRD · **Posted:** Sat Feb 10, 2007 4:32 pm

Metal Man wrote:

The A/C also runs in the floor position.

Edit: you're right, did it so long ago I fogot, but I disabled it in floor and flr/def, leaving defrost alone.

Besides running the a/c when I don't need it and wasting fuel (however little, I don't care) what I object to is the manufacturer assuming I'm to dumb to decide when to have a/c or not.

This is what I followed, including the zero speed #4.

http://jeepkj.com/forums/viewtopic.php?t=1265

MrMopar64 · **Posted:** Sat Feb 10, 2007 7:43 pm

RFCRD wrote:

Just love how a little cold weather brings out the "if I do this, I can squeeze the N'th degree out of my fuel" crowd. If you want to improve your fuel economy, move someplace warm.

Let me clue you in on fuel economy, especially with electronic controlled, charged-air cooled diesels. Cold weather will kill your economy. Diesels don't like to burn cold diesel fuel or suck sub-zero cold air. These engines already tend to run on the cold side for a diesel and won't be helped much by overchilled charged-air. Only a hunch with the computer logic but the computer may be keeping the EGR open longer in extreme cold weather to rewarm the intake air (remember that clogged MAP sensor in the intake manifold?). An open EGR valve will have a dramatic negative impact on fuel economy.

BTW, my last two tanks of fuel only got me @ 20 mpg running expressway miles in -5F to 5F degree weather, mileage that I would consider poor by CRD standards (ie, burning 20% more fuel). Rather than disconnecting your A/C, you would likely do better to use your block heater to cut your warm-up consumption.

Actually, in the very cold ambients the EGR is actually shut off until the engine is completely warm. This is due to condensates which will form in the EGR pipes after the cooler and then clog the intake. Also, more EGR will increase the fuel economy and allow the engine to burn cleaner (cuts down NOx formation). There are corrections in the SW to adjust the fuel quantities based on ambients, EGR %, etc. etc. A lot of fuel mileage decrease is due to the winter blended fuel.

Additionally, the A/C compressor draws about 15-30 N-m of torque depending on temp and head pressure. The ECU adjusts the fueling through a PT1 filter (software) such that you hardly feel the AC kick on/off. In the emissions test chamber it's about 1.3-2.0 L/100km difference in economy with the A/C on (worse economy, of course) - so turning it off if you don't need it is a good thing. If you don't want it on, unplug the connector from the compessor.

BVCRD · **Posted:** Sat Feb 10, 2007 8:07 pm

MrMopar64 wrote:

RFCRD wrote:

Just love how a little cold weather brings out the "if I do this, I can squeeze the N'th degree out of my fuel" crowd. If you want to improve your fuel economy, move someplace warm.

Let me clue you in on fuel economy, especially with electronic controlled, charged-air cooled diesels. Cold weather will kill your economy. Diesels don't like to burn cold diesel fuel or suck sub-zero cold air. These engines already tend to run on the cold side for a diesel and won't be helped much by overchilled charged-air. Only a hunch with the computer logic but the computer may be keeping the EGR open longer in extreme cold weather to rewarm the intake air (remember that clogged MAP sensor in the intake manifold?). An open EGR valve will have a dramatic negative impact on fuel economy.

BTW, my last two tanks of fuel only got me @ 20 mpg running expressway miles in -5F to 5F degree weather, mileage that I would consider poor by CRD standards (ie, burning 20% more fuel). Rather than disconnecting your A/C, you would likely do better to use your block heater to cut your warm-up consumption.

Actually, in the very cold ambients the EGR is actually shut off until the engine is completely warm. This is due to condensates which will form in the EGR pipes after the cooler and then clog the intake. Also, more EGR will increase the fuel economy and allow the engine to burn cleaner (cuts down NOx formation). There are corrections in the SW to adjust the fuel quantities based on ambients, EGR %, etc. etc. A lot of fuel mileage decrease is due to the winter blended fuel.

Additionally, the A/C compressor draws about 15-30 N-m of torque depending on temp and head pressure. The ECU adjusts the fueling through a PT1 filter (software) such that you hardly feel the AC kick on/off. In the emissions test chamber it's about 1.3-2.0 L/100km difference in economy with the A/C on (worse economy, of course) - so turning it off if you don't need it is a good thing. If you don't want it on, unplug the connector from the compessor.

In squirrel brained language please. How much additional fuel would be used out of a 20 gallon tank by leaving it on and driving say,,,,,,,,,30 mph for a total of 13 hours?

Should we disable the AC compressor?

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