Adding Compressor switch on 5.4
Thread Starter
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Senior User
Joined: Dec 2007
Posts: 325
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From: Lower Hudson Valley, N.Y.
Adding Compressor switch on 5.4
A while back, someone wrote about adding a switch that would turn the A/C compressor off rather than having it run in all setting [i.e. defrost, heat, etc.]. I want to get the best mileage that I can and, with winter coming again, was interested in comments on adding the switch, either through the fuse as the post had said [considering whether or not there are other things on the same circuit] or at the compressor itself. Also, what are your thoughts on whether it’s worth adding the switch or not.
Thanks in advance,
Later…
Brewster…
Thanks in advance,
Later…
Brewster…
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
I wouldn't, the A/C system also works with the defroster. It removes moisture from the air being blown on the windshield to reduce condensation. Most of the time, the defroster is all I need, so it wouldn't help me.
Sit. Stay.
Joined: Oct 2001
Posts: 18,308
Likes: 20
From: Washington State
I think the fuel consumption is negligible with the compressor running. IMHO, it is worth the few cents in fuel to make sure I can see out the windows without them fogging up.
Alas, if it something you want to do I would switch it at the fusebox and not the wiring under the hood...but that's just me.
Alas, if it something you want to do I would switch it at the fusebox and not the wiring under the hood...but that's just me.
Thread Starter
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Senior User
Joined: Dec 2007
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From: Lower Hudson Valley, N.Y.
On older vehicles, the defroster works due to the preheating of the air that it blows on the windshield. The A/C compressor and, resultantly, the dry air is not necessary to clear the windshield.
Also, my MPG goes from 12.4-12.5 to 10.1-10.2 during the summer on the same roadway with the A/C off then with the A/C on. In my experience, running with the A/C on uses more gas. I believe this is due to running the compressor off the engine.
MONSTA, you say you'd rather switch it at the fuse box. Why?
Thanks,
Later...
Brewster...
Also, my MPG goes from 12.4-12.5 to 10.1-10.2 during the summer on the same roadway with the A/C off then with the A/C on. In my experience, running with the A/C on uses more gas. I believe this is due to running the compressor off the engine.
MONSTA, you say you'd rather switch it at the fuse box. Why?
Thanks,
Later...
Brewster...
Tuned
Joined: Dec 2007
Posts: 338
Likes: 25
From: Hooterville, WI
True but it's also a much slower process. I drive a Metro daily for work which has no A/C ( or power steering for that matter) and it takes a long time for my windshield to clear up on a cool night. Your A/C dries the air blowing on the windshield, the drier air takes more moisture with it, instead of simply heating it to evaporation.
Thread Starter
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Senior User
Joined: Dec 2007
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From: Lower Hudson Valley, N.Y.
Maybe I should have rephrased my question... Any comments on the mechanics of switching the compressor on/off, either at the fuse box or at the compressor itself?
Later...
Brewster...
Later...
Brewster...
Senior User
Joined: Mar 2005
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I would be interested in this as well. I also see a 2 or more mpg drop while using the A/C.
My other thought was to by a shorter S-Belt and just bypass the compressor. Seeing how in Alaska I dont need A/C.
My other thought was to by a shorter S-Belt and just bypass the compressor. Seeing how in Alaska I dont need A/C.
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Senior User
Joined: Apr 2007
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mythbusters did a check on this. They ran the car around a track for several laps. One truck had the A/C on and the other had the windows down. There was almost no difference.
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Joined: Dec 2004
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From: Putnam Valley, New York
Compressor Cut Off
If you do keep the compressor off when it should be running, the PCM will think that something is wrong, and it will light up your check engine light and store a code. You will either have to scan it and erase the code or disconnect the battery to clear it. The PCM monitors the A/C system pressures.
RON
More Turbo
Joined: Jan 2005
Posts: 572
Likes: 37
From: Carthage, Mo
I have put a switch on almost every vehicle I have owned for the last 30 years. How can you NOT save fuel in a situation where the windows are up & there is less of a load on your engine? And I have replaced a few compressors in my time. If for no other reason, your are reducing wear & extending the life of your compressor. Windows fogging up a little? simply flip the switch. Don't forget to operate the compressor occasionally to keep the oil circulated in the system.
Sit. Stay.
Joined: Oct 2001
Posts: 18,308
Likes: 20
From: Washington State
Honestly? I think it's just easier to do. No snaking wires across the engine compartment through the firewall or splicing into the customer access. wires.
Up to you. Here's the A/C cycling switch that you would splice into under the hood.
I take it you already are familiar with the fuse box?
Up to you. Here's the A/C cycling switch that you would splice into under the hood.
I take it you already are familiar with the fuse box?
Sit. Stay.
Joined: Oct 2001
Posts: 18,308
Likes: 20
From: Washington State
ksCRUDE...dude, the second part of your user name certainly explains your spelling! 
What mileage tests are you referring to that have WORSE mileage with the AC off? Are taking into consideration drag caused by the windows being down?
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Some of you guys that are posting a near 20% drop in MPG when the AC is in use should get it checked out. The AC shouldn't be that much of a drag. (Pun intended)
What mileage tests are you referring to that have WORSE mileage with the AC off? Are taking into consideration drag caused by the windows being down?
```````````````````````````
Some of you guys that are posting a near 20% drop in MPG when the AC is in use should get it checked out. The AC shouldn't be that much of a drag. (Pun intended)
More Turbo
Joined: Jan 2005
Posts: 572
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From: Carthage, Mo
So you're trying to tell me ksCRUDE that if I was on a test track with my windows up, going the same speed, with the same wind conditions, the same temperature, humidity, etc, I will get better mileage with my compressor running & putting more load on my engine, which in turn means that the accelerator has to be depressed further to maintain the same speed, even if it is only 2% more of a load??? Hummm. I'm just not following the logic here. Maybe I should pull a 10k trailer around everywhere so I can get even better mileage. And don't worry, I DO have a real job.