Cold Air when HVAC switched to Bi-level

[Ranger Dick]

This has me very confused. It finally warmed up and as a result I turned my thremostat all the way to the left (most Blue) while the selector was on Bi-level (Vents and floor) this is the position just to the right of the a/c snowflake. It was about 80 degrees outside but the air coming out felt like the a/c was on. When I then moved the switch to one notch to the right the air warmed up to what I would consider to be regular outside air. When I went back to Bi-level, the air got cold again. Is my A/C unit operating when it shouldn't be? To verify this, I tried it on my work truck 01 2500 gasser 4x4 and it appears to do the same thing. This might be causing poor fuel mileage for those who drive with the bi-level position alway on, Like I have since I got the truck. Since the A/c unit doesn't step up the idle, I can't tell for sure. Sorry about the length of the post.

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01. 5 ETH/DEE QC, 2500 4X4, 3. 54 Everything but leather

 

[Wiredawg]

It has been my experience that the AC comes on anytime you turn the dial over into the blue regardless of the vent setting. I'm thniking about finding the lead that controls turning on the compressor and intstalling a separate switch.

My '96 has a separate switch to select AC or just fan.

Wiredawg

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2000 4X4 SLT QC 8' bed; 6 spd, 3. 54 ; BD exhaust brake and 4" exhaust syst; TST PM2; Airlift Super Duty rear air bags; RS 9000 shocks; pyro/boost gauges in 2 gauge a-pillar mount; back preasure gauge mounted under dash; KN air filter; Brown's Welding brush/grill guard, rear bumper & headache rack; nerf bars and aluminum roll top rear cover, Warn front receiver and Hadley air horns, 20K Reese hitch,Mag-Hytec dif cover,Psycotty Air.

 

[ducman]

in the owners manual i think it show's a snow flake on bi level but i can tell you for sure the first three positions are for a/c. one thing i miss about imports is that you can control the a/c manually . if anyone has figured out how to do this please post it . thanks tony b

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98 1/2 2500 4x4 standard cab long bed american eagle 16x8 no muffler roll pan was driftwood now 2000 galaxy blue after $12000. 00rear end job. rhino liner ,ram brush guard &nerf bars

 

[Ranger Dick]

DOH!!!. Sitting at work, pulled the owner's manual and it states that "bi-level" position is for Bi'level A/c. But there is no snowflake. I would guess that its been worth about 1 mpg for the past six months. Stupid me. Yeah, I would sure like a separate A/C switch and also a position where you can get outside air without running the fan. Guess the moral to the story is when in doubt read the book.

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01. 5 ETH/DEE QC, 2500 4X4, 3. 54 Everything but leather

 

[dabubba]

yes you're right- It's just a dc kinda thing #ad
your ac also comes on in defrost mode too- my '99 did it and my '01 does it too- I guess its for the midwest/south where you get some humidity-

 

[Evan A. Beck]

ALL of the 1998 12 valve trucks I have worked on have the snowflake in the bi-level position. Strange, huh? #ad

 

[illflem]

Here's the link for disableing the AC in defrost on pre '98s. Fritz said he was looking into the best way for newer rigs.

I was wrong, the link now has info for newer rigs at the bottom, thanks Dave


[This message has been edited by illflem (edited 03-23-2001). ]

 

[Big-D]

Thanks to you also Bill for providing the link. Now I can accomplish what DC engineers should have installed for us all along.

 

[joel]

My understanding of the AC is that anytime you select a 2 vent position or the defroster, the AC compressor will engage. This is partly to ensure the compressor gets cycled regardless of the climate to ensure the seals don't dry out. If you want just ambient air, you have to pick one of the single vent positions.

 

[illflem]

What I'd like to do even more than disable the AC is to have fresh unheated outside air come out the dash vents while heated air comes out the floor vents. One of the things I loved about my old Toyota...

 

[Archive]

FWIW, I have not noticed any difference in MPG from winter to summer driving with the AC. Here in Phoenix, the AC is pretty much always on from late April to October. Year round commuting to/from work is always 19. 4 mpg.

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'99 4x4, SB, QC, 3. 54, LSD, AT, Leather, Mag-Hytech, Westach Guages, Line-X, Tommy Gate