Defrost with NO air conditioning

[Blakers]

Does anyone know how to modify the heater control switch so we can have defrost without the air conditioning coming on? I'd like to be able to just turn the A/C on when I need it and not have it on every time the defrost is on.



I know there were plans and discussions on the gen 2 trucks, but I haven't seen anything on the gen 3 trucks.



Thanks,

Blake

 

[DuallyFox]

Why?

Blake,

Why would you want to do this? It has always been my experience that the AC helps tremendously removing the windshield/side window fog in war/humid environments. When not warm outside, I didn't think the AC compressor kicked on if the temp wasn't high enough.

I know that I'm no help here but I was curious to know why you wouldn't want the AC to come on. -Roy

 

[Blakers]

Because many times the A/C is not necessary to defrost or defog the window. I would like to control when and if it comes on. The A/C wastes fuel when used unnecessarily and does cause a noticeable vibration in my truck. Plus there are times when it actually delays melting ice on the windshield because the air is cooler than it would be with straight heat.

 

[DuallyFox]

Ok, looks like I learned something today.



I honestly didn't think the compressor came on when t was cold. Fortunetly I don't have the vibration and my defroster works great, even at 40 below.



I do, however, have the disparity between high and low heat in the cab. From my waist up I can be sweating while my feet are freezing. Hot air is rushing out of the vent near the pedal but it just doesn't get very warm. Even today where the temp reached a balmy 30 degrees, my feet never did get really warm.



-Roy

 

[dcscott]

Blake,

I don't know how to accomplish what you are trying to do but I do remember when most if not all mfgrs went to the scheme whereby the air conditioning comes on with the defrost. At the time I was told that they did this because they were having too many problems with folks not using their AC all winter, the compressor seals drying out, and viola no refrigerent come spring. They solved that problem by tying the AC to the defrost function. Don't know if there is any truth to that but that was the rumour at the time.

 

[Chipstien]

I would bet that the extra amount of fuel consumption is so small that it is hardly noticable. If this were the case then I would see my MPG down during the summer... ... not the case though.

 

[Blakers]

For reference see:



http://dodgeram.org/tech/repair/HVAC/Defrost_AC.htm



and



http://turbodieselregister.com/forums/showthread.php?s=&threadid=30252&highlight=defrost



It's been well documented on the earlier trucks, but no one has talked about it on the 03 - 04s yet.

 

[StephenThomas]

Dually Fox....

Did you say 40 below?! You should change your name to popsicle! I got cold just reading your post. I doubt any vehicle will be too warm at the lower level with temperatures that cold. Try battery operated heated socks! Geezuz... . I know if I lived there, I'd have an entire wardrobe of battery heated clothes

 

[DuallyFox]

Off topic...sorry. More on the cold.

Yeah I know. Single digits and low teens are more the norm in Anchorage this time of year but when I was up in Fairbanks a few weeks ago that's how cold it was. I used to live there and believe it or not -- I miss it. BTW, other than my feet being cold (down here in Anchorage that is) I don't have a single complaint about my Ram. It starts without a problem (I hardly ever plug it in) and even though it's a dually, it handles snow and ice better than any vehicle I've ever owned. We've had close to 6' of snow so I speak from experience. I'm glad I didn't listen to those who say duallies are worthless in the snow. BTW, I live high up the hillside so every day is a trek up and down a mountain. -Roy

 

[ddutil]

Off topic me too..

Roy, we've had 6 ft of snow too, plus lots of rain. A bit warmer here than Anchorage still.



One short question: what winter tire do you use? I had to buy four Bridgestone Winter Dueller. The traction is very fine, on ice, snow or dry pavement but they are SUV tires, not Light Truck i. e. rated 2600# instead of 3200#. The sidewalls have the ''fat'' look, even at max PSI (35).



Using the HVAC shows on my mileage, i do get the best results in late spring and early autumn on summer tires and HVAC off.



Thanks! Dan

 

[DuallyFox]

Dan,

I have the dually so the only tire available is the stock tire which is a Goodyear (Wrangler GS-A LT235/80R17E). Doing a search will reveal a lot of negative chatter on these tires but they work great for me. A little snow, a lot of snow, ice, no ice, highway, et. al. I find them to be excellent tires. -Roy

 

[Blakers]

Any aswers yet?

Has anyone come up with an answer to this one yet? How to modifiy the Defrost setting so the A/C does not come on with defrost unless the A/C button is activated?

 

[dhill]

I run the A/C all the time in the winter on my '97, heater and A/C, for me it helps keep the windows fog free and dries the air out a bit. If I can't do that with my new '05, I'm not going to be a happy camper.



Might be different with the newer trucks, but on the '97 I ran over 200 miles in 4x4 in the snow with no noticable difference in milage. Spring and fall are the only times I don't use the A/C much and I don't see any change in milage.



On my truck there is a big difference with the A/C and the defroster verses no A/C and defroster. I went through several months when the A/C compressor was broken





Dave

 

[p-Bar]

Just tie in a toggle switch where the wires go up to the compressor clutch. Then you can shut of the compressor when you are in defrost mode.

 

[Jumbo Jet]

On the older vehicles, I used to unplug the power to the A/C clutch in the winter time.

 

[bighammer]

I pull the A/C relay in the power distribution box under the hood.

 

[jsimpson]

You're better off NOT modifying. A few years back, when AC was NOT used on defrost, one of the chief causes of AC failure up north was dried out seals due to non-use of AC compressor.

 

[DFrank]

I'm confused. I never realized the ac came on with the defroster automatically. I thought you had to press the little snowflake button to activate the compressor. I would like to be able to run the defroster w/o ac for ice melt sometimes, although

i usually run the compressor for its drying features.

 

[1Tufdsl]

I'm confused. I never realized the ac came on with the defroster automatically. I thought you had to press the little snowflake button to activate the compressor. I would like to be able to run the defroster w/o ac for ice melt sometimes, although

i usually run the compressor for its drying features.

I'm confused as well. I don't think my compressor comes on when I use the defroster.



Karl

 

[Crunch]

I'm confused. I never realized the ac came on with the defroster automatically. I thought you had to press the little snowflake button to activate the compressor. I would like to be able to run the defroster w/o ac for ice melt sometimes, although i usually run the compressor for its drying features.

I think people are mixing terms here. The AC compressor comes on with the defrost, but the AC doesn't. It's functioning more like a heat pump, which may be a more accurate description of the "climate control mechanism" on our trucks. Running the compressor when using defrost dries the air and clears your windshield faster. Because it also functions as a heat pump you get warmer air faster directed up to your windshield. I'm getting luke warm air from my defroster long before my temp guage budges.