A Q For The Techs About Defrost

[prideclaw]

I need to know if there is a way, on my '04 Sierra with the base dual zone climate control, if there is a way to NOT allow the compressor to run during defrost. Can it be done with a PCL routine change in the ECM or is there a relay that can be installed. Either way it would be great to be able to turn the compressor on or off with the compressor button like the other settings ( vent, vent/floor, ect.)

I live in the south eastern US and the compressor isn't required in the winter when the windows fog up. During Summer and mild rains, yes, but the heat itself does just fine defogging/defrosting in the winter.

I know gas is dropping ( today anyway) but everything I can do to save gas helps.

Ten-Q for the input

[mkelly]

Short of installing a manual override switch for the compressor clutch relay I dont think you can control it.

 

 

However........ I would guess that disabling the a/c compressor during winter would increase your mileage something like .00000000001 mpg.........

 

 

You would see a lot bigger gain by letting your vehicle warm up before you drive away and keeping the tires inflated to the proper level.

[prideclaw]

Thanks for the input. Got all the other tips covered by the time the $4/gal mark rolled around.

While on the subject, my wife's '03 Envoy has the digital dual zone controls. Is there a way to change the compressor shut-off on hers from 38 degrees to a higher temp during Auto climate control mode

? Can't see a reason for de-humidifying at even 50 degrees around here

[ntavano95]

This is a good question and I would like to find a way to do this also. My reasoning for this is that during the cold winter mornings here in Niagara Falls I run in to the occasion where I have to start my truck and let it idle with the heat in the defrost mode to loosen up the ice on my windshield, and as everyone knows the compressor engages when in defrost mode, wasting more fuel than necessary. Now the air during the winter is already very dry, so what do I need the compressor engaged for? To put a load on the engine and burn more fuel? I dont think so. In my previous vehicle, a 2000 Ford Explorer, I found this mod on the explorer forum for a compressor interrupt switch:

 

http://www.explorerforum.com/forums/showth...nterrupt+switch .

 

So I tried it out, it worked great and was well worth it on the Explorer. So I decided to try my own version of this on my 2003 5.3L Silverado. My method was to simply splice a switch I bought at Advanced Auto Parts between the POWER supply wire of my compressor and place the switch in the cab. I did this by first cutting the wire that supplies the power to the compressor and adding about 6 feet of wire as to be able to run it through the firewall and up to a space in my dash where I was going to place the switch. I then mounted the switch in a spot next to the passenger airbag switch and bingo complete control of the power to the compressor. Turn the climate control on defrost and the switch lights up when the compressor is engaged, when the compressor disengages the light turns off.

 

I ran into a problem though. It works for about 2 mins before it begins to not work at all. In order to get the compressor to engage again I need to reset the vehicles computer by disconnecting and reconnecting the battery. Is this normal for the compressor to not work at temperatures below 50 degrees?

 

So all in all I have done what I can to the best of my knowledge but I am at a road block as to what to do to resolve the problem. This is where I am asking for everyones knowledge/ advice as to some questions I have been asking my self to resolve this problem.

 

First, it is now 30 degrees outside, does the compressor engage when it is below 50 degrees? or not?

Second, could the computer mistake my switch (when in the off position) as a malfunction with the compressor and cause it to diengage?

Or could it be something more advanced?

 

I also was wondering: Is there a wire that can I can access on the back of the climate controll pannel that I could splice this switch in to? It would make it alot easier to do that rather then running these 2 wires through the fire wall and all the way to the compressor under my truck? I have the dual zone automatic digital climate control.