GenVibe - Community for Pontiac Vibe Enthusiasts

I had seen somewhere that there was an easy way to "modify" 2003-2008 Vibes to prevent the A/C from automatically engaging with the vent control set to Defog - but nothing for the 2009's - so I figured it out myself.To get at the controls, first remove the trim around the radio and HVAC controls by starting at the bottom and "unhinging" it at the top. You'll then need to unplug the connectors going to the hazard switch and passenger airbag warning lights. There are tabs securing the HVAC controls at each end which only require slight depression to allow the controls to detach and move towards you. Don't pull them too far - they're attached by cables you don't want to break. Behind the mode control knob (left), there's an electrical connector with 8 wires coming out of it. The one you are looking for is the yellow one. I pushed the black outer protective sheath on the harness back a bit to allow me to cut the wire about 2" from the connector, then taped over the ends and tucked the cut portion back inside the sheath. Now just reverse everything you took apart, and you're done!Now you can operate the car in Defog mode without necessarily running the A/C - but you still have the option of selecting it with the A/C button at any time. Today was a very wet and cool crappy day (8C), and my windows cleared just fine without having to use the A/C. I found that it allowed the air to get much hotter more quickly (no A/C cooling it first) as well. I just like being able to keep some heat on the glass without using the extra gas to run the A/C. Most of my previous cars never came with A/C, and I never had an issue keeping the windows clear. At least this way I have the option if I still feel it's necessary.I'm sure that there's a way to de-pin the yellow wire on the connector as well - but I didn't see an obvious way for this particular one. I would have preferred to do it that way - but I figured cutting the wire in the middle of the span gives me ample room to re-connect it if ever desired. I'm just very happy that it worked as I intended! Other than my trailer hitch/wiring, this is my Vibe's first "mod".I hope this is of use to someone else. Just today I had three other people ask me if I could figure out how to do the same to their cars too. Unless it's another Vibe/Matrix, I'm not going to get into any more "fun". I have the factory service manual for the '09 - which was of help for the schematic.John

Why stop the A/C on defog?The A/C causes dried air to dry off the inside of the windscreen.

because sometimes you want heat on the windshield and not cold air. By doing this mod you can control if the ac compressor under the hood is engaged and running.

Ok, I see your point.But...If you want warm air to the windscreen just move the temp dial to hot.If you want to save the MPG of not running the A/C compressor defog is not on very long anyway ... 5 minutes?

With the damp weather around here, and the wet highways in the winter - often I need to keep heat on the windshield for my entire commute - which is about 58km each way. Yesterday the traffic wasn't moving very swiftly with the rain and poor visibility - so it saved me from having it running for about 1.25 hours.I also tow on occasion with the car, and figure everything has enough work to do - so if I need to clear the windows I don't have to add the load of the A/C as well this way.I just prefer to be able to CHOOSE whether or not the A/C is engaged at any time. I have a couple of friends that actually pull the fuse for the compressor in their cars at this time of year to disable it - but to me that wasn't an ideal solution. I think it's still a good idea to exercise the system for at least a few minutes every couple of weeks to help keep the seals lubricated.I've also often experienced having the windshield completely fog over when starting the car - if the A/C was used on the previous trip. The water in the evaporator quickly transfers itself to the glass - but it then takes a good couple of minutes to get the air warm enough to get rid of it. I can now eliminate that problem.Personally I just don't like much of anything being done "automatically" for me. My transmission is still driving me nuts on a daily basis (auto), but the amount of stop/go traffic I encounter on my daily commute - plus the fact my wife doesn't drive manual, meant having a clutch again just wasn't practical. We'll see how long I go along with the automatic headlights before maybe wanting to do something there too.I really should mention that I'm a bit of a "fuel economy junkie" - so having that compressor run anytime I don't feel it's absolutely necessary just bugs me. I'm much happier with it now.Now if I could just re-program that transmission so that it wouldn't be so willing to unlock the torque converter with the slightest throttle movement. It seems to me that it was programmed almost entirely for performance and smoothness - with little concern for fuel economy. But that's an entirely different rant...John

Quote, originally posted by j42.snyder »...I just prefer to be able to CHOOSE whether or not the A/C is engaged at any time.......I really should mention that I'm a bit of a "fuel economy junkie" - so having that compressor run anytime I don't feel it's absolutely necessary just bugs me. I'm much happier with it now....OK, I'll give you that.

With out tearing the dash apart, I think that I would pull the wire out of the AC compressor plug and run a neat jumper wire along the inner fender and then inside the body. You can purchase small corrugated wire harness. I'd cover the wire and zip tie it to an existing wire or pipe. There would be two wires, one returning and plugging into the AC Compressor. I'd then put a switch somewhere on the dash. Ideally it would be below the AC switch already there but that is just a dummy and no real switch is available. A clever person would probably be able to insert a small rocker switch that would blend right into the fake button. I've had mine out, it's just a plastic dummy button.I'm also sure there is a wire in the dash harness somewhere that activates the compressor, bypassing the dash switch when the Defrost is on. I don't have a wiring diagram yet for the car and besides, I HATE to cut into factory wire harnesses when there is a less invasive manner to accomplish a given wiring task.Dave

With the mod ya done,does the ecm still put the motor in a higher RPM level with the defroster on? I really don't like the compressor being engaged either,but havent had the time to figure out a way to do it,I was just thinken of disconecting the line pressure switch since its right there on top, instead of yanking it off the compressor itself. I think i used the AC twice so far,but I use the defrost more.

Like I said previously - this modification allows full NORMAL operation of the A/C EXCEPT that it doesn't "force" it to run when the mode switch is set to Defog. Everything operates the same, except that the car now doesn't "know" that you've directed the air to the defog vents.I'll attach a scan of the schematic. On the schematic you'll see that the yellow wire coming from Pin 1 of the Mode switch is wired in parallel with pin 3 of the temperature switch - which is where the A/C control button is located. By disconnecting Pin1 of the Mode switch, it affects no other operations. You can still choose to run the A/C while on defog if desired, but it's no longer "automatically" engaged.I tried to de-pin the wire from the connector - but I wasn't familiar with that particular one, and couldn't see how to do it properly. That's why I cut into the harness at a safe enough distance that I could easily splice it back together if desired. I was more concerned about that because I hadn't seen it actually work yet.One thing I omitted - I forgot that I had to also remove the bezel around the shifter to allow the HVAC controls to come out. I realized that when doing the same mod to my brother's Vibe today. If it's an automatic, place it in Drive, and unscrew the shift knob. Start lifting the bezel off at the bottom, and once it's free, unhook the wire going to the shift indicator light, and it will lift right off. I think it took me all of 5 minutes on my brother's - mainly because I took my time. Gotta love these "snap together" cars...Although I did cut a wire in the factory harness - to me it was still less intrusive than adding more wiring through a hole somewhere in the firewall, and mounting another switch somewhere. This offers FULL manual control of the A/C, with no obvious drawbacks that I can see. The cut wire is inside the car - so even if you desire to reconnect at a later date, corrosion shouldn't be an issue.Pulling a wire off somewhere else to completely disable the system probably isn't advisable. It really should be exercised at least occasionally to keep the seals lubricated. About 10 minutes every 3-4 weeks is probably all that's needed. I paid plenty to get the A/C - so I want it to keep working - but only WHEN I want it to.Hope this helps clear things up a bit.John

Attached files

I'm curious about when the A/C automatically comes on and how you know it is on. Does the A/C come on automatically when turning the mode dial to "window" or "floor & window"? Does the A/C light turn on? When I tried this in my car, the A/C light did not turn on. Does that mean my A/C is not on? Or it is on, but with no indication?

There is no indication. It only works on Defrost or Floor/Defrost setting.The obvious way of knowing from inside the car is that any internal fog on the glass evaporates almost immediately.Without the AC it will take awhile for the warm air to evaporate the moisture.If you know where to look you can pop the hood and see that the AC clutch is engaged if you need to visually verify its operation or non operation.Dave

Guess I need to do this mod then... I generally leave the mode switch in the floor/window setting all winter!

I wondered if the AC was coming on when I was using defrost. In our Hondas it comes on and the indicator light comes on. In the Vibe, I'd feel cold air but no indicator light so I wasn't sure.

Quote, originally posted by djkeev »If you know where to look you can pop the hood and see that the AC clutch is engaged if you need to visually verify its operation or non operation.DaveNo external clutch on the compresser,I already checked that out.From what I can figure,it's internal.http://forums.genvibe.com/zerothread?id=39090

The only time the defroster will blow cold air is if you have the temperature dial turned to cold. If you want warm air, turn it to hot. One reason for having the A/C pump on when the defroster is on, is to keep it from freezing up during the winter months.

My A/C doesn't activate when turned to defog... Is it suppose to? :S

Quote, originally posted by 09vGT »My A/C doesn't activate when turned to defog... Is it suppose to? :SThe light on the dash doesn't come on, but the A/C pump should be on. Many people won't notice this.

I can feel mine kick in with the control on hot & the dial turned to defrost mode,I also notice the RPM's increase.Unfortunatly i have too many other things goen on now to further investigate.

That's a handy feature to have. The Hyundai I have now just needs a secret sequence of pushing buttons to disable the forced A/C, I'm pretty fortunate. lol! I use the A/C long enough to get rid of the fogging, then it's usually ok to leave it off. Any reduction in the compressor running is good for fuel economy. It's still a wise idea to use the A/C with some frequency during the off season, the compressor needs to run every so often to keep the seals/etc lubricated. Unless the outside temp is below the threshold of compressor operation, then I guess it doesn't matter either way since it isn't going to engage.

Not everyone realizes it but according to my '09 owner's manual the AC operates when the controls are in the defog or the defrost mode. Those are the two positions all the way to the right.I like your mod, thanks for the advice. I have only had my Vibe for a few weeks but have noticed that I have to apply air flow to the windshield more often than my old Mercury to prevent fogging. I don't feel it is necessary to always have the AC on during defogging. Last night I drove approximately 100 miles. When I went out this morning I discovered that I did the entire 100 miles with the defog mode on. Unnecessary and I'm sure it cost me a little gas mileage.If I understand your post correctly; you can now still use the AC during defogging by pushing the AC button manually when in the defog or defrost mode. Is that correct?

Yep, just toggle the A/C button when you need dehumidified air when in defrost or floor/defrost. Once it's satisfactory, then you can hit the A/C button again to turn it off.

Quote, originally posted by ColonelPanic »It's still a wise idea to use the A/C with some frequency during the off season, the compressor needs to run every so often to keep the seals/etc lubricated. Unless the outside temp is below the threshold of compressor operation, then I guess it doesn't matter either way since it isn't going to engage. This is one reason the A/C pump runs when you are on the defrost/defog mode.Quote, originally posted by beemerphile1 »Not everyone realizes it but according to my '09 owner's manual the AC operates when the controls are in the defog or the defrost mode. Those are the two positions all the way to the right.I like your mod, thanks for the advice. I have only had my Vibe for a few weeks but have noticed that I have to apply air flow to the windshield more often than my old Mercury to prevent fogging. I don't feel it is necessary to always have the AC on during defogging. Last night I drove approximately 100 miles. When I went out this morning I discovered that I did the entire 100 miles with the defog mode on. Unnecessary and I'm sure it cost me a little gas mileage.You probably did lose some mpg's as you always will with the A/C pump running. This is a great mod if you remember to run the A/C pump to keep it working right. I leave mine the way it is just so I don't have to remember to do it.

Straight heat on the windshield that is frosted over helps to deice it faster than if the A/C was on too. I did the mod on my Civic years ago, had to push like 3 buttons in sequence, hold some down, turn the key to run, stand on my head and pray to the Honda God and it worked.There has to be a way, or just run a bypass from the A/C switch and make your own switch to work when you want it.

Quote, originally posted by Whelan »There has to be a way, or just run a bypass from the A/C switch and make your own switch to work when you want it.The point of this post is that I DID find a way - with no extra switches or wiring. Just one snip - and you still have full control with the factory A/C button. It will now work just like the Honda did.John

Does anyone know if this yellow wire snip is the same for 1st gen Vibes??? I have an 04, and read somewhere to just remove a switch by the selector? and I found this post just to cut the yellow wire... If someone has done it please let me know thank youYohei

03-08 can just hit the button on the dash to turn it off... at least that is how mine works LOL

Hey Keith, maybe you already have the mod done and you dont remember doing it Cause my car, even with the ac switch off, and the light is OFF, the AC still kicks in when the defrost or defrost and feet are selected.....

I remember doing something, vaguely. I would have to look

Good job, over the years people have torn into most everything in the 03-08 vibes, nice to see people digging in to the 09-10's. I did this mod on my 03 some years ago and have had no problems or regrets. On the 03-08's its easier, just unplug a wiring connector from the back of the hvac controls. (for link, look in the "vibeowner website moved" thread in genvibe's Links section)

Joatmon, thank you very much!!! I found the site.http://home.comcast.net/~vibeowner/buzz ... den.htmfor anyone interested in doing it. cant believe Ive been suffering with this for so long and seems very simple! thank you yohei