Any way to turn AC off when in defrost mode?

[claydoctor]

I've got 130K on my 2006 Sport and I still don't have clue how the HVAC works. It seems to have a mind of its own. It's one of the few things that I dislike about the vehicle. I'd give anything to have the option of those three simple knobs.

 

[RPC]

OrdnanceMarine- The AC's incessant cycling is the single biggest complaint about my 4Runner. For the love of all things holy, if you figure this one out please let me know.

Also, with obxfishn's mod would you need a switch to activate the AC when you desire it on? I got the impression that the mod simply precludes the AC compressor when directing air to the windshield or windshield/foot well. From the Cheap/free mods - Tacoma World Forums post: "I've tested this for a few days and the A/C will still turn on with the manual A/C button on the environmental control panel." Sounds like exactly what you're trying to accomplish...

 

[OrdnanceMarine]

I've got 130K on my 2006 Sport and I still don't have clue how the HVAC works. It seems to have a mind of its own. It's one of the few things that I dislike about the vehicle. I'd give anything to have the option of those three simple knobs.

I'm kind of getting an idea about how it works after hours of reading through various threads here. Unfortunately I'm not big on the auto function. The idea is great but the implementation just comes up short.

Funny how some people view the three knobs as archaic but I find them perfect. I want a separate button that turns the compressor on and off that does what you tell it. The rest of the system I can live with though I wish I could modify the incoming air temp even with the fan off. My "cheap" Civic and CR-V work exactly the way I want.

 

[OrdnanceMarine]

OrdnanceMarine- The AC's incessant cycling is the single biggest complaint about my 4Runner. For the love of all things holy, if you figure this one out please let me know.

Also, with obxfishn's mod would you need a switch to activate the AC when you desire it on? I got the impression that the mod simply precludes the AC compressor when directing air to the windshield or windshield/foot well. From the Cheap/free mods - Tacoma World Forums post: "I've tested this for a few days and the A/C will still turn on with the manual A/C button on the environmental control panel." Sounds like exactly what you're trying to accomplish...

I'm going to try and do what obxfishn mentioned. I may have to splice a few feet of wire into the circuit that actually goes to the compressor clutch itself in order to gain true control of the compressor (I'm not sure where the command to turn the compressor on in defrost mode originates but it has to be upstream of the compressor clutch as the command to cycle is based on a few other inputs). My vision is that once I find the right wire to clip, a simple rocker switch would allow me to leave the switch closed except for when I don't want the compressor running. I'll know more once I have time to print out the wiring schematic from the electronic service manual. If it's it's possible I'll put together a DIY with help from anyone else that has experience to add.

 

[Maritimer]

Funny how some people view the three knobs as archaic but I find them perfect.

Some things are better simple. I haven't seen much improvement on spoon design in the past few hundreds of years, either, except for the spork.

 

[OrdnanceMarine]

Some things are better simple. I haven't seen much improvement on spoon design in the past few hundreds of years, either, except for the spork.

It doesn't get much better than the MRE spork!

 

[RPC]

OrdnanceMarine, any luck?

 

[OrdnanceMarine]

Hasn't made it high enough on the priority list (been super busy) but it's 8:15 and all of the kids are in bed so if I get a few things done I should be able to sit down and start to figure this thing out.

-Dave

 

[OrdnanceMarine]

From page AC-84

DESCRIPTION
The A/C amplifier outputs the magnetic clutch ON signal from AC1 terminal to the ECM. When the ECM
receives this signal, it sends a signal from ACT terminal and the A/C amplifier switches the A/C magnetic
clutch relay ON. This turns the A/C magnetic clutch on.

I think it's time to figure out where these different lines run. Initially I think I want to kill the signal as close to the source as possible. Now I've got to dig into turning theory into reality and find some wires!

 

[OrdnanceMarine]

After about 45 minutes of figuring out how to pull panels I finally found where the Air Conditioning Amplifier lives. It's basically behind the little storage compartment right above the cup holders but below the climate control cluster. It's midnight so I'll have to pick back up on it tomorrow (hopefully) and figure out which wire I'm looking for. Good news is that if putting a switch on that line gives me the ability to override the compressor clutch engagement command (only in the "off" direction) its only inches away from the climate control cluster so wires will be short and there won't be any need to penetrate the firewall and go down to the compressor itself.

By the way, I think I found where the dealership might have lied to the previous owner. I have the dealership receipt showing that the cabin filter was changed on 6/24/2010 at 30k miles. I went ahead and pulled it while I had the glove box out and it was covered in tree debris, dust, etc. and there were numerous large holes in the filter material where the pleats had disentigrated. I've never seen a filter come out like that and I just changed the ones in my previous '05 CR-V for the first time at 51k miles and 5.5 years. Those were dirty but NOTHING like this. I suspect the dealership never changed the filter. Wonder why I do my own maintenance?

Glad I bothered to check!

 

[OrdnanceMarine]

Quick update:

Found the line I was looking for from the Air Conditioning Amplifier, clipped it and used a test lead to act like a switch and it works! I'm now able to disable and enable the compressor at will! Now I need to splice a switch in and put the interior back together. Whooo hooo!

arty:

Now the question is, who's buying the beer? :cheers:

 

[OrdnanceMarine]

First round of pictures

Here's the first pic to give you an idea of where to look for the Air Conditioning Amplifier (ACA). It's the white box partially blocked by the small storage compartment above the cup holders. Removing the panels in the 4Runner seems to be pretty simple. I'll save a detailed write up for another time (PM me if you need specific help). You'll end up pulling the entire center console to get to pull the center stack to get enough room to work.

Once you get to the ACA you remove 3 bolts and it's free. Pop out the upper of the two connectors and find wire 7 (gray with a green stripe). This is the signal to engage the AC compressor clutch. You'll have to remove some electrical tape at this point. You will need to splice a switch into this wire to override the compressor.

Here's a close up of the wire, giving you a really good idea of its position. The aligator clip in the picture was so I could jumper the wire and verify I had control of the compressor before I went through the work of splicing a switch and buttoning everything back up.

Here's a wide angle view of everything broken down and with the wires spliced. I ended up using 18AWG wire and two 18-22AWG crimp splices (available at any Wal-Mart or automotive store) and then rewrapped everything with electrical tape

Here's everything almost back together with the one switch knockout removed and the wires fed through the opening. You can place the switch wherever you feel like running the wires.

Here's a picture of the knockout that I modified to fit a simple rocker switch. It's not 100% flush with the knockout due to the curved nature of the knockout but shouldn't be noticable once installed.

Here I finished trimming my wire and crimping the connections leaving enough slack to allow for easy panel removal.

Final view up close.

Final view from a few feet back.

All in all it should take about 2 hours if you know how to remove the panels plus some extra time setting up your switch location depending on how clean you want it to look. It took me a lot longer because I had to figure out things for the first time and ended up pulling more panels than I needed to.

Let me know if you give this a try and if you have any questions.

 

[NCSCOTT]

As a few others have posted on my 04 I can turn the A/C on and off with the A/C switch while defrost is selected. I will check and see how the 08 reacts and post back with that info.

My guess is they changed it mid production like the way the cruise works. the 04 drops the current set speed if you fall below 40 MPH after braking or cancelling it. My 08 holds the last set speed, and you can recall it even if you have come to a stop. As along as you have not shut the vehicle off or turned off the cruise.

Just little things can be so irritating!!! :wtf:

 

[OrdnanceMarine]

NCSCOTT, I'm sure you know this but I wanted to post it for others. If you think you've turned off the AC compressor you'll want to listen and pay attention to changes in RPM, etc. that tell you whether the compressor is really not cycling. I've seen cars that will turn the AC light off when pressed but still have the compressor cycling away. You'll need to be in neutral (or at least stopped) and the engine will have to be at least partially warmed up or else it may be hard to notice. My Scangauge shows fuel flow and I can watch the compressor turn on and off using this reading alone.

By the way, my cruise control works the way your '08 works (the way it SHOULD work).

Now I'm probably ready to go after disabling the mommy feature in my folks' '08 4Runner that prevents you from making changes to the GPS while the vehicle is moving. I've heard that you need to clip a wire that feeds the GPS vehicle speed? Guess I'll read up on that one.

 

[OrdnanceMarine]

I just finished everything and updated the post with pictures of the final install. Enjoy!

 

[RPC]

Well Ordnance, nicely done. Looks like my weekend just got a little more full.

 

[NCSCOTT]

Thats a very Clean Mod.. Looks great.. Just wondering. If you turn your mod switch off and the computer ect.. is calling for the compressor, do you get a flashing A/C Light?? If I understand your post right, the wire you spliced into is the "activation" or feed to the Magnetic Clutch relay low voltage side/coil. The reason I ask is my Mag Clutch Relay went bad in my 04 a year or so ago and the Flashing A/C light is an indication. Replaced with $8 after market relay from digikey corp. (there is a good thread about flashing A/C light) It appears that the vehicle knows if the Mag Clutch does not engage when called for and flashes the A/C light as a failure indication. You might see that with your mod, but I am not 100% sure.

:bluejump:

I guess I would have assumed if I selected the A/C off it would have gone OFF... But you know what assuming does......

 

[OrdnanceMarine]

No flashing AC light so far. I'll have to get back into the schematic to verify what this line actually does. I remember it running to something else downstream, not directly to the compressor clutch relay. What you mention was a concern of mine because simply disabling one component of a system doesn't always mean the other components won't still try to do their job.