Disable AC in Defrost Mode

So on this topic, I figured out today that the water valve cable is broken on mine. Its been full on since I got my truck and I've only been using the flap to control temp it seems, which worked well enough that I never knew anything was broken until I took things apart.

This may explain why my AC never seemed to work as well as I thought it should in the summer. I've had that hot heater core under my dash the whole time mucking things up.

 

Along with the FSM pics @Aerindel is showing back on 2nd page, below is the what is seen on a 2004 DC Limited. As stated back on page 2 in the FSM, be cautious with the 2 claws shown with red arrows below when removing microswitch, which is necessary given the way the sw and terminals are mounted. The below end result of stowing away was simply a personal preference on my part since I don't wish to let sparky accidently out.

 

The compressor is controlled by a low pressure switch on the low side, or evaporator side.

 

I thought I had read somewhere that you want to run your AC in the winter... https://stonumautomotive.com/running-cars-air-conditioner-winter-good-bad/

 

Sure. Its not that we don't want to ever run our AC in the winter, we just want CONTROL over it.

Yes, good point, it had it reversed.

I didn't remove my switch, I just angled the plugs a little and they popped off.

 

Same with your home. Run it for the ‘exercise’ and more importantly oiling of seals.

 

Yup. I'm running my 9kw generator right now, hooked up to a space heater for a load, right now just as part of keeping it ready to go.

 

Also, oil in a refrigeration system will migrate to the warmest location. Most compressors have a crank case heater, or have you ever wondered why most residential ac contractors have a bridged contactor on one leg? It’s using one of the compressor windings as a very low wattage heater.

 

Won't get no argument from me, similar to the lighter holder bulb, there is more than one way to skin a cat. Whatever someone is comfortable with, that's the way they should roll.

 

Me too. And I just left them right next to their original location: next to the switch.

 

I discovered another benefit of this mod: it allows you to recirculate while in defrost or mix mode. (that used to automatically disable when put in defrost or mix) It's great when you're trying to melt off a layer of ice in the morning. Rather than constantly having to heat 20 degree air, it recirculates the air it's already heated -- allowing the cabin to get warmer more quickly.

I imagine of those two wires, one enables A/C, the other disables recirculate?

 

Negative....the Def Mode switch is a simple SPST(single pole single throw) switch. When we select F/DEF mode it pushes on the little tit on top of the switch closing the contacts that lets current flow from 1 of those wires thru the closed contacts to the other wire.

 

Good to know!

Thanks.

 

That heating the shield with pure heat (minus AC) is nice benefit I never even considered. Good one!

 

Minus A/C makes a difference. Recirculated air makes a HUGE difference.

 

Was loving this mod this morning -- as I woke up to freezing rain. My driveway was like a skating rink, and there was a thick layer of ice on the truck.

Started the engine, set the climate control to max heat, defrost, blower on full, and recirculated air. Left it while I spread salt and sand on the driveway. When I came back, the truck was warm and the windows were clear.

 

Sounds like North Pole conditions. Your mod makes it like St. Barts inside. Awesome work on everyone figuring this out. A worthy mod for those in brutal winter climes.

 

This feature provides dryer air for dehumidifier action like in mountain rain air etc where it is more moisture then frost. The addition of a switch to interior the AC clutch will work well. Same thing for ultimate hp in street cars. Cuting off the compressor cycles is aledged to be up to 15 hp. A simple two wire circuit and a neat flush mounted switch would interrupt the power being sent to AC magnetic clutch. It would defeat the engagement of clutch. Caution advised. AC compressors need to cut in sporadically to lubricate their seals and bearings. This may cost you a failed AC compressor if left "off" for extended periods of time.

 

Yes, we know the function of A/C in the defrosting process.
As was stated at least twice so far in this thread, this mod does not disable the A/C from coming on when in Defrost mode, it simply keeps it from coming on automatically when in defrost mode. As for a switch to control power to the A/C clutch: there already is one, it's conveniently labled "A/C" and is illuminated to let you know when the A/C is active.

This mod allows operation of the A/C to be controlled by the driver so you have the option of having A/C on or off in all climate contol modes. I've done a version of this mod in my Gen-3 4Runner and was quite pleased with the results. I've now done it in my Gen-1 Tundra and am equally pleased.

If a Gen-1 Tundra owner is unclear on how A/C functions as part of the climate control system, this mod is probably not for them.
If a Gen-1 Tundra owner finds him or her self at times wanting air blowing over the windshield, but does not need the moisture-removing affect of A/C, then this mod might be for them.

 

Mild resurrection of this thread just to say thanks.
I cleaned the MAF and TB and changed the air filter trying to figure out why my truck would occasionally surge at stop lights. It never occurred to me that the dang AC was cycling with the AC button unlit. Sneaky Toyota engineering away my free will!
This is getting 'fixed' this week. I leave all of my vehicles in foot/defrost 360 days a year. (This is the newest vehicle I've ever owned.)

 

I guess I'll give an update too.

I set mine on A/C off and recirculate back in December, and only needed to take it off recirculate twice. Didn't need the A/C at all the entire winter. Although I do turn it on for a couple minutes at every start-up to keep the system active.

 

If the indoor and outdoor temperatures are low, the indoor unit's heat exchanger starts to freeze when the heat exchanger temperature is 0°C. the automatic defrost function is automatically activated." I guess we are talking about the operation of the indoor unit on cold. When the temperature reaches 0*C (as with all household air conditioners), the temperature sensor on the indoor unit's heat exchanger activates and takes the equipment to defrost. At aircon dripping water on heat, the temperature of the internal team can't be lower than the temperature of liquid). Or, more precisely, subcooling.

 

First off, where's that "thead revival" mime?

Secondly, what???

 

Battlestar galactica

 

I didn't read all of page 2 so I might've missed something, but I thought this only happened if you both (a) were in a defrost vent position and (b) the cold setting clicked over into the 'max' position?

The heat/cold range has an extra little hump at the end of the cold area to get into the 'max' mode. For the longest time I was driving with foot/defrost blend on but I'm a maniac and rarely have my cold set all the way to MAX. Recently I had to pop my bezel off to re-attach the mic cord on my stereo and flipped the cold to MAX. Next day, I noticed condensate on the outside of my windshield while driving to work. Confused, I looked to switch A/C button OFF but it was OFF already. So I just changed the blend mode to head/feet and it went away.

I guess I should test while I'm running to grab some stuff north of town today.

PS - I always run in fresh air (non-recirc) mode.
PSS - Has anyone RTFM on this to see what it says?

 

Perhaps I am misunderstanding but the cold/hot climate control knob simply moves the underhood water valve.

From FSM....