Recirculation Mode On/Off

[Friggin Idiot]

There's plenty of complaints across the different generations about Toyota changing their mind one way or another about whether recirc should be on with this mode or that mode by default.

I've learned over the years to loathe any system which requires the recirc to be off when switch to defrost mode. Yes it introduces cooler air (which hold less moisture), but when it's raining/snowing/sleeting outside, the air is more saturated outside than inside the truck. So running defrost will gradually make the problem worse by introducing more moisture into the cabin. Yes the A/C is running with defrost mode, but I still end up having to run defrost constantly instead of intermittently. This is really horrible when you need the defroster and happen to be driving by the sewage treatment plant or garbage dump.... just a wonderful smell with all that moisture coming into the cabin, thanks a bunch Toyota.

I'm hoping someone ( maybe [MENTION=83083]rigtec[/MENTION] ) might know how to wire an override for the defrost so that I could select recirc on in any mode? I thought about just closing the diverter and disconnecting power to that servo, but given the trouble I've had with mold/mildew smell from the A/C I need to leave it open to the outside some times.

 

[rigtec]

I've learned over the years to loathe any system which requires the recirc to be off when switch to defrost mode. Yes it introduces cooler air (which hold less moisture), but when it's raining/snowing/sleeting outside, the air is more saturated outside than inside the truck. So running defrost will gradually make the problem worse by introducing more moisture into the cabin. Yes the A/C is running with defrost mode, but I still end up having to run defrost constantly instead of intermittently. This is really horrible when you need the defroster and happen to be driving by the sewage treatment plant or garbage dump.... just a wonderful smell with all that moisture coming into the cabin, thanks a bunch Toyota..."

Hey there Luke!

I don't know if the Trail 'Premium' H.V.A.C. System is exactly like the 'Limited' Fully Automated-Temp Control System, but if so, you've got yourself a pretty well thought out piece of technology right at your fingertips already! Now I work in the commercial h.v.a.c., building automation field for the last 30 yrs. And in that time, I've seen some GIANT STEPS taken to change the way things operate; much like the cell phone industry has changed over the last 15 yrs!

Your automated temperature control system doesn't just warm the truck up and cool it down by hitting a button like it did in your 74 and 80's model Buick. There's quite-0-bit of sensing, calculating, and consideration being done in the short time that it takes for you to feel that air temperature/velocity change once you turn the knob! You can hit the Recirc button whenever you want (to prevent a toxic air concentration from being introduced into the cabin), but in so doing, you'll be over-riding the I.A.Q (indoor air quality) function which doesn't only look at temperature, but the proper ratio of humidification/de-humidification as well.

"...I'm hoping someone ( maybe [MENTION=83083]rigtec[/MENTION] ) might know how to wire an override for the defrost so that I could select recirc on in any mode? I thought about just closing the diverter and disconnecting power to that servo, but given the trouble I've had with mold/mildew smell from the A/C I need to leave it open to the outside some times.

Remember: that when this system needs to open an O.A.D (outdoor air damper) because the system wants to warm-up the windshield some to defrost it and the O.A. is just at the right temperature to do so, but, the humidity is high... the system will first turn on the A/C; to bring the evaporator coil temperature down to about 34 deg.F; this will remove the water that's in the O.A. Then it will open up the hot water valve to warm-up the heating coils; it'll also bring on the P.T.C. heaters to temper (reheat) the air as needed. After this it'll adjust the (M.A.D.) Mixed air damper; it does this to assure that the air temp down stream is at the right temperature to keep it comfortable in the cabin... don't forget that it's still running the air conditioning (34 deg evap) to 'De-Humidify' the warm (wet) fresh air that's being brought in to defog the windshield!

I'm giving you this hypothetical scenario just to illustrate how highly calculative our automatic temperature controlled H.V.A.C. Systems really are; nothing that you (or I) can do to 'Trick/over-ride' the algorithmic thinking of this thoroughly calculating, highly sophisticated environmental control system! I think that Toyota's Auto temp hvac system is one of the most advanced systems on the market today... kinda makes up for the blundering ENTUNE navi system that they through there in our dash lol! Hope this helps Luke,

rig, 'Best'!

 

[(none)]

Every car I've ever had automatically turns off the recirculation function once the front defroster has been selected. This is for the same reason the air conditioner is turned on at the same time, to help keep the windows from fogging and to help lower the humidity inside.

From what Rigtec states, I know in the manual it states on the non-automatic climate control models at least, the recirc is automatically selected when the outside temp is above 70 or 73F? Not sure if our models have any type of air quality monitor or humidity monitor? Anyone know for sure?

 

[Friggin Idiot]

[MENTION=83083]rigtec[/MENTION] Thank you for that detailed reply. I think the only difference between the Limited and the Base/Premium climate system is the dual zone function of climate control. I didn't realize that even the single zone was so complicated; there's a computer to run everything now! Sounds like I'm pretty much stuck unless I want to physically block the outside air intake, which is probably a bad idea.

 

[aja]

It's annoying to have to turn off the recirc every time I turn on the defrost or the AC is put on max, but it could be worse like my wife's Audi which also turns the fan up to high whenever the defrost is turned on!

 

[rigtec]

[MENTION=83083]rigtec[/MENTION] Thank you for that detailed reply. I think the only difference between the Limited and the Base/Premium climate system is the dual zone function of climate control.

You're probably right about the dual zone being the only difference; why redesign the entire system if what you have really works(?)!

I didn't realize that even the single zone was so complicated; there's a computer to run everything now!

Just the fact that most everything in our vehicle is software driven is the reason that I usually go after a software reset before I'll opt to go after a new switch or a new relay! To explain... One of our members will be struggling with which way to go when one of his/her systems in a new 4Runner malfunctions e.g., the interior courtesy lights stopped working, or the headlight system isn't working as it should, the power locks on one or more doors will lock but requires an engine restart before it will un-lock...


My thought process is that, this is a brand new truck, all of the relays and switches are brand new (Hmmm...) there's not been enough time for the contacts to wear out (all things being equal), so I might advise a software reset 'BEFORE' I'll recommend removing the door panels and inspect the mechanical linkages! There may be (never counted them) 25 or thirty ECU's that control the various systems within your truck's interrior, that get command from the 'Main body ECU Compu network'! And there is quite a bit of communication going on between these (Slave) ECU's and the MB-ECU via the CANbus system. So when something goes wrong I'm inclined to look at the system with the 'GREATEST' potential for error first!

Sounds like I'm pretty much stuck unless I want to physically block the outside air intake, which is probably a bad idea.

I was thinking about that... when the office workers in one of the facilities who's hvac systems I take care of are complaining of a strong odor, and they're all saying the very same thing, I'll ask them what does it smell like. And let's say that they describe it as "a strong scent kinda oily or karosene (and then they add...) but it seems to be a lot stronger in the morning but it goes away!" I'll know that it's coming from outside through the O.A.D.; which is usually opened in the morning (for FREE cooling) and then as the outdoor temperature rises in the afternoon, the dampers close, as their mechanical cooling (compressors, refrigerant) begin to start-up to meet the demand!

So, now that I know that the odor is coming from outside, I'll take a walk up on the roof where the A/C equipment is located, and attempt to locate source. Then I'll see on the roof of the building next door that they're having their roof replaced! That's the source! Now to eradicate the smell. I found that some air filters are a composite and are impregnated with an odor absorbing carbon base; see below:

Odor absorbing carbon filters

I know you can do a search and find a filter much like the one's in the link, that will fit directly in our glovebox compartment filter slot! These filters are highly effective in reducing/eradicating the foul odors of sewer gas, decaying garbage, rotten egg like smelling catalytic converter discharges... I've gotten them from several of the sites that I frequent e.g., amazon, ebay, walmart...etc; you just need the size, Hope this helps!

rig, 'Best'

 

[Friggin Idiot]

There may be (never counted them) 25 or thirty ECU's that control the various systems within your truck's interrior, that get command from the 'Main body ECU Compu network'! And there is quite a bit of communication going on between these (Slave) ECU's and the MB-ECU via the CANbus system. So when something goes wrong I'm inclined to look at the system with the 'GREATEST' potential for error first!

Why do I suddenly feel like my truck is vulnerable to a Cylon virus attack?

I was thinking about that... when the office workers in one of the facilities who's hvac systems I take care of are complaining of a strong odor, and they're all saying the very same thing, I'll ask them what does it smell like. And let's say that they describe it as "a strong scent kinda oily or karosene (and then they add...) but it seems to be a lot stronger in the morning but it goes away!" I'll know that it's coming from outside through the O.A.D.; which is usually opened in the morning (for FREE cooling) and then as the outdoor temperature rises in the afternoon, the dampers close, as their mechanical cooling (compressors, refrigerant) begin to start-up to meet the demand!

So, now that I know that the odor is coming from outside, I'll take a walk up on the roof where the A/C equipment is located, and attempt to locate source. Then I'll see on the roof of the building next door that they're having their roof replaced! That's the source! Now to eradicate the smell. I found that some air filters are a composite and are impregnated with an odor absorbing carbon base; see below:
Odor absorbing carbon filters

Thanks again for the help. Sadly I cannot remove the sewage treatment plant or garbage dump from their location, and an alternate route is not feasible as it adds 12-20 minutes to my commute. Sometime after the new year I am able to move, and will likely move away from where those are on my normal route to work.
I have tried the carbon impregnated filters from some of the auto manufacturers, however, the smell still enters the cabin if the vent is open. I've had to start to remember to turn off the defrost when I get on the road a mile away, and turn it back on only after I'm at least an exit past the unpleasantness. I was more concerned with the moisture issue than anything else.
Thanks again for the explanation it helped paint a better picture of what's really going on when I turn the knobs.

 

[rigtec]

"...I have tried the carbon impregnated filters from some of the auto manufacturers, however, the smell still enters the cabin if the vent is open. I've had to start to remember to turn off the defrost when I get on the road a mile away, and turn it back on only after I'm at least an exit past the unpleasantness. I was more concerned with the moisture issue than anything else..."

If you're cruising through an 'EXTREMELY' toxic environment where your health becomes an issue, there are many manufacturing companies that specialize in filtration systems that will remove down to only a few 'PPM' of whatever toxins are compromising the air quality; I'm sharing this not just for you; who may not be that concerned with simple odors that you may be coming in contact with for short durations on your commute. But there may be some members here who might have more serious concerns for their families health, and so for them, there are specialized filters designed to remove contaminants down to only a few PPM, which can make their exposure much safer!

https://www.airfilterusa.com/commercial-industrial

They're built to any custom size or application, and designed to remove a predetermined amount of contaminants; dependent upon the substance that's being removed from the air. Granted, these will be expensive (No question about that), but there are some here, no doubt, who are already invested in some kind of healthy breathing apparatus for the home... just thought it may be worth the time to mention a superior air filter for the car(s) to be in compliance with the same standards for the home! Best to you all

rig, Cheers!

 

[Friggin Idiot]

I guess you have a stockpile of those things living in Jersey and all... :wink:

Or they could always go this route....