[Mudog715]

Originally posted by davecsu
Mudog, thanks for the info!

When you mentioned auto climate control, are you thinking of the ones from Sequioa? Would that be difficult to do? How about cost? That would be cool!

I originally looked into transplanting the system from the Sequoia, but found a direct transplant would be impractical for several reasons:

1. The Sequoia "Integration Panel" (center control panel) lacks provisions for some things needed on a Tundra: Passenger Airbag Keyswitch & Light, 4WD Low range button and different labeling for the Cargo Lamp button (the function on the Sequoia escapes me at the moment, I think it's "VSC off").

2. The panels on both the Tundra and Sequoia interface to the engine ECU and I can't be certain that the Sequoia panel will "talk" to a Tundra ECU properly. The function of the signals between the two systems are not clearly defined in the service manuals.

3. The panel on the Sequoia also interfaces to the instrument cluster with additional 2 lines not found on a Tundra, so there is an issue if I can fool it into functioning wihout those lines.

4. The Sequoia panel would also require all Sequoia parts for the rest of the system, which include: Temp Control Amp ($450), Blower Control ($147), Air Mix Servo ($97), Air Mode Servo, Sunload sensor, In-car sensor, Ambient sensor, and the control panel itself. New, these parts are in excess of $1,500 from a Toyota dealer (wholesale pricing, BTW, lower than the "discounted" price places like Carson charge us). That cost makes it impractical. Finding the parts at a junkyard are near impossible -- it's hard enough to find a wrecked Tundra, let alone a Sequoia! And, again there is the possibility that they may not function without a matching Sequoia gauge cluster and engine ECU!

So, the alternative I came up with was designing my own system from scratch, using a few pieces from the Sequoia system (Air Mix Servo & Blower Control) and reusing the stock Tundra Integration Panel. It would also use the outside temp sensor included with the comp/temp mirrors as the ambient sensor, add an in-car sensor & sunload sensor.

The Integration Panel would remain stock in appearance, with the three rotating dials, however the following functions would change:

1. The blower control (Off-Low-M1-M2-High) would become Off-Low-Auto1-Auto2-High). As implied, in the two "Auto" positions, the blower speed would be controlled automatically at one of 32 (!) discrete levels. The speed would ramp up and down, almost imperceptably, as needed to maintain the cabin temperature. The speed would also be increased 10% in the "Auto2" position, and increase up to 20% based on the signal from the sunload sensor. The Low position would yield a fixed speed approximately between the current Low & M1 speeds, and the High position would fix the speed at maximum.

2. The temp control (Cold---Hot) would be replaced with a potentiometer and become the set temp. dial. Markings would be Cold---65(9o'clock)--75(12o'clock)--85(3o'clock)--Hot. The temp dial position would be read by an ATC (auto temp control) computer of my own design and would set the temperature the system would maintain. At the dial extremes (full Cold or full Hot), the system would be "overridden" and drive the Air Mix Servo to either the full hot or full cold positions. Otherwise, the ATC computer would vary the Air Mix Servo to maintain the set temperature. I considered replacing this dial with 2 buttons and a digital readout, but decided against it because such an arrangement would require the user to look at the display to confirm changes -- a potention distraction while driving. Almost all the stock ATCs these days went back to a rotary knob for temp setting for this reason.

3. The "Recirc" button would operate as stock with 2 exceptions: 1. In the "fresh" position, the ATC computer would switch to "Recirc" automatically in situations when "Max A/C" is needed (various criteria would be considered, including outside temp, inside temp, and the temperature rate change). 2. In the "recirc" position, recirc would only be allowed for a maximum period of time, which would vary if the A/C was on vs. off, then it would automatically switch back to "fresh" This is the way most stock ATC's operate and they do this to prevent fogging of the inside windows in cooler, humid weather and to prevent the formation of "musty" smells in the A/C ductwork and evap. coil.

4. The A/C button would operate as stock. The ATC would vary it's operating strategy when on vs. off.

5. The Mode dial would remain manual. This is to keep the system simpler and costs down. I did some quick figuring and adding full-auto mode control to the system would add $200 to the total cost. For me, at least, I'm most interested eliminating the "fiddling" of the manual system so auto blower and temp control are my goals. Having to occasionally rotate the dial from panel to floor is no big deal. Also, some auto systems don't deal well with situations where the outside temp. is close to the desired (set) temp -- they may not pick the mode setting that the driver prefers, so the driver ends up overriding it anyway. One thing that would be automated is the "Defrost" (full clockwise position) -- in that position the ATC computer would override the "recirc" button to "fresh" and reduce the rate at which the blower speed reduces as the system approaches the set temperature (ie. keep the speed "higher, longer") to aid defrosting. It would NOT force the A/C on, as the stock Tundra system does, however if you performed the mod to disable the stock "defroster linked A/C" (as Toyota calls it) you will have to reverse the mod for the ATC to sense the "Def" mode correctly.

A couple of additional, optional functions (user enabled):

6. The A/C can cut out under WOT and the cut-out time limit could vary according to temp demand (hotter outside, less cut-out time).

7. When A/C was on and the vehicle stopped and turned off, the system would switch to "fresh" and run the blower at medium speed for a few minutes to purge condensation from the evap coil. This will help reduce the mold build-up that causes the musty smells. The time would vary automatically according the circumstances (ie. if the system was operating in Recirc prior to shut-off, then the "purge" time would be longer).

8. If the vehicle is equipped with a remote starter and the remote start was activated, the system would automatically switch on the A/C if the driver left it off but the outside temperature is 5 deg higher than the set temp.

9. Upon unlocking the vehicle with the keyless entry or alarm, and the interior temperature is more than 5 deg over the set temp, the system would enter the purge mode described in #7, except at High speed and only until a door was opened or 60 seconds passes, whichever comes first.

10. A control output would be provided to activate (user-added) heated outside mirrors based on ambient temperature and other conditions. The output would "cycle" as needed to maintain the mirrors defogged, but prevent overheating of the mirror elements. In other words, "automatic heated side mirrors."

11. A control output would be provided to activate (user-added) heated seats based on ambient temperature, as soon as either 1. the truck is unlocked or 2. remote start activated. In the case of activation with an unlock, they would shut off within 5 minutes if a door isn't opened and truck started.

12. Because the system has a sunload sensor, it would double as an ambient light sensor and outputs would be provided for full auto on/off control of the headlights.

My goal is to be able to put a kit together in the $500-600 range. Because of the cost of the individual parts, I doubt I'll be able to get it much lower. If I can't get it down to $600, then I doubt I'll make a kit because I'm guessing it would be prohibitively expensive for most people.