***Edited for a typo and to add some info here and there***

FYI: Due to a good number of stock HVAC failures on the 07 tC, I feel I should warn that if you have had ANY issue with your stock HVAC lighting or a faint burning smell it should be looked at by the dealer. There have been many lately posting on these issues on the stock board, so you dont want to go modding it if you think these issues may be present.

This is the newest incarnation of the HVAC mod for running blue, green or white LEDs.. If you are running red LEDs or are only swapping the gauge LEDS, then you do not need to perform this mod. As always, I take no responsibility for anything you may do to damage the board. The mod itself works, but you always take a small risk of damaging something when you begin modding. I have 6 years of schooling and 2 degrees in the areas of electronics engineering (telecommunications and control systems) and engineering management, for those leary of taking someone on the internets mod and applying it to your baby :P But like I said, be careful not to damage anything while working. I reccomend taking static precautions since you are working around static sensitive devices, using a soldering iron with proper ESD protection, etc.

Before beginning, it is a good idea to determine if this is a job you want to tackle if you do not have a lot of experience with this. Below is a list of what is involved:

1. De-soldering the LCD for the clock. This is probably one of the more tedious pieces. This takes some patience to do right and can result in a broken LCD, which is replaceable only through purchasing an entire HVAC module. So be careful on this step!
2. De-soldering all LEDs and some surface mount resistors. These parts are very small, so be ready to work with tweezers.
3. Soldering the new parts back in and soldering in the LCD

Tools you will need for this:

1. Soldering iron: 25-30W is plenty. Work quickly if you use a 30W iron. A temperature controlled iron is recommended, but I realize many may not want to spend $150 or so for one of these. You will need a small pointed tip for this (if using Cooper/Weller irons, I recommend an ETO or ETA tip).
2. Solder sucker: You can purchase a cheap one that is heated from Radio Shack or a similar store for around $10. Solder wick works great as well, but if you are not experience using it, the sucker may be a better option
3. Solder: You will need a small gauge solder for this.
4. Tweezers
5. Needle nose pliers: to remove the temp knob lock nut

Parts needed for the 2007 HVAC board

16 - PLCC-2 LEDS (18 if you want to do the gradient effect on the temp knob)
3 – 0805 package 43 Ohm SMT resistors
1 – 0805 package 130 Ohm SMT resistor
1 – 0805 package 420 Ohm SMT resistor
1 – 0805 package 680 Ohm SMT resistor
1 – 0806 package 560 Ohm SMT resistor
1 – SP-3SU package +10V regulator 1.2A rating


Ok, let’s get started.

I don’t recommend this if you are not familiar with or comfortable with soldering and wiring. I won’t go through soldering techniques or disassembling the console, as this has already been covered in these other posts.

http://www.scionlife.com/forums/viewtopic....t=37747&start=0 (http://www.scionlife.com/forums/viewtopic.php?t=37747&start=0)

http://www.scionlife.com/forums/viewtopic....t=61793&start=0 (http://www.scionlife.com/forums/viewtopic.php?t=61793&start=0)

I will focus on the circuit design. I will note one thing though. Be VERY patient with the LCD. Use solder wick and/or a desoldering iron, and move from one end to the other so you are not focusing heat on one area too long. It will seem they will never come loose, but there is solder all the way through, so it takes a while to get it all out. Don’t try removing it until you can see all pins on the bottom move when you wiggle the display.

1. On the front of the board, de-solder the following parts:
a. R302 – Top left side of board, marked in red in Figure 1 below
b. R301 – Left of leds under clock LCD.
c. R305 – upper left of TEMP knob LEDs. Marked in red in Fig 2
d. R306 – lower left of temp knob. Figure 2
e. R307 – lower right of temp knob. Figure 2
f. All LEDs you will be swapping

2. On the back of the board, de-solder the following:
a. R304 – Marked in red in figure 3 below. Top left
b. R303 – Middle-right side. Fig 4 Below
c. IC300 – Middle Right. Figure 4

3. Replace the removed components with the new values listed below:
a. All LEDS removed previously
b. R302: 0805 package 43 Ohm SMT resistor
c. R304: 0805 package 43 Ohm SMT resistor
d. R303: 0805 package 43 Ohm SMT resistor
e. R301 (Clock): 0805package 130 Ohm SMT resistor
f. R305: 0805 package 420 Ohm SMT resistor
g. R306: 0805 package 560 Ohm SMT resistor
h. R307: 0805 package 680 Ohm SMT resistor
i. IC300: SP-3SU package +10V regulator 1.2A rating

4. This is a good time to plug the unit back in and test. Make sure to push all of the buttons and test all functions now so you don’t end up taking it back apart later.

5. Solder the LCD back into place. Be careful to move end to end while soldering so as not to overheat one area.

6. Clean all connections with rubbing alcohol and dry thoroughly

7. Plug in to test once again

8. Re-assemble HVAC module, install and enjoy!



Figure 1
http://i4.photobucket.com/albums/y111/engifineer/2007_HVAC3_Left.jpg

Figure 2
http://i4.photobucket.com/albums/y111/engifineer/2007_HVAC3_temp.jpg

Figure 3
http://i4.photobucket.com/albums/y111/engifineer/2007_HVAC3_Right.jpg

Figure 4
http://i4.photobucket.com/albums/y111/engifineer/2007_HVAC3_LeftLower.jpg

**EDIT** Thanks to Garage1217 for the correct designator for the resistor under the LCD!

Very nice, but i wouldnt recomend any amature to preform this procedure. I had Karl from Little ferry NJ do my friends gauges and HVAC and he did hundreds of scions. The LCD clock is the worst part, Karl used a Solder sucker and alot of patience.
IDk if Karl replaced that many resistors but he did a rerouting thing for more voltage. The information you gave with the resistors might be very helpfull.
Still i wouldnt go through this much trouble to do it myself, i rather pay $100 to get it done perfect then worry about breaking parts and buying equipment. I giver you a lot of probs for taking the time to share everything thou

I agree that it can be tedious. But I am the one that designed the circuit mod he used on yours.. so I am prepared to do it :P I I have done a few myself :D This is my newest mod, which makes it much easier.

http://i4.photobucket.com/albums/y111/engifineer/2007_HVAC3_LeftLower.jpg

The upside down 431 in this pic kinda looks like it says lED.... :eyebrow:

Do you know where to get HVAC replacements in case we screw up? :D

Dealers? I think they'll just rip us off.

subscribing for future reference.

subscribing for future reference.
unnecessary
just added to TECH section

thanks quiet.

For any parts like this, go to car-part.com. It links to tons of salvages all over the US. You can usually get them for $75 - $100 in good shape.

thanks quiet.

For any parts like this, go to car-part.com. It links to tons of salvages all over the US. You can usually get them for $75 - $100 in good shape.

no problem

where can i order the SMT resistors? is there an online site i could order them all through?
thanks

EDIT
and where can i get one of those regulators?

digi-key or mouser can provide you parts online.

:)

digikey is my preferred vendor for all of the parts.

311-43ARCT-ND RES 43 OHM 1/8W 5% 0805
311-680ARCT-ND RES 680 OHM 1/8W 5% 0805
311-560ARCT-ND RES 560 OHM 1/8W 5% 0805
311-422CCT-ND RES 422 OHM 1/8W 1% 0805
311-422CCT-ND RES 422 OHM 1/8W 1% 0805
311-130ACT-ND RES 130 OHM 1/8W 5% 0805
AN7710SP VOLT REG POS 10V 1.2A SMD SP3SU

:)

I will also be buying in bulk, so you can probably get them through me easilly as well.

:D

well... if i were to use or find 0805.. yes.. but i'm glad my local Fry's Electronics carries 1206's and (yeah they're ok) NTE products which they probably have, but haven't checked yet, the regulator.

awesome thanks guys

You can use the 1206 on both models as well as squall said. The 1206 is slightly big for the 07 and the 0805 is slightly small for the 05/06

The regulator is a slightly different package (smaller) than a standard one. But Fry's may have it.

You can use the 1206 on both models as well as squall said. The 1206 is slightly big for the 07 and the 0805 is slightly small for the 05/06

The regulator is a slightly different package (smaller) than a standard one. But Fry's may have it.

just to make sure...

the same parts that are needed for the 05/06 are the same for the 07's?

also... does this look correct? [all in quantities of 10]

311-43ARCT-ND RES 43 OHM 1/8W 5% 0805 SMD
311-680ARCT-ND RES 680 OHM 1/8W 5% 0805 SMD
311-560ARCT RES 560 OHM 1/8W 5% 0805 SMD
311-422CCT-ND RES 422 OHM 1/8W 1% 0805 SMD
AN7710SP VOLT REG POS 10V 1.2A SMD SP3SU

it also says to contact Digikey about hte 130 ohm resistors... hmmm

hmmm.. that's what i'm concerned about... Fry's might only have the regular size... i couldn't find a cross reference match for NTE online for Panasonic's AN7710SP... but was able for just the AN7710...

I actually used 120 on mine. The LCD is a tiny bit brighter than the odometer LCD, but I like it that way. Any 0805 130ohm resistor will work, so you can try a few different part numbers. Some of thier part numbers reflect buying in bulk. Search for 130 OHM 0805 and you should find what you need.

For the 05/06, I reccomend using the 1206, which is the correct size for it. They are a little larger. You can use the 1206 on the 07 as well, but it will extend right to the edge of the pads, so make sure you get good heat contact on the pads when soldering them. I am anal.. so I like to use the stock size :P

Here is a pic of the 0805 package resistors to give you an idea:

http://i4.photobucket.com/albums/y111/engifineer/HVAC3_0146.jpg

For the regulator squall, you will need to look up the pacakge dimensions for both to make sure they match. The one on the board is a little smaller than the average regulator ic. Whats cool about the ones I got from digikey is that the middle leg comes pre-clipped and the leads are already bent. It is a simple swap and solder.

Now, to finish up my other few mods! We are leaving in a little bit for OK (nice 9 hour drive :tap: ), so I will talk to you all later!

Very good man :) I was wondering when you would make a mod to change the reg, mad props to you! You have taken the pain and suffering out of swapping for all of us solder slingers! :)

so, let me get this straight... all those parts that you have listed will fit the 07 right? or will some of those wont? im confused. LOL!!

there's two different writeups... this is the '07's.. listing the 0805 sized...

so YES. :P

Edited it a bit to add some info here and there and fix a typo or two :P One main typo was the year models listed for this.. should have been 2007 for this writeup obviously.

bump to add a little heads up on the stock 07 HVAC issues. See bold text in the write up on page 1.

Also, if a mod sees this *hint hint :P * it may be a good idea to change the title of the link to my other write up to 05-06 HVAC LED Swap and this one to 07 HVAC LED Swap in the tech section. Right now, if someone did not notice the 07 one, they may be confused by the other title, which seems to infer it applies to all models. This was originally because I wrote it in 05, but now that there are two I think they should be changed.

Thanks
Dave

check! done! :)

Good man! I figured you were out there lurking somewhere :P

:D no problem.. did wonder why it wasn't done before... *shrugs*

So what's the word on doing this mod... I wanted to do that back in October but there wasn't a clear write up back then. Now theirs issues?

How many people have had their HVAC boards smoke/smell? Is it enough that I shouldn't attempt this?

The failures are not related to the mod. They are an issue with the 07 boards. I have heard of LOT of them already failing with nothing done to them. Honestly I would expect a recall if it keeps going like this.

The mod itself though is the same between the 07 and the rest. The difference is in the component placing and package size. I created the mod for the 05 back in 05 and have done tons of those. I updated for the 07 mod not too long after they came out. There wasnt as nice of a write up for it until later though.

The risk you run if you mod it is that if it does have issues like mentioned here, then the dealership is more likely to blame it on you for modding it. Obviously, I like the business, but I personally would reccomend waiting it out to see if they fix the issue with the stock boards before doing anything to them. That is kind of shooting myself in the foot as far as doing the mods, but I would rather reccomend what is best for the car owner rather than my wallet :) But, there is also a chance that if you have had it for a while with no issue, you wont ever have the issue and will be ok. So it really is up to you and what you are willing to risk.

Ebay has them if you mess yours up like I did :doh:
I got my replacement for $40 shipped the dealer wanted $700 for it!

Im wanting to do this mod myself. One of you guys said that you offer the kit which includes everything i need including instructions. Somebody PM me and we can arrange something.

I went to my local electronic store and also Fry's electronic but they only have either +8V 1A or +12V 1A. I bought the +12V 1A one. Would this be ok or does it have to be exactly +10V 1.2A ??

Also, I think it looks rather big

You will have to re-calc the resistor values if you use a 12V regulator. And they probably dont carry the same package design as the one needed for our board. I carry all the parts for these in bulk if you need. Either that or you can order from digikey, but then you have to pay a $5 minimum order charge for a $2 part :P

Another question, why is the ground leg cut off ? How can the voltage regulator works with the ground cut off like that ?

The heat sink is also connected to ground. That serves as the ground most times.

e. R307? (Clock): 1206 package 130 Ohm SMT resistor
h. R307: 1206 package 680 Ohm SMT resistor

engifineer, in your original post, you said to replace R307 twice. So what does that mean ? Which value should R307 be ?

Also, I pm you about buying the voltage regulator, did you not get it ?

thx

WARNING: be careful with the LCD Screen.

I had to buy the whole HVAC from a salvage yard for $75 just to get the LCD screen.

e. R307? (Clock): 1206 package 130 Ohm SMT resistor
h. R307: 1206 package 680 Ohm SMT resistor

engifineer, in your original post, you said to replace R307 twice. So what does that mean ? Which value should R307 be ?
edited for typo.

R301 should be the one for the clock and should be the one that is the 130 ohm.

Sorry about the typo! Also Vortex, I had messaged you back (or thought I did at least). I will resend.... sorry about that!

Ahh, no wonder the lcd screen looks a bit dark. No problem

As far as for the voltage regulator, I used the +12V I bought at the store and it seems to work fine. It was a lot bigger than the stock one and cover up the soldering pad for the heat sink so i had to solder a wire running from the heat sink to the solder pad, the voltage regulator now sit slightly above the board. Of course I also used slightly higher ohm resisters. But I will still buy 2 from you for future use

For a 12V regulator, you should have used approximately 4 times the resistance to prevent leds from dying early in life. So around 160 ohms for the buttons, and 500 or so for the clock. If you didnt go this high I would reccomend using one of the new regulators I am getting ready to send you. I can send you the whole thing (regulator plus resistors) for 7 bucks per, so the price is pretty insignificant.

Haha, oopss, I did not use that much resistance. You asked for 43Ohm, i used 47, for 130Ohm, i used 140 something, for 420, i used 470. Something like that. I could not find the exact value you asked for.

I will PM you

For the parts you just ordered, I will just throw in some resistors for this one when I ship... dont want you going lightless in the near future :D

So what is the exact voltage and current draw for PLCC ?? Usually I use 3.4V and 30mA whenever I need to calculate the resistor value. Most of the time, to avoid installing resistors, I just connect 4 of them in series. Is that ok ?

It is usually not a good practice to run without limiting resistors. 20mA usually the safe limit, but you wont see much difference in brightness over about 16 (most change is going downward from there). I usually calculate using 3.2V and 15mA if I want them bright. The actual forward drop will vary slightly at different current levels, but that is a pretty safe value.

where can i buy this light for my car?

pm sent!

I was thinking about doing this mod to my car, but I have an '07. My current HVAC is working just fine. But, I was wondering if anyone knows if the '08 HVAC unit will work just fine in an '07 car. If so, I was thinking of picking up an '08 board from a salvage yard and doing the mod on that and slipping it in the car instead of modding the '07 board. Does that sound reasonable?

yup.

where are you at btw?

San Jose too :)

I have a question for anyone about the LCD on the HVAC. I just did a swap to blue on all of my gauges and everything worked fine. The only problem(s) I ran into were on the LCD. I can not get the blue leds to light. I first thought I had one on wrong, but they were all correct. I redid the solder on all 3 and still no change. I re-installed the original leds and it worked. Even tried switching them one at a time and as soon as I would swap any one of them, they would all stop working. I have not done the resistor changes yet as they were not available at the time, and I may not even do them, as the buttons are bright enough for me as is. Anyone have any clue as to what may be happening?

Oh, the other problem... I managed to crack the damn LCD, ehich just topped off tonights install. Anyone have an extra?

You will need to purchase an HVAC to replace the LCD unless someone just happens to have an extra. Look for a used one (car-part.com is a great place to look).. since a new one is over 500 bucks.

The leds under the LCD may not light up at all without the resistor and regulator fix. I cant imagine the buttons being bright enough for anyone without that mod either. Before I came up with the mod, some that had tried the led swap actually swapped them back because they were so dim.

But either way, the LCD backlighting is probably going to be the worst of the bunch and may or may not light at all without the mod.

I have a 08 tc, and i'm having a hard time putting the climate control knob back together. There are a total of 3 pieces and i don't know which came first.

The clear portion slides onto the potentiometer. The metallic parts snaps over it. If you look around the edge of the knob face you will see 3 holes. Those snap over three tabs on the clear part. Just line up the hole for the indicator light over the raised part of the clear knob and snap together.

i read page one, and im one of those with a burnt out hvac light. do they just get replaced l.e.d's or is it more critical.

http://scionlife.com/forums/showthread.php?t=158086&highlight=HVAC%2Bissue%2Bfix

should take care of it if it is the common 07 issue