Fix for the Limited Climate Control

[AntleredRuin]

Ok so this may be premature, but I've 'extensively' tested it (during a 30 minute test drive) and it seems to work so here goes.

Almost everyone with a Limited with the Auto Climate Control knows that the device gets pretty finicky in its old age, People have to absolutely mash down the buttons sometimes to get them to work (if at all).

After a lot of thread searching (and a scare that I thought was my A/C Compressor or clutch that died; turns out my A/C button just wasn't responding) I dove into the device.
Someone mentioned that he touched up all the solder points and it started to work great after that. I tried this on both boards, front and back, but same issue.
I realized that as I was testing the device before I put the faceplate back on that if I pressed the buttons on the board directly (read: not the plastic labeled buttons) they worked great.
I figured this was because they were slightly worn out after 18 years and wouldn't fully depress when used normally, but when pushed directly, fully depressed. I tested this theory with some electrical tape 'shims' and while it wasn't perfect, it was a whole lot better. So I figured I needed new buttons.

So I hit up a hobby shop here in Houston called Electronic Parts Outlet. This place is pretty amazing. It's like a dozen RadioShacks had an orgy in there. I spoke to the counter guy and showed him the board and he said that he didn't have those exact buttons new, but he has a box of used circuit boards from washing machines and dryers that have buttons that'll fit.
So I got 2 of these for a buck each:

I desoldered a button from the 'new' board and desoldered a button from the A/C so I could test 1 before I fully dismantled it.

As I was removing the button from A/C I had a lightbulb moment.
My method of desoldering is probably not correct, but it works for me, and it led to this idea: Simply melt the solder for each terminal back and forth and wiggle it slowly out so that the button is sitting about 1mm higher on the board than it was. I went ahead and attached one of the new buttons, and proceeded to 'lift' the remaining 6 buttons by about 1mm. I plugged it all back in and proceeded to test all the buttons, and VOILA! It works! It even works great with the faceplate on!

So it appears that the buttons WERE 'going bad'. By lifting them a bit higher off the board, I allowed the labeled plastic buttons of the faceplate to fully depress them. If this stops working for some reason, I'll replace the rest of the buttons with the 'new' ones from EPO, as I put that one fully down and it works just as good.

 

[audiness]

Thank you for posting

 

[PWD4R]

I only liked this for the orgy

Sent from my SM-G935T using Tapatalk

 

[AntleredRuin]

Update:
Well it's been almost a week, and it's still working great. Not sure if this applies to all the issues with the climate control, but definitely worth looking into.

For those who want new buttons;

I'm considering buying more of these boards to mail to fellow T4R members, as the little buttons are a pain to come by. They need to be the EXACT right height, or else the faceplate buttons won't press.
Any takers just need to cover shipping, the board, and maybe a few bucks to cover my time and PayPal's percentage. (I don't want to come out negative)

The boards (at least the ones I saw) come with 6 buttons, and the A/C requires 7, so I'll mail 2 boards. I won't desolder one extra button for you.

Any thoughts?

All disclaimers; I'm not responsible if you screw your A/C up permanently because you can't solder, etc. This is also not a guaranteed fix, just my personal experience.

 

[Jungoes]

I did this exact same replacement, I got the switches from an old mp3 player, switches were fine . this worked for a while and then the problems came back.

Here is where i found the issue:
Behind the LCD panel is a small row of resistors that are loose.
use a small clean soldering iron and just re-do all the connections.
you will have to cut the white plastic box that supports the lcd, bend the entire lcd screen slightly back to get access to it. (sounds tricky but if you take your time it can be done.
that is where the soldering was loose on those small parts under the LCD.
Sorry i didn't take pics. zero issues to date.

 

[AntleredRuin]

That makes sense. How long ago was that?
That may be the next thing to try if this doesn't 'take'.
I did not hit those connections underneath the LCD, as I did not want to cut the white plastic, but that may be why my initial fix did not work. Who knows?

Like I said, no guarantees; this was just my experience.

 

[White Stripe]

Their are a couple company's on ebay that rebuild the climate control unit for about 70 bucks. That's what I did.

 

[fullspeed]

I am having problem with the turn knob for temp. Sometimes I turn knob and temp setting doesn't change. Any fix this?

 

[White Stripe]

I am having problem with the turn knob for temp. Sometimes I turn knob and temp setting doesn't change. Any fix this?

Yes, the same company's on ebay I mentioned will fix that too when they rebuild it.

 

[infamousRNR]

Update:
Well it's been almost a week, and it's still working great. Not sure if this applies to all the issues with the climate control, but definitely worth looking into.

For those who want new buttons;

I'm considering buying more of these boards to mail to fellow T4R members, as the little buttons are a pain to come by. They need to be the EXACT right height, or else the faceplate buttons won't press.
Any takers just need to cover shipping, the board, and maybe a few bucks to cover my time and PayPal's percentage. (I don't want to come out negative)

The boards (at least the ones I saw) come with 6 buttons, and the A/C requires 7, so I'll mail 2 boards. I won't desolder one extra button for you.

Any thoughts?

All disclaimers; I'm not responsible if you screw your A/C up permanently because you can't solder, etc. This is also not a guaranteed fix, just my personal experience.

I'd be down to give this a try...

I picked up an extra one recently to replace mine but I'm unsure of its condition & will need to install it before I know it's "bad"...

 

[AntleredRuin]

I'd be down to give this a try...

I picked up an extra one recently to replace mine but I'm unsure of its condition & will need to install it before I know it's "bad"...

Sure, shoot me a PM with PayPal info.



For everyone, I'm thinking $12 shipped for 2 button boards. Lower 48 only.

 

[ColinNg]

Here is where i found the issue:
Behind the LCD panel is a small row of resistors that are loose.
use a small clean soldering iron and just re-do all the connections.

Mine was so far gone that I had to reflow the board. I have fixed it about 10 times and each time it broke after a really cold night, or for unknown reasons.

If yours is this bad, I’m guessing eBay for the rebuilders is a better deal!

For those so inclined, you can diagnose and reflow your board as follows:

Connect to 12V DC to only the + and G pins as follows:

(view this sideways on some phones)

This is the connector in the rear board of the unit.  
Looking at the pins as they come out of the board side of the connector. 

+--------++-------------+
|........||Go........oCC|
|........||oo........oo+|
+--------++-------------+
==========================//=====  <-- board

Legend:
+  +12VDC
G  Ground (fat pin)
o  fat pin
.  thin pin
C  Constant (fat pins, powered when vehicle is off)

With it powered this way, one can test and catch it breaking without reinstalling it in a vehicle. It takes a tiny amount of power when it’s out of the car, probably less than 200mA. The buttons on mine would work perfectly if I flexed the board at the middle toward the back (i.e. press above the Mode button).

Prepare the board for hot plate reflow:
- unsolder every component that sticks out in the middle section (screen, ribbon connector, capacitor, diode, crystal, 3 switches)
- heat the middle section of the board with reflow hot plate until the components can wiggle (be careful not to displace them!)
- ensure board is flat as it cools down
- solder everything back on

I’ll update if it breaks again!


Indicator Bulbs

- 2x Lamp Assy, Indicator; 81850-35050 (Black base, frame)
- 2x Lamp Assy, Indicator; 81850-35040 (White base, LCD)


The $5 (and $6 shipping, total $11) reflow hot plate I used:

AC 220V 300W Aluminum LED Remover PTC Heating Plate Soldering Chip Remove Demolition Welding BGA Station Split Plate

Ignore that it says 220V; I live in Canada and it works fine with 120V. You just need the appropriate plug and cord (I soldered a connector on to mine, then plugged in a removable appliance cord).

 

[MrMike67]

I used a space-heater to reflow..

It's Jan 2024, and my kid just bought herself a '99 4Runner limited.
Many of the climate-control buttons didn't work right or at all. Especially, when the windows fogged up, neither the front defogger button nor A/C button worked - safety issue!

I removed everything and pulled the two circuit boards from the climate unit.
If you are patient and careful, you CAN do this without breaking any plastic.

I put the boards about 4-6 inches in front of a small space-heater. I placed the two boards with their back-sides (NOT the LCD, NOT the connectors) facing the space-heater. I let them get hot to the touch, and flipped them upside-down (keeping the plastic and components away from the heater) to try to evenly heat them. Did this for about 5 minutes with each board. I did NOT let them get so hot anything would be damaged, but they were hot enough that I could not hold them for too long. I think 5 minutes was enough to soften the solder - no idea how long this will last but all the buttons are (amazingly) working :bluejump:!

For those of you mashing buttons, PLEASE STOP! I suspect it's not the button-mashing that fixes it, but the flexing of that board causing the weakened solder joints to connect.

You can search and confirm, but I think if one used a heat-gun (I do not have one) set at 220C, gradually warmed the board evenly and kept that temp for about 2 minutes (search: reflow solder temp), that could also do the trick. DO THAT AT YOUR OWN RISK.

Fingers crossed this holds up... remind me in 6 months to post an update whether it's still working.