Help & Advice needed swapping PCB switches around

Thread Starter

john2k

Joined Nov 14, 2019
207
I have PCB as pictured below which is for my car climate control buttons. I have highlighted in red two pairs of switches to increase and decrease temperature. The left pair is up and down for driver and the right pair is up and down for passenger. However, I need to swap it around so that the left pair and right pair are other way round. I was hoping that all the switches were somehow connected to a pin on the connector itself. However, this does not seem to be the case. It appears the ground (which i highlighted in blue) seems to be shared amongst them all including the buttons and the LED's. And there is not enough pins to have a pin for each switch. I think it may work as follows, when you press each button, different resistance values are read by the controller that this connects to. And each resistance value performs a certain task.

So it appears I a now stuck. Anyone have any suggestions of how I can possibily swap these around?
 

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Thread Starter

john2k

Joined Nov 14, 2019
207
Any help?

One possible way I was thinking is to patch the non-ground pins of the pins over from one side to the other like illustrated in red arrows below. But problem with that is there's no way to isolate that leg of the button so that it doesn't touch the contact solder point while somehow patching another wire in. Any suggestions will really be appreciated. Thanks

 

Thread Starter

john2k

Joined Nov 14, 2019
207
And here is a picture of the underside of the board. Can really tell much on the photo and the traces seem very hard to see. Right behind the switch itself, i do not see any traces on the other side

 

Lo_volt

Joined Apr 3, 2014
268
How good are your reverse engineering skills?

It might help to try to draw up a schematic of the board. This will allow you to see how each of the switches is connected and a solution might easily present itself. It should also confirm or negate your hypothesis on how the switches are connected.
 

Thread Starter

john2k

Joined Nov 14, 2019
207
It definately seems like each button press creates a different resistance value which is then interpretted by the control box as a certain action. The only way I can think of is if I can somehow bend back the leg on the button so that it doesn't touch the pcb trace solder point and then use a small thin wire (something like a strand from a cat5 cable maybe) and then maybe route that bent leg to he other side solder point and vice-versa. And then possibly just put some glue around the switch to strengthen it seeing as it will only be held with one leg.

Is that doable? Below is a close-up picture of the button itself, can the button leg be bent upwards and soldered to a wire and prevent it from making contact at the bottom?

 

Thread Starter

john2k

Joined Nov 14, 2019
207
Not ideal. That button is held down by two solder joints. Can you cut the trace?
Unfortunately i cannot see any trace leading to the buttons at all. It's all hidden. If i were to unsolder the one leg, it will make the button weak and held on by single point but then i was thinking to add some sort of glue to the lower section to make up for the lack of support on the other leg. Not ideal and definately not going to be tidy seeing as there will be 4 pair of wires running across. If I bend back that single leg upwards, will it break the contact and give me clearance to still have button in place and solder a wire there instead?

What kind of butons are these? Just thinking if i should buy a few to play around with so i have backup
 

Thread Starter

john2k

Joined Nov 14, 2019
207
The traces run on the reverse side through a via. Use a meter to find them. Or you can stay the course.
There are traces for everything else except the button itself and problem is even if i find the trace and somehow cut the trace and solder to that, the risk is damaging the entre thing. Whereas if i somehow do the single leg bending method and patching with wire, then i can always bend the leg back and put it back to normal if it doesn't work
 

MisterBill2

Joined Jan 23, 2018
12,399
If the resistors are simply switched in by the buttons then it makes more sense to move the resistors.
BUT WHY alter the arrangement of button functions? I find that very puzzling.
 

Thread Starter

john2k

Joined Nov 14, 2019
207
If the resistors are simply switched in by the buttons then it makes more sense to move the resistors.
Problem is that I have no idea which resistor(s) are linked to the buttons because there are lots and mostly related to LED backlights and other LEDS.

BUT WHY alter the arrangement of button functions? I find that very puzzling.
Because the board I have is made for Left-hand-drive car and my car is a right-hand-drive. So those two groups of buttons are located in the wrong seat positon. Meaning, the passeger is adjusting the drivers temperature and the driver has the passengers temperature button.
 

Wolframore

Joined Jan 21, 2019
2,549
Problem is that I have no idea which resistor(s) are linked to the buttons because there are lots and mostly related to LED backlights and other LEDS.
Use a multimeter trace it out, I suggest, like others have suggested, trace it all out and draw a diagram. This one is not that complicated. Chances are the LED's are on only 3 in series, all drawing power from the same line to light them from 12-14VDC.. Get the LED's traced out and then you can focus on the buttons. With that many pins, I would guess that they all have individual pins going to ground.
 

MisterBill2

Joined Jan 23, 2018
12,399
Moving the switches will not have any effect because they are all the same. The solution will be in swapping connections or moving resistances. To do either with any success you need to know the circuit board, or at least the connections to that board. If you are able to connect an ohm meter to the terminals with the board disconnected, then, and if you can keep track of which button does which, it should be possible to determine which button affects which terminal, and then exchange the wires controlling the two sides. That is presuming that it is separate circuits, which it may not be. If you can access the wiring diagram for both models that may show the connections at the connector as being different. So that may also be an option.
 

Thread Starter

john2k

Joined Nov 14, 2019
207
Moving the switches will not have any effect because they are all the same. The solution will be in swapping connections or moving resistances. To do either with any success you need to know the circuit board, or at least the connections to that board. If you are able to connect an ohm meter to the terminals with the board disconnected, then, and if you can keep track of which button does which, it should be possible to determine which button affects which terminal, and then exchange the wires controlling the two sides. That is presuming that it is separate circuits, which it may not be. If you can access the wiring diagram for both models that may show the connections at the connector as being different. So that may also be an option.
Yes I figured moving the switch definitely won't make a difference. all the ground points (outer leg of each switch) seems to all be connected together with 0 ohm reading. As I don't have any documentation to this board and being a aftermarket Chinese product there is no support. Hence why I was suggesting bending back the non-ground leg of each button and then patching the solder point over to the leg on the opposite side and vice versa. This in theory will complete the switch circuit on the opposite sides when pressed. Only concern with this method is that the switch will then be held together only by one leg. Making it weak. Hence why I was suggesting adding glue (maybe epoxy) to provided support for switch to not move or get loose
 

MisterBill2

Joined Jan 23, 2018
12,399
Yes I figured moving the switch definitely won't make a difference. all the ground points (outer leg of each switch) seems to all be connected together with 0 ohm reading. As I don't have any documentation to this board and being a aftermarket Chinese product there is no support. Hence why I was suggesting bending back the non-ground leg of each button and then patching the solder point over to the leg on the opposite side and vice versa. This in theory will complete the switch circuit on the opposite sides when pressed. Only concern with this method is that the switch will then be held together only by one leg. Making it weak. Hence why I was suggesting adding glue (maybe epoxy) to provided support for switch to not move or get loose
The non-ground side of those switches goes to either an IC or a resistor, unless there is a wire for each switch, which i doubt.
So if you know the function of each button, and can remove the whole board to a convenient location, then you can explore with an ohm meter at the connector that ties it to the body computer. With one meter lead on the ground connection, some other terminal will show a resistance reading when each button is pressed. If it happens that there are two terminals, one for the driver side buttons and one for the passenger side buttons, then the solution will be to exchange those two wires in the connector. That would be the very best case. If it is all at one terminal then the solution is a bit more complex.
 

Thread Starter

john2k

Joined Nov 14, 2019
207
The non-ground side of those switches goes to either an IC or a resistor, unless there is a wire for each switch, which i doubt.
So if you know the function of each button, and can remove the whole board to a convenient location, then you can explore with an ohm meter at the connector that ties it to the body computer. With one meter lead on the ground connection, some other terminal will show a resistance reading when each button is pressed. If it happens that there are two terminals, one for the driver side buttons and one for the passenger side buttons, then the solution will be to exchange those two wires in the connector. That would be the very best case. If it is all at one terminal then the solution is a bit more complex.
I'll do some of that resistance testing tomorrow and try and draw up a diagram of what I find and report back
 

Thread Starter

john2k

Joined Nov 14, 2019
207
The non-ground side of those switches goes to either an IC or a resistor, unless there is a wire for each switch, which i doubt.
Forgot to say, there is definitely no IC. There are just a load of resistors scattered around at the back. And at the front there are the buttons and led backlight fir each button. All the LEDs are on together when parking lights are on. There are a few LEDs that only light up when a function is pressed like the defrosting amber led
 

MisterBill2

Joined Jan 23, 2018
12,399
In the best possible result there will be two controls outputs, one for passenger side and one for driver side. If both can use their controls at the same time, that should be the case. Then it will just be a matter of exchanging the positions of the two wires in the cable side of the connector. Possibly tedious, but much easier than moving parts by unsoldering them.
 

Thread Starter

john2k

Joined Nov 14, 2019
207
If both can use their controls at the same time, that should be the case.
I just tried adjusting temperature with both sides simultaneously but only one goes up. Doesn't recognise both of them at the same. The side that goes up is the button that gets pressed the first
 
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