[SOLVED] mcquay air conditioning thermostat

[malik_zohaib]

Hi guys.
I wanna ask if someone knows is there any jumper setting in mcquay air conditioning thermostat so it can remember the user set temperature; means when I set the temperature and off the system after that when I on it again it goes back to the default set temperature not mine set temperature.

the thermostat is https://es.aliexpress.com/item/The-...-air-conditioning-thermostat/32485523390.html

and jumper setting(on thermostat pcb) is :

 

[BradtheRad]

I guess it has a default temperature (which might be 68 or 72 or 78 degrees)? The zero-ohm resistors act as jumpers. The setting in your photo appears to be 111011.

Can you be certain the jumpers set a default temperature? Or do they calibrate the device?

Does the thermostat contain programming for daily/weekly operation, and default temperatures for all programs? Then it seems hard to believe they would give that much real estate to the default temperature alone.

If you feel like experimenting, unsolder one of the resistors. (Notice both ends need to be melted simultaneously.) Power up the thermostat. See if the default temperature has changed. (Also check whether it still reads correct temperature.)

If you find that default temperature changed, then try various combinations at positions J3-J6. Keep notes of results. Success might come with trial and error.

 

[malik_zohaib]

Default temperature is 24C. These jumpers are responsible for auto on and temperature setting.
I already tried few combinations but non of them work. 6 jumpers means 2^6=64 combination I have to try??????
This gonna take forever!!!!!!!!!!!

 

[BradtheRad]

There is the question whether: (a) the device loads these settings only on power-up, or (b) whether it is driven by them continually. That is the reason for my suggestion that you power-up each time you change settings.

It may not be necessary for you to try 64 combinations. Compare the effect when the last 4 positions are jumpered, versus all open. That could tell you a lot.

It is a puzzle about the first 2 positions which have solder bridges. Do they have to do with default temperature? Or Auto operation? You might want to try unsoldering them as well (disclaimer: unless there is a chance that what you do could render the thermostat unusable).

And what about those empty solder pads? Do they go to traces which go to circuitry? Or do you solder unused resistors to them?

 

[malik_zohaib]

By default all jumpers were short but to make system auto ON in case of supply interrupt i unsold J4, and problem solved.
solder bridges were my tries to make system auto ON and save set temperature but so far I cant able to solve the second problem.

J2 and J3 goes to the temperature settings button; but to be honest I'm not sure if combinations of these jumpers works for me but I have a hunch about it.

 

[c_mitra]

There are three "features"- first two show solder bridged over; J3,J6 and J6 are fitted with zero ohm resistors (that are essentially shorts) and J4 left open.

The first two (J1 and J2) set some other variables, I think. They need not be tampered.

 

[malik_zohaib]

Dont know about J1 but J2 n J3 goes to temperature setting, as I mentioned earlier.
The only choice I have, if the combinations doesn't work, is to store temperature value in EEPROM/FLASH and read it when system goes live again; of course I have to use microcontroller with some external connection.

 

[malik_zohaib]

I cant able to set the right combinations but I have successfully able to save user set temperature by using PIC controller (PIC12F675) and some modifications on PCB.