Wirsbo Thermostat


My friend has 5-6 Wisrbo 80465 thermostat broken (2017).

I looked one.

It has all kind of electronics inside.

I started to draw a schematic diagram.

I put 24VDC to pin 2. Actually it was using 24AC power, but it works also 24DC.
I put to pin 3 LED + 470R resistor to show when load is on and other end to pin 4 (gnd).
I put ground to pin 4.

When I measured it, I found that double SMD-diode D3 was broken.

I replaced diode, which was marked A7W with similar BAS70 diode.

It started to work.


My friend gives me a three broken thermostats more.


All have a broken diode D3, BAS70.

A new thermostat fail

I got a new broken thermostat in 15 October 2019

In one thermostat was R13 broken ( 220 ohm resistor).
It was 0805 type (

I replace it with 1206 type, it has two times more power ( from 1/8W to 1/4W).

I gave the unit to my friend.
At evening I got a phone from my friend.
All powers in system has gone away!
Three other thermostat was out of power.

He was checking the power supply with his voltage meter.
I asked what range he was using.
He said that DC power.
No, it was wrong, it is AC range!

I asked if he has open the power supply, before he was installing wires( four wires).
No, he replied.
He has done short circuit while installing wires

I asked him to open power transform and check the fuse.
It was blown.
The next day he got a new 0.2A fuse ( 5*20 mm) from his working place and he replaiced it.
I got to my phone a message "Every thing ok. Thank you"

At July 2018 I got three other thermostat, same make, which were also broken.

One has all the diodes broken and R13 open, and IC1 broken.
Maybe the power supply has designed badly.

Other has D3 and D1 open. D4 was shorted.

The last has IC1 open power circuit at pin 4, the PCB circuit was some how open, also D4 was little, but only little short circuit.
It eats power.

I changed to all the diodes to better quality type.

I found a manual, but it is not enought

At February 2020 Juha took contact, that his Wirsbo thermostat blinks.
Can it repaired?


The simplest work may be to change this electrolyt capacitor E1 220uF 25V.

Juha after two days:

I changed that capacitor ja no blinks any more.
Now it lights bright when is need for the warm.

The led starts to go dimmer when the potentiometer is turned to cooler.
The finally led go off, when the pot is at coolest position.
That dimming had not happened before.

The floor starts to heat and it feels thät the actuator keeps the ventil open when the led light darker.
I have not looked directly from actuator, but floor feels now warmer.
Thanks for the good tips, Pekka
Now it's not a pity if the thermar could have been repaired!

Pekka moc.liamg|odg3ho#moc.liamg|odg3ho

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