Identify micro switch and where to supply

Thread Starter

PeterJan

Joined Jan 7, 2022
2
Hi component engineers. Could someone identify the very small switch on this PCB in the red circle and where I could supply a replacement. The PCB is a heat controller from Kromshroder. The switch which normally works like a push button is broken. You can see the spring that was inside the switch enclosure. If I could find a replacement, I could repair my heater and have my house heated again. Thanks so much in advance

IMG_0516 - Copy.JPGIMG_0517 - Copy.JPG
 

Irving

Joined Jan 30, 2016
2,546
More info needed:

Dimensions, pad spacing,
Is the switch normally on or off or is it a changeover - I can see there are two traces to the switch at front right and back left but are there any others?
Is the switch a momentary (push/release) or a push-on/push-off type?
How much travel on the 'push'? and how long was it? Can you show the other bits of the switch?
 

Thread Starter

PeterJan

Joined Jan 7, 2022
2
Thanks Irving.

Dimensions, pad spacing
Length 5.5mm, Width 3mm, Height 4mm. Switch has four pins 4mm spacing (see picture of bottom face of PCB).
Is the switch normally on or off or is it a changeover
Normally off (open) I believe. Temporary push.
I can see there are two traces to the switch at front right and back left but are there any others?
Yes, traces underneath - see picture. The two top pins and the two bottom pins are connected. I believe that makes for the equivalent of a SPST (NO) switch temporary push if I understand how electricians would call that.
How much travel on the 'push'?
Approx. 3mm
And how long was it? Can you show the other bits of the switch?
Don't know because the broken parts are lost. Only part I found it the little spring that was inside. Visible on the pictures.

Additional info:
The switch is pushed down by closing a door. The door has a little stud that pushes on a cylinder (not part the switch), which in turn pushes on the switch - see picture. I believe that closes the contact. It is held pushed down as long as the door is closed. If the door is open, the contact is open again. That drives a display mode which displays different information whether the door is open or closed. Because the switch is now broken, the display remains in mode "door open" all the time, making the heat controller unusable.

PCB is for a heat controller from Elster/Kromschroder/Honeywell, model E6.0634, but I have not found any way to contact those manufacturers and get any information. There seem to be no repair channel. Distributors and heater companies say just buy a new heat controller (500-600 euros). But it is better to find a new microswitch and repair. Much better for the environment.
 

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Irving

Joined Jan 30, 2016
2,546
Looks like this is a very specific part, certainly not something generically manufactured. Are there no markings on it at all? Nothing remotely similar comes up on any search on the main suppliers. Its possibly a Honeywell proprietary part though it isn't in any of their catalogues.

my best suggestion is to get a 4.5 x 4.5mm or 6mm x 6mm standard tactile switch off eBay/amazon, with a long actuator, cut the pins on the old switch to leave the through board connections and solder the new switch onto the pads, tweaking the pins to fit. If you get a long enough actuator you can then carefully trim it down with a fine hacksaw or dremel cutting disc to suit.
 
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