How to Replace the Grouphead Thermocouple

The grouphead thermocouple swap is a bit tricky, but doable.

REMOVAL

Cut the old sensor wires at the fiberglass insulation, near where they enter the 18-pin connector, past the braided stainless. (No need to cut through the stainless braid.)
Pull the stainless wire up through the hole in the top plate.
Unscrew the sensor from the grouphead using a 7 mm or 8 mm hex (we’ve seen both styles used).
Remove the sensor pins from the 18-pin connector. Do this carefully to avoid disturbing/damaging the sensitive boiler thermocouple wires.

INSTALLATION

Thread in the new sensor by hand only.
- Do not use a wrench. Over-tightening can shear the sensor off in the grouphead, which would require returning the entire machine for repairs.
- The sensor only needs to be snug enough to read temperature - it’s not a structural fastener.
Orient the wire properly.

The braided cable is slightly oval (two wires inside).
When threading, “clock” the oval so its long axis runs up/down.
If needed, loosen slightly to achieve this orientation - better slightly loose than overtightened, stripping the sensor off.
This alignment makes routing through the hole easier

Feed the wires through the hole.
- Position both small connectors side by side and feed them through together. Do not attempt one at a time.
- Use fine-point tweezers to push on the metal connector (not the wire) to guide them down. Avoid stressing the crimped joint.
Route the wire correctly.
- Use a thin screwdriver, long Allen key, or 90° pick to help pull the wire out between the front cover and boiler insulation.
- If necessary, flip the machine, remove the base plate, and take off the front cover to access it.
- Ensure the wire passes between the fill tube and the boiler, not around the outside of the fill tube, otherwise it may be pinched between the tube and front cover.
Reconnect the new sensor wire into the 18-pin connector.

Here's what the grouphead thermocouple looks like running from the GH through the top plate