J type thermocouple. This is the standard sender used with the VDO cylinder head temperature gauge on all Jabiru engines. This sender is supplied with a 4mm ring and screw which can be attached between the spark plug holes on a Jabiru engine. The hole would require tapping to 8/32 UNC, taps are available. Our part reference CHTPLUG is the plug complete with pins that mate to CHT Sender with12 abd 4mm rings making removal of ram air ducts and senders much easier. This sender with other ring end terminal sizes can be supplied by special request. Some aircraft have been found to be incorrectly wired, if you find a CHT sender not working, reverse the polarity on either the back of the gauge or the sender socket. Don't alter the sender plug as that is correct. The cold junction of the CHT sender should be stable at around 22 deg C, so for every degree higher at the cold junction the gauge will display 1 degree lower and vice versa. Bespoke lengths can be made to order.