Pawel and Chris,
The thermo-time-switch is soldered together at the factory and is not meant to be opened or serviced. It spends its life with one end submerged in coolant, so it must remain sealed. It supplies the earth (ground) to activate the relay for the engine starting aids.
It is fairly delicate inside. A small wire coil is wound around a bi-metallic metal leaf. At the end of the leaf is a set of electrical contacts. When the starter is activated, the electrical coil heats-up the bi-metallic leaf and as it bends, it causes the contacts to open. Since the bi-metallic spring is temperature sensitive, coolant temperature and ambient air temperature also play a roll in the duration of time before the contacts open. The electrical coil in the "tts" receives its earth (ground) through it's housing when it is installed in the cylinder head. The positive current is supplied to the "tts" small "G" terminal, when the ignition key is turned for starting. The purpose of the positive current is only to activate the heat coil inside the "tts". The large "W" terminal of the "tts", supplies earth "ground" to the starting aid relay. When the coil in the "tts" becomes warm enough the contacts open and the "W" terminal no longer supplies earth (ground) to the starting aid relay. If engine coolant temperature is high enough, the contacts of the bi-metallic leaf may stay open and the starting aid relay, will not activate. Since the electrical contacts inside the "tts" use the engine ground from its housing, earth "negative" may only appear at the "W" terminal if the coolant temperature is cold enough and the heating coil has not been warmed from previous starts. Different years of production may have variations in specs. Pagoda engines used starting aids 2 through 5 , depending on the year. Identify and check the specs for your version.
