Ok, just how do you test a thermo time switch?

I have bounced around here today with questions on cold start replacement and several brought up the thermo time switch as a possible problem to a bad cold start problem. Unfortunately, I have seen nothing in Haynes aside from the cold start valve and air valve test procedure. Just how do you test the thermo time switch and pardon my ignorance but how does it come into play with the cold start component process.
Thanks...

BR
'73T CIS

Follow this link http://www.pelicanparts.com/ultimate/Forum3/HTML/002666.html

It is a previous thread on the subject.

Basically, the thermotime switch, senses the engine temperature, and when cold enough, turns on the cold start injector while the engine is cranking (only when the key is in the start position). It will also limit the amount of time that the injector sprays to under 8 seconds.

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Bill Krause
'79 911SC Euro

BR,

At some temperature under about 105-107 degrees F the 'W' switch terminal should be closed to ground, the body of the terminal ... and above 115 F or so it should always be open.

The 'G' terminal is the resistance heating element and should be some fixed amount around 20 Ohms or so. If you apply 12 V. to the body and terminal 'G' while monitoring continuity from the switch body to terminal 'W' ... within a couple of minutes, the circuit should be broken.

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Warren Hall
1973 911S Targa

The simple quick-check, if you can get to it, would be to pull the connector off the cold start valve, put a voltmeter or small light on it, and have someone hit the starter. I'd also pull the fuel pump relay so the engine does not start.

If the plug is getting voltage while the starter is engaged, then the cold start valve should be operating. At least this will work if the fuel pump relay is not part of the thermotime switch.

But Warren's method is more complete and will provide more information.

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Santa