Thermo switch

[ado]

What is the purpose of a Thermo Switch and how can i test the old one ?

Thanks...

[Dave at Pelican Parts]

It runs the Cold Start Valve. In particular, it provides the ground for the CSV. When the temperature is cold enough (values vary; I'm not sure why) the single wire that plugs into the TS should be shorted to the threads.

So stick the switch into the freezer for an hour or more, then use an ohmmeter or continuity tester or some such to check for a connection between the threads and the plug. Let the sensor come up to room temp (at least 50F, I think) and check that there is no continuity.

The Cold Start Valve gets its power from the starter circuit, and gets ground through the TS. It will open only when it has both power and ground, so it will only open when the engine compartment is less than 40F (or 32F, or ??) and only when the starter is cranking.

--DD

[ado]

Thanks Dave......

[bowlsby]

More info on this from Brad Anders site. From this you can see that most of the triggering temps are quite low, unlikely that a household freezer can test these because they do not get that cold.

311 906 161 : -12 to -18 deg. C / 10 to 0 deg. F
311 906 161 A : 0 to -10 deg. C / 32 to 14 deg. F
311 906 161 B : -2 to -8 deg. C / 28 to 18 deg. F
311 906 161 C : -6 to -14 deg. C / 21 to 7 deg. F

[Dave at Pelican Parts]

Interesting! I hadn't noticed that information before, Jeff. I had heard figures of "about 40F", which would have been in household-freezer range, but I agree that a lot of the ranges listed are indeed going to be hard to test at home.

Heh, it also makes me feel a lot better about disabling my CSV.

--DD