thermal switch..2prong vs 3prong?

[mkehler]

Okay, lame question..but on your typical 80's VW rad (88 Scirocco non-AC 16v in this case) whats the diff with the 2 prong vs 3 prong thermal switch? What does the 3rd prong function as?

thx
Matt

[Ryan Williams]

Three terminal connectors are used with two-speed fans. Low speed (continuity on switch terminals 2 & 3) comes on between 198 to 208 degrees (F). High speed (continuity on switch terminals 1 & 3) comes on between 210 to 221 degrees (F).

[Bill Miller]

Dr. Ryan is right as usual!

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MARRS #25 ITB Rabbit GTI
SCCA 279608

[mkehler]

Thanks guys. Should I assume that with the 2 prong..the fan comes on between 198 and 208 then?

thx
Matt

[Bill Miller]

No, it actually depends on what the switch is set for. I've got a 2-prong that's set for 180.

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MARRS #25 ITB Rabbit GTI
SCCA 279608

[mkehler]

Ahh yes...now that you say it..I seem to recall there being a ' 90 95 ' on the plug..so it'll turn on at 95, off at 90....which my handy conversion dealie says 203 and 194 fahrenheit.

thx!
Matt