twin speed cooling fan

[stagg65]

Ok here goes, my t25 1.9 diesel is fitted with the later rad which only has the single thermo switch.
The connector has a three pin set up which should allow the slow and fast speed .
But when the fan cuts in it only runs on full pelt which is fairly loud.
Ive tried putting a piece of wire across the terminals to see if the slow speed works but only one selection works which is the two outer prongs.
Im wondering if there is some way i can modify it so it only runs on the slow speed.
Plus the thermo switch cuts in when the temp is at correct level, so im going to change it for a new one.

[California Dreamin]

If the wiring is original then the thermo switch sounds faulty..
I replaced my two speed switch a few months ago.....slow speed would click in with sporadic 'BLASTS' of full speed, like one second every 3 - 4 seconds...the new switch cured the problem.
You should only ever hear the first speed unless the ambient temperatures are very high or you are working your engine very hard at low speeds (slow speeds = reduced air flow through the rad) ie driving up steep gradients for 10 minutes plus.
Martin