Find the a/c dryer, it is behind the headlights on the passanger side i think in a 123. Then pull the wires off of the temp switch on the dryer and connect them together when you turn the key on the fan should come on. If it works just rig up a switch so you can turn it on and off.

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82 Rabbit diesel (first d), 84 Jetta turbo d (300k when sold), 83 240d (305k when sold), 84 F250 6.9d w/Banks turbo(parts truck), 86 F250 6 cyl.gasser(waiting for 6.9d), 84 300d ( 347k Sold 8/04), Y2k New Bettle TDI (185k miles), 95 740IL (wifes), 87 300TD (206k Sold 7/05), 05 Passat TDI Wagon