[Jake58]

Your fan problem sounds almost like your thermal switch isn't working. This switch is located in the lower right side of the rad. It will have a plug with 3 wires plugged into it. I believe the red\white and red\black colors are for the 2 fan speeds and a red wire for power. You could test this switch I guess by taking it out and dipping it in boiling water to see if you get any continuity between the contacts. The wires run up to relay located in the upper right side of the rad as well. You might want to check the connections there as well. Also check the fuses. I think No. 13 fuse (10 amp) and No.19 fuse (30 amp) in the panel are for the fan. Seems like every Jetta Diesel with AC from this era has a fan problem. I just bought 1990 and it has a fan problem which I hope to tackle this week. Good Luck