190E #3 Fuse Keeps Blowing
 

Hello MBers,
My problem is the #3 fuse in my 1991 2.3. It's for the auxiliary fan. When I use the air conditioning this fuse sometimes blows
sometimes even though the fans work. Also, at the same time, the temp. sensor for the engine fan, (3-pin, Black, 100c) goes bad. I have replaced this sensor twice. I put my original one back in with no problems (replaced because of age). Could these new sensors (BEHR) be of inferior quality than the original?
Back to the first question. I'm thinking that the auxiliary fan RELAY is the culprit. I can't see why the #3 fuse would blow. What would do it. ??????
Thanks for your input