MERCEDES W124 M103 RANDOM OVERHEATING PART 8 

Thanks saw that setup on RU-vid, so far car is not overheating, I basically replaced almost everything, still I never really found what part was causing the issue, tested system when outside temps were in the warm 80's, now its winter colder 60's, what gets me is car has never run hot in 10 years ,then all of a sudden it started, pointing to a bad mechanical or electrical part, mechanical has been replaced, so... if car still has issue could be HVAC pushbutton unit, it may not be sending proper signal to relays, or the block may have deposits, but for now its running nice and cool, the 1978 450SL has the 75F thermostat that fits.

@@mygermancars7264 I'm having some odd electrical issues as well..one of the things I replaced is the voltage regular on the alternator one of the brushes was worn down quite a bit versus the other brush

@@mygermancars7264 i accidentally jump started my car with 240 volt 🤣 ..i checked all fues and nothing was fried not even the voltage protection relay next to the battery .. I'm just hoping it's the voltage regulator ..

Do you know the part number for the fan clutch Thanks

@@EKG1976 www.autohausaz.com/pn/UR-1042000528

Where can I contact you ? I want to do this mod for mine m103 can you help me ?

I've worked on my own cars for years, this issue was strange and difficult for me to diagnose on this car, I did not find one bad part on the car? that's why I just started replacing parts, I figured some parts were just old and it wouldn't hurt, all coolant parts were replaced, still had hot running issues, so next was the electrical part of system, I suspect it was the aux fans not coming on at certain hot temps 115C , hi and low speed relays checked out OK, one part I could not test was the climate control unit in dashboard, according to the schematic, the 2 pin temp sensor on head sends signal to CCU and then sends signal to high speed fan relay, relay then sends power to ballast resistor located by headlight ,then to fans. I read many internet posts to test Hi speed function pull the electrical connection on 2 pin sensor while car is running and fans will come on at Hi speed, mine would not do that, I don't know if the CCU is sending signal or just a design change on my year? one thing I could try ,I have a spare sensor, I could hook it up to electrical connection there at head , without install into head, heat it up with a blow dryer to 115C and see if fans come on at high speed. if they don't I would suspect CCU not sending signal to relay, a really good schematic of system would be helpful, the Low speed function is a completely different system and path, mine works.

FCP EURO