Mercedes ML270 ML430 ML500 ML55 W163 overheating - Troubleshooting and fix

Mercedes W163 with electric radiator fan. Vehicle overheats when stopped in traffic on hot days. Temperature is normal on regular days or while moving. Troubleshooting and fix.

[@victor4837]

Hi, the red wire, you cleaned the end of, is a power supply to the main fuse box. Power supply to the big fan is another thick read wire with a big plastic nut. This nut is holding a 100 amp fuse for the fan. There may be corrosion to either side of this fuse. The plastic nut gets brittle over tome as well. Ground wire for this fan is screwed to the car body with a 10 mm nut under the right side headlight (driver side in your case) - worth of checking as well. The video clearly shows that fan went to full speed when you actually bypassed the fuse. I would check the fuse. I own an ML 270 cdi with the same fan and I have had similar problems with it.

[@ranat5526]

Thanks for that info, my ml 2.7 is also having the same issue so I'll check the connections as per your comment's.

[@user-cy4dc3dx6o]

Excellent job, thanks man!

[@leodf1]

I have the same fan. Mine was running all the time at medium speed, even on a cold engine. Now it has stopped and doesn't run at all anymore. Main power is good, the controller plug reads 11 volts. Any ideas?

[@282sleeper]

You got more issues than that. That belt for one is so shot. probably tensioner and waterpump as well.

[@samersolimanzahra]

Thanks mate; I wasn’t aware. I have sold the vehicle a few years ago. Now have a GL X164.

[@waltercox2207]

The control fsm module bypass it