PJmak

When exactly are these fans supposed to kick on?

I was told they are supposed to always be on but their speed changes with the temperature of the engine. Mine only come on when the AC is on and they are on full blast.They dont come on AT ALL at any other time.

What I did to try and solve this is replace the relay that sits inside the fender and make sure the fuses are fine. Next I want to replace the coolant temperature sensor but Im not sure exactly where it sits.

Can someone show me where the sensor is and shed some light on how these fans are supposed to function

cm60k

Only one fan will operate when you switch-on A/C, both will working when temp. reaches (90c) or A/C gas temp. become higher than (88c), [[that of course depend to the country spec]]..!

First, you have to check the gas, cause gas sensor has directly related to the Aux. speed function,

make sure temp. sensor is working, and plug not move or loose,,

also, if "gas tank sensor" or "gas pressure sensor" not working properly, it will interrupt the signal in Aux. fans controller..!!

ZAYED,,

PJmak

Thanks for your input man.

Where are these sensors locates?

cm60k

Temp. sensor located left side of thermostat,,

and gas tank sensor & gas pressure sensor located behind driver side headlight(both attached to the gas tank itself)..

ZAYED,,

Ausmbtech

Aux fans should be working together, not separately. They will mainly come on for the A/C. If the A/C condenser pressure exceeds 15bar then the fans will gradually ramp up to full speed as the pressure increases. I don't think they run for the engine until the engine temp exceeds 98-100C (can check if you need the exact figure).

If the fans are running excessively especially when the engine is still warming up then check both the condenser pressure and temp using the A/C control panel. If the pressure is high (18+bar) but the temperature is low (

cm60k

Depend of country heat range my friend..!,

"Gulf/Japan" spec., is differ. than "U.S/Aus/South African spec"..!!

ZAYED,,

Ausmbtech

There may still be market differences but this is the basic specs for the W202 Aux fans (2 in front of the radiator)

Maetar

HI all - I'm an amateur mechanic at best. Would someone please advise how to get to the aux fan relay that is inside the fender? And also let me know exactly what the relay is called so I can order it from www.mbdirectparts.com? Thanks for your help!

DRBC43AMG

If I understand correctly, the unit is the round alloy canister in the middle of the photo

cm60k

I think you mean Auxiliary Fan speed controller Relay, isn't..?,

located in driver side fender arch (behind protective liner..

-;ZAYED;-

DRBC43AMG

Yes that's better. OP talked about behind the driver's headlight
Thanks Zayed.