I’m not sure whether my auxiliary fans are working. What could be the issue here. The fans turns freely and the temperature gets 20 degrees hotter when I turn the A/C on.

IIRC the fans are controlled by the ACC unit.

Have you checked fuses?

Sixto
98 E320s sedan and wagon
02 C320 wagon

Ive seen engine temps rise even with aux fans running. How do you not know if it is working? Believe you can jumper if nothing else to verify operation, but lifting the hood with the right things onshould provide indication if the conditions are right.

How is your fan clutch?

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

I think you can jumper the fans via the temperature switch at the top front of the cylinder head, near the upper radiator hose outlet. IIRC there are three pins. The two together are for the low speed and high speed? Ground one at a time to the third pin, should make the fans fire up. I'll go verify real quick on my car.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

I was wrong. On my '95 E300, there is a two-pin connector at the temperature switch, located front of cylinder head near the radiator hose outlet. Start engine, stay clear of the fans, and pull off that connector. On my car, both the fans immediately started up in high speed.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC