I did several searches and did not find. I have a 1983 300d turbo and the electric fan is not coming on. so unplugged the fan and hooked to a battery and it works. Is there a relay for this? if so where is it located?

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If everyone was the same, this would be one boring world.

1937 Chevy pu
1983 300D Turbo (250K) Daily driver
1983 300D Turbo spare motor(250k)
1965 Chevy C-10

should be in the fuse box. what makes you think it needs to come on?

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I am new to the Mercedes 300d but when driving with ac the car temp well above 80. And was told with other makes when you turn on the ac the electric fan should come on and it does not.

__________________
If everyone was the same, this would be one boring world.

1937 Chevy pu
1983 300D Turbo (250K) Daily driver
1983 300D Turbo spare motor(250k)
1965 Chevy C-10

and the only thing I find in the fuse box is fuses (the one on the firewall under the hood)

__________________
If everyone was the same, this would be one boring world.

1937 Chevy pu
1983 300D Turbo (250K) Daily driver
1983 300D Turbo spare motor(250k)
1965 Chevy C-10

Not on a W123. The aux fan relay is on the top of the left wheel well, usually under a black plastic cover. A/C compressor relay is there as well.

"Car temp" is not a factor in aux fan operation.

That's not quite correct. The fan is actuated by refrigerant temp as sensed by a switch on the a/c receiver/drier. Low refrigerant levels will prevent the temp from reaching the trigger point.