I'm looking for all the relays on my 1996 E300 Diesel W210.
So far I cannot locate many.

W210 control overview:

Main fuse box is in the rear by the battery under the rear seat. This just contains fuses that are all on the unswitched dc bus (circuit 30) straight from the battery.

Next to the fuse box is the PSE pump. Unlike the pumps in the 124 and 126, the 210 pump also contains controls and relays for most of the devices in the rear of the car.

Under the hood are two control boxes.

The drivers side one contains a major fuse box that carries most of the rest of the electrical loads in the car except for the engine related loads, and the lights. Also in this box are the Front SAM module and a relay assembly. Finally you have the 38 pin diagnostic connector here as well.

The passenger side box contains the engine control module, transmission control module, and ABS control module. There is a relay/fuse module here, this is the dreaded "K40" that contains all the fuses for the engine/drive train control circuits and the starter control relay. This device is an outgrowth of the "OVP" module known from the 123/124/126 models.

I have had the W210 dashboard apart all the way to the firewall. There are no relays or fuses behind the dash, except for the dozen fuses in the side of the light switch that are accessed from the sail panel. Every exterior light in the car goes through one of these fuses.

There is a CAN Bus junction connector under the carpet adjacent to the front passenger door sill. This is where all the CAN Bus lines from the various body modules converge.

Good reading here:
W210 Home Page

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech