AI sez:

�� Main Relay Locations (1979 240D - W123):
1. Fuse & Relay Box (Engine Bay - Driver Side, near Firewall):

Lift the black plastic cover to access fuses and relays.

Typical relays found here include:

Glow Plug Relay:
Large aluminum or black box, often mounted separately near the fuse box or on the inner fender. This relay controls the glow plugs for cold starts. May have a plug-in style connection or hardwired.

Turn Signal/Flasher Relay:
Small square or rectangular unit, often plugged into a relay socket within the fuse box.

Headlight (Low/High Beam) Relay:
Usually found inside the fuse box, can be separate relays or a dual-function relay depending on the model.

Horn Relay:
Often located in the fuse box or sometimes mounted near the radiator core support.

Blower Motor Relay (for heating/AC):
Can be mounted under the dash near the blower motor or behind the glove box, depending on configuration.

�� Other Relay Locations:
2. Under-Dash (Driver’s Side):

Some W123s may have auxiliary relays for things like the seatbelt warning buzzer or interior lights here.

3. Near Battery or Fender Wall:

Occasionally, especially in diesel models, the glow plug relay or starter protection relays are mounted here.