Overvoltage Protection Relay (201 540 3745)

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Overvoltage Protection Relay
2015403745.JPG
Part number(s) 201 540 3745
201 540 3045
Used on 107
124
126
129
201
202
461
463
669

Description

The Overload Protection (OVP) Relay is a relay used to protect the computer components of a vehicle. On the 190E and 300E, it serves to protects the main ECU and the ABS computer. The newer version of the OVP with the red cap has two 10A fuses on top while the older black cap version has only one 10A fuse. Cars originally equipped with the black cap can upgrade to the newer red capped version.

Removal / Installation

W201 / W124

  1. Remove battery
  2. Remove electronics cover behind battery
  3. Unplug OVP relay
  4. Remove OVP relay
  5. Installation is reverse order
OVP relay located behind the battery on a W201

Troubleshooting

ABS light on

ABS light on while engine is running.

If the ABS light is illuminated in the instrument cluster and the engine is running, it is common to find that the culprit is the OVP relay. The ABS computer will not receive any power if the OVP relay is not functioning correctly, therefore triggering the warning light. Check the fuse(s) on top of the OVP relay for any cracks or run a continuity test. Lastly, replace the OVP relay with a known working unit.

Hard to start

Difficulties starting can also signal a bad OVP relay. The main ECU will not receive power if the OVP is not functioning correctly. Check the fuse(s) on top of the OVP relay for any cracks or run a continuity test. Lastly, replace the OVP relay with a known working unit.

Diagrams

Pin-out diagram


See also