Replacing Coolant Temp Sensor on E430 - PeachParts Mercedes-Benz Forum

EricSilver · #1 05-04-2018, 09:51 PM

The second nasty surprise: You must assemble the sensor socket!

There are three components: The plastic socket housing; 2 metal plugs (for the sensor prongs); and 2 rubber grommets.

The presumption is that a user will slide the grommets over the live and ground wires; one end of the wires into the metal plugs; crimp the grommet to the plug; slide the plugs into the plastic housing’s respective holes, with grommets sealing the holes against water intrusion. Simple, right? WRONG!! The plugs and grommets are TINY, like grains of rice.

If I was the size of a squirrel, with squirrel-sized hands, that would not have been a problem. So what I had to do instead was:

* Recover the plugs, wires and grommets intact, from the old socket, cutting about 2 inches down the harness
* Strip insulation from ends of old wires;
* Splice one end of old wire to a section of new wire;
* Crimp inline wire connector to other end of new wire;
* Wrap one metal plug with friction tape (to prevent shorting);
* Push the plugs onto the new sensor’s pins;
* Pack the new grommets into the sensor’s cavity (to minimize any plug movement);
* Wrap friction tape around the new wires and part of the sensor housing (effectively immobilizing them);
* Wrap a layer of self-fusing silicone tape (for water resistance);
* Strip insulation from two wires in sensor harness;
* Crimp inline connectors from new wires to harness;
* Slide new sensor into engine and clip into place.

Works just fine.

Using climate control unit data, I observed my fans come on at 218 degrees (F). Running at low speed, they maintain 206 at idle and 184 to 211 in normal city driving. Dashboard needle sat at the top of the “8”on the 80 degree mark, as it has ever since I had the car, so all is normal.

Because the fans came on right as I tapped them with my hand (at 218F) I worried that after shutting the car down they would not start again. However, after running an errand and parking for a bit, they did come on at low speed. Nonetheless, I know they are sticky and may still need replacement.

Finally, I could hear some evaporator hissing, suggesting my refrigerant pressure is low. While adding a small can, I heard/saw the aux fans surge once or twice, so I think the high speed is more specific to the A/C than the engine.