Wires imbedded in washer hose?
 

95 e300d. Has two windshield washer pumps. The hose that sprays the windshield has two insulated wires imbedded along the length that terminate near where the hose fit into the pump. Where the wires come out of the tubing near the pump, it looks as if the two wires are crimped to form some sort of thermometer or sensor. Is this "sensor" supposed to hang loose or does it belong inside the reservoir? If it belongs inside the reservoir, how does one install it?

Just a guess, but that could be the heater part of the 'heated windshield washer' that is an option on my '94 E320 wagon. Maybe your's heated too?

Good guess
 

This is a good guess, but there already is a heater coil inside the reservoir - circulates warm engine coolant. My guess is that it is a thermostat, but how does one get it into the tank? The only way is through the grommet and with the washer pump, there isn't much room. A mystery?

dtf is right
 

Wires in hose keep hose and washer fluid warm. Terminal crimp and resistor makes wires get a little warm. Adios and thanks.