Mercedes-Benz Forum banner

Two temp sensors?

31K views 10 replies 6 participants last post by  grohgreg 
#1 ·
I have been meaning to ask this question for a while. It is probably stupid, but I should know the answer before I screw something up. There appear to be two temperature sensors on the driver's side of the engine block. One has a wire that goes to the pre-glow relay. The other has nothing on it. Why is there two?
 

Attachments

See less See more
1
#2 ·
What is allowing yout Coolant Temp Gauge to work?

I am not sure where the Sensor is but I have read on my 300D it the temp gets above a certain amount the Electric Cooling Fan in front of the Radiator goes on (it is also supposed to go on when the A/C us turned on).
 
#7 · (Edited)
I am not sure where the Sensor is but I have read on my 300D it the temp gets above a certain amount the Electric Cooling Fan in front of the Radiator goes on (it is also supposed to go on when the A/C us turned on).
OT but FYI, that sensor switch is screwed into the side of your 300D refrigerant receiver-drier/accumulator (located in a hole, just forward of the right front wheel well). When it senses refrigerant temp in excess of 140F, it switches on that electric fan in front of the condensor. Once the refrigerant cools down, the same switch turns off the fan. Don't know what the switch off temp is though, sorry.

//greg//
 
#4 ·
Okay, I will investigate this a little further tomorrow, but the rearmost sensor has a plug that connects to a wire that runs into the glow-plug harness. My coolant temperature sensor works fine.
 
#8 ·
I also wondered about this. This morning, I installed my new coolant temp. sender on the left-hand side of the engine, right at the thermostat housing, but that didn't fix my inaccurate temperature gauge that was reading 50 or 60 degrees C. Disconnecting or reconnecting the wire had no impact on the temp. gauge. The wire connected to this sensor is brown. Here's a shot:



I checked my electrical troubleshooting manual and it shows that the wire from the coolant temp. gauge should be green, so I went and explored some more. I found another sender on the right side of the block, right next to the glow plugs:



This one did the trick (but now the temp. reads almost 100 degrees C, pretty consistently). What's the other sender for?
 
#9 ·
First off, the first pic is on the right side of the engine. Left and right on a car is always taken
from the drivers perspective. I'm not pickin' on ya, just explaining to avoid confusion. ;)
The sensor in question is for the blower motor, to delay the blower from running until the engine temp reaches 40C.




Fish
 
#10 ·
Why are you making fun of me???? :) Just kidding...thanks for clarifying. I actually debated which way to explain and decided on that since it was from my perspective. Noted and will use the proper orientation from now on.

So I haven't heard my fan come on...Should I check something then?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top