Where is outside temp sensor? - PeachParts Mercedes-Benz Forum

tino · #1 08-01-2005, 03:08 PM

My outside temerature gauge used to work and now has gone crazy - it now shows temperatures of 50 C and more. Tried to find the outside sensor behind the front license plate and in general behind the bumper but can not find any wiring or sensor. Where can it be?

JerryWagner · #2 08-01-2005, 03:28 PM

your looking in the right place attached is the manual page for your vehicle

G-Benz · #3 08-01-2005, 03:30 PM

The sensor is fastened onto one of the screws (left screw if you're facing the bumper) that holds the license plate frame in place....black in color.

Actually, I believe the dash unit is more prone to problems than the actual sensor. I went through the trouble to replace the sensor and painstakenly routed it like OEM, only it still yielded the same results...

TimFreeh · #4 08-01-2005, 05:19 PM

In the earlier W124's the outside temperature sensor is mounted on the bumper on the left hand side of the bumper. I've always removed the sensor when taking off the bumper, I'm not sure the sensor can be removed without removing the bumper.

G-Benz · #5 08-02-2005, 05:52 AM

Removing the bumpercover just behind the license plate will reveal a hole large enough to get the sensor out from the bumper...the rest of the looming process is a little trickier.

As I stated earlier from experience, it's usually the dash indicator that goes bad, not the sensor wire...

tino · #6 08-02-2005, 09:28 AM

Quote:

Originally Posted by G-Benz

Removing the bumpercover just behind the license plate will reveal a hole large enough to get the sensor out from the bumper...the rest of the looming process is a little trickier.

As I stated earlier from experience, it's usually the dash indicator that goes bad, not the sensor wire...

Did all that and removed the rubber cover from the hole but did not see a sensor or any wiring.

skiier3_9 · #7 08-02-2005, 09:44 AM

Interesting...perhaps thats why its not working

I'd check behind the bumper to see if the sensor has become lodged back there. My car was doing about the same thing (displaying 136F or nothing at all) and it was the sensor. I replaced it with a $1.00 3k thermistor and it has worked well ever since.

S320drvr · #8 08-02-2005, 11:29 AM

I'm having problems also with my S320 outside air temp. On my old W126 it was right behind the license plate and was pretty obvious. Does anyone know where it is on this car? The only thing that looks remotely like it is mounted vertically between the two fans and looks like a lipstick case with green and brown wires. Is that it or should I keep looking?

john berry · #9 08-02-2005, 11:29 AM

Do you know what the sensor looks like? Go into "Fastlane" at the top of the page click on your year and model, then go to "Body Electrical", then to "Ambient Tempature Sensor" check out the picture. Maybe you can spot it then.
My 88' 300ce reads 136 degrees. Havent had the guts to tackle the job.

G-Benz · #10 08-02-2005, 11:32 AM

Quote:

Originally Posted by john berry

My 88' 300ce reads 136 degrees. Havent had the guts to tackle the job.

Go for it...takes about a hour if you work as slowly and methodically as I do...

G-Benz · #11 08-02-2005, 11:35 AM

Quote:

Originally Posted by skiier3_9

Interesting...perhaps thats why its not working

I'd check behind the bumper to see if the sensor has become lodged back there. My car was doing about the same thing (displaying 136F or nothing at all) and it was the sensor. I replaced it with a $1.00 3k thermistor and it has worked well ever since.

Tell us more regarding this "thermistor"?

I've heard of this fix, but I don't know what a thermistor is.

Mine reads off (+- 11 degrees) or doesn't work at all. Obviously, replacing the sensor wire didn't do the trick...

S320drvr · #12 08-02-2005, 12:03 PM

Quote:

Originally Posted by john berry

Do you know what the sensor looks like? Go into "Fastlane" at the top of the page click on your year and model, then go to "Body Electrical", then to "Ambient Tempature Sensor" check out the picture. Maybe you can spot it then.
My 88' 300ce reads 136 degrees. Havent had the guts to tackle the job.

Thanks John, I didn't think of that. The pic does not look at all what I am seeing so I have to continue my search for this little bugger.

tino · #13 08-02-2005, 01:46 PM

Quote:

Originally Posted by skiier3_9

Interesting...perhaps thats why its not working

I'd check behind the bumper to see if the sensor has become lodged back there. My car was doing about the same thing (displaying 136F or nothing at all) and it was the sensor. I replaced it with a $1.00 3k thermistor and it has worked well ever since.

The sensor on my 1986 300E is mounted on the lower side of the drivers side front bumper. You can see the tip of it but I don't know how to dislodge it. Any ideas?

TimFreeh · #14 08-02-2005, 03:21 PM

You might want to read post #4 in this thread.

skiier3_9 · #15 08-02-2005, 03:30 PM

Quote:

Originally Posted by G-Benz

Tell us more regarding this "thermistor"?

I've heard of this fix, but I don't know what a thermistor is.

Mine reads off (+- 11 degrees) or doesn't work at all. Obviously, replacing the sensor wire didn't do the trick...

At the end of the wire is a thermistor (a resistor that varies resistance with temperature) The correct value is 3K thermistor (3K at 25C i think) and what I did was cut the end of the wire as close to the metal tube surround, soldered the leads of the thermistor to the wires. Then I BET'd the wires so they didn't short on each other. To mount it on the car I drilled all the old thermistor out of the metal tube/mounting bracket peice, filled it with epoxy, shoved the new thermistor in there and let it dry. Then I bolted it back onto the car and it looks like new (and works well too!) No more 136...it actually reads correct now.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Bad Coolant Temp Sensor?	sjsfiji	Tech Help	1	05-25-2004 04:35 PM
Temp Sensor on air intake	67_280SE	Vintage Mercedes Forum	4	03-25-2004 09:26 PM
coolant temp. sensor	fgaeta	Tech Help	1	12-08-2003 05:44 PM
1996 C220 Outside temp Sensor Location	Randy L	Tech Help	1	11-27-2003 10:13 AM
Intake Air Temp. Sensor Question	rainmaker	Mercedes-Benz Performance Paddock	7	08-21-2001 09:38 PM