W126 Outside Temperature Sensor
 

Hi Guys,

I just noticed, driving down Hollywood Blvd last night, that the outside temperature, as reported by the lcd in the dash of my 87 300SDL, climbs up when I am idling at rest.When I get rolling again, it comes back down. Is this normal? I never noticed it before, but it's been kinda hot here and I've only had the car for a month or so. I have noticed that it reports hot when it's sitting in the sun too, without the engine on. I thought I'd ask before I started trying to monkey around with new sensors from RadioShack or the 60 dollar item from the mercedes parts guys. Kinda trivial I know...

I'd also like to say hi to everyone, I've been lurking for 3 or 4 months now, soaking up the good cheer. This forum is an awesome resource, and was a great help in me buying my new (old) car, and getting me going with maintenance.

Cheers


Andrew

Where is the sensor currently located? Make sure its behind the plate where its supposed to be and not near the radiator or something.

You should expect it to climb when you are stopped. A few times this summer mine hit 115 degrees when I parked the car in the sun!:eek::D

I've never dealt with one from a MB, although I pulled one to try and install into my 126. But the owners manual for a G35 states the temperature sensor is only accurate while moving (and after 15 minutes of driving if parked).

It's a combination of factors. Here's some of them.

1. On a bright sunny day, the ground and to an even greater extent, the black asphalt, soaks up sunlight all day long. Therefore, at any given point on any given day, if it's sunny or has been... the surface temperature at the ground is going to be degrees warmer than the air temperature a foot above it.

2. The engine probably wafts just a little extra heat out somewhere or another when it's sitting still, no matter if you're close to the radiator or not.

MB should have put the sensor under the rear plate like Jag does.

I'm not too 126-savvy, but the 124 changed the temp sensor in '88 to include a speed input and it delays temp changes when moving slow or stopped.

My 84 has a sensor.... The wire got broken by the idiot body shop it was at... I soldered it back together and taped it all up and it worked for a while.... But know it only shows a + and then on numeral digit and sometimes a funky symbol... Tried re-soldering it......... No go..... The numeral digit does increment up and down with temperature change... I think the LCD is bad... :(

Drat....... I kinda liked it...

But yes, mine wafted up and down too... Though it's most useful for knowing temps when you're traveling, so it's fine as is...... Plus, mine was mounted right on the horn support, so it's really close to the radiator and it wouldn't go up if the engine was running do to airflow from the engine fan.......

Just order a new one, they only cost like $100.