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hello,

anyone know if there is any fuse for the outside temp sensor?? i had to splice a new sensor in my 98 s500 due to the old sensor ripped out on the car wash impact along with the front bumper( collision) and now the temp in the dash reads -36*F 24/7 after splicing the other sensor in.
 

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Must splice? insturment bulb?

Not the help you wanted as my new merc lost the sensor and I want to take one from the old car and replace. Will I have to splice or is it possible to take out the sensor and wire to a connection point?

While we are on the subject of temperature sensor. Both of my dashes don't have a working bulb for temp and odometer read out. I've got the feeling that is some kind of permantently saudered in bulb. Anyone have advice on this?
 

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See if I an answer both questions ! I do not believe there is a fuse! Not sure what kind of sens you bought but make sure you have made a good connection! Mine was kind of a POA to connect. And yes there is a soldered bulb for the temp indic. I can't remember the number other than very tiny and I got it from Rad Shack. Pull the dash and the indic just screws out. A fine sold iron and you melt the contacts on the board put in new bulb and resolder. Not a hard job at all!! Mine still goin strong! Good luck!!!


Smokie
 

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Resistance is the sensor

hello,

anyone know if there is any fuse for the outside temp sensor?? i had to splice a new sensor in my 98 s500 due to the old sensor ripped out on the car wash impact along with the front bumper( collision) and now the temp in the dash reads -36*F 24/7 after splicing the other sensor in.
Most temp sensors rely on resistance within the circuit to calculate the temp.

When a splice is made, that can change the effective resistance of the circuit.
 

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Has it been reading like this for more than a day? I just spliced a new connector to the outside temp sensor on our BMW. It went from reading -40 deg (open circuit) to reading -35 deg immediately after repair. It had to sit overnight before equilibrating to ambient temp. The circuit has some kind of time-averaging algorithm built in that allows it to change the temp reading only slowly, so it takes time to get to the ambient temp reading if the sensor has been disconnected.

If yours has been like this for more than a day of driving, I'd look for a problem. Is there a difference between the -36 reading and the open circuit reading? If yes, then at least you know the circuit has "recognized" a closed circuit to the sensor. But, then I wouldn't have any idea why it would not have equilibrated unless there is a problem with the sensor or wiring.

Brett
 

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You guys are burning up a lot of air time over a part that cost about $60 from the dealer. For the whole thing, sensor, wire, guaranty.

Then of course, if you want to diddle around with this some more, carry on! But know what you're diddling with.
 

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You guys are burning up a lot of air time over a part that cost about $60 from the dealer. For the whole thing, sensor, wire, guaranty.

Then of course, if you want to diddle around with this some more, carry on! But know what you're diddling with.
I have to admit I didn't understand why a replacement was being spliced in, unless it was snipped out from the junkyard.
 

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You guys are burning up a lot of air time over a part that cost about $60 from the dealer. For the whole thing, sensor, wire, guaranty.

Then of course, if you want to diddle around with this some more, carry on! But know what you're diddling with.
Good grief, man. Perhaps you would like to let us know just what we are "diddling" with if it's not an old cheap car.

Brett
 

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Hey... I said it was ok to diddle.

You're just trying to resuscitate a $60 part, not a far more expensive one, and I thought you might want to know from someone who simply went out a bought one and installed it, simple as pie.

I know some of these cars are old and cheap. Those that diddle with stuff like this will only have old and cheap cars. Their cars will always be 'ghetto-fabulous', because they take the time to make the patchwork repairs, instead of working towards making the money needed to get the job(s) done right.

I see it here on this forum all the time and it used to be comical. Now, it's just sad that beautiful, former $100k+ cars are turned to crap because a number of us feel it 'isn't worth it' or 'can't afford it', so they do it all on the cheap.

So Brett, you are correct. While some of us own 'old and cheap' w140's, there are a number of us who don't.

That doesn't make our advice less valid, does it?
 

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Outside temp

All the outside temperture sensors are wired into the harness, there is no plug to unplug and replace, this is why he has to splice the cable. This is on W140s that I have seen. Stryker, maybe your thinking he means in the instrument cluster? He means the unit in the front that clips on the tow hook cover... Is this what you replaced?
 

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My outdoor air temp sensor read -36 F when I bought the car.

There was a short in the wiring. When the resistance in the circuit is near 0 ohm, the temp will read -36. I fixed the wiring in my car, and now I get correct temperature measurements.

Try examining your wiring, and search the rest of the harness for shorts. Do you have a multimeter? You could measure the resistance of the sensor, see if it has any resistance. Good luck!
 

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Hey... I said it was ok to diddle.

You're just trying to resuscitate a $60 part, not a far more expensive one, and I thought you might want to know from someone who simply went out a bought one and installed it, simple as pie.

I know some of these cars are old and cheap. Those that diddle with stuff like this will only have old and cheap cars. Their cars will always be 'ghetto-fabulous', because they take the time to make the patchwork repairs, instead of working towards making the money needed to get the job(s) done right.

I see it here on this forum all the time and it used to be comical. Now, it's just sad that beautiful, former $100k+ cars are turned to crap because a number of us feel it 'isn't worth it' or 'can't afford it', so they do it all on the cheap.

So Brett, you are correct. While some of us own 'old and cheap' w140's, there are a number of us who don't.

That doesn't make our advice less valid, does it?
A simple thermistor is an unlikely part to fail, particularly one that is encased in a protective cover that is the outside temp sensor on these cars. They have to be tough because they're right there up front exposed to the elements and debris strikes.

If there is a wiring issue distant from the sensor itself, you can pay your dealer to replace the thing 20 times if you want to, but you won't solve the problem, and you won't have learned anything or taught anyone else anything in the process.

You'll notice 95_S350D has offered a far more informative response without any condescending and uninformed editorializing. You could learn from his approach.

Being the owner of three of the nicest W140's on the forum hardly qualifies one as a giver of advice on how to fix things. I fail to see the connection.

Brett
 

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The previous owner of my 1999 was involved in a minor accident involving the front end. The bumper was pushed in. I didn't know of the accident when I bought the car. The problem involved two things when I took possession of the car: the park-assist and the outside thermometer wedged in the driver's side tow-hook. The park-assist didn't work properly and the thermometer gave wacky readings.

This is how I fixed my problems (watch carefully, Brett):

I had the bumper taken off to determine that one park-assist sensor was missing and the park-assist wiring harness was broken. I eschewed the attempts to repair a missing sensor and broken wiring harness, opting instead, for new parts. The thermometer I couldn't find anything physically wrong with the sensor portion, but the wiring got pinched somehow and instead of diddling with what's broken or damaged, I opted instead to buy a new part (pleasantly surprised it cost only about $60), complete with the sensor and about 4 meters of wire that plugged into the car's body harness.

I solved my problems with new parts that were reasonably priced instead of horsing around with chipped/clipped/compromised pieces. And I haven't had a problem since.

Problems solved. My way.

And that's how I fixed my issues. DONE!
 

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There is a lot of strange info on this,,, all temp sensors read 38c when faulty. A re soldered connection into the harness does not make for a high resistant joint.

The resistance of the sensor will change with temperature, thats how the thing works.

I must have answered this question 50 times before and I have never had anyone not get it working if a new one is used.
 

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The previous owner of my 1999 was involved in a minor accident involving the front end. The bumper was pushed in. I didn't know of the accident when I bought the car. The problem involved two things when I took possession of the car: the park-assist and the outside thermometer wedged in the driver's side tow-hook. The park-assist didn't work properly and the thermometer gave wacky readings.

This is how I fixed my problems (watch carefully, Brett):

I had the bumper taken off to determine that one park-assist sensor was missing and the park-assist wiring harness was broken. I eschewed the attempts to repair a missing sensor and broken wiring harness, opting instead, for new parts. The thermometer I couldn't find anything physically wrong with the sensor portion, but the wiring got pinched somehow and instead of diddling with what's broken or damaged, I opted instead to buy a new part (pleasantly surprised it cost only about $60), complete with the sensor and about 4 meters of wire that plugged into the car's body harness.

I solved my problems with new parts that were reasonably priced instead of horsing around with chipped/clipped/compromised pieces. And I haven't had a problem since.

Problems solved. My way.

And that's how I fixed my issues.
"I opted instead to buy a new part (pleasantly surprised it cost only about $60), complete with the sensor and about 4 meters of wire that plugged into the car's body harness" Could you post some pictures of where it was plugged in? Im confused on the plugs location....
 

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Eddie A: The wire for the temperature sensor is one piece with the sensor. IOW, the wire runs from the sensor in the tow hook cover, up and through the engine compartment, tying into the body harness near to the fire wall on the driver's side. The connection itself is buried opposite and under the hvac blower motor, amongst other things.
 

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This is the quote you said" I thought you might want to know from someone who simply went out a bought one and installed it, simple as pie." You still saying you installed it yourself? and as easy as pie?...Its very hard to believe you didnt have the dealer do it. By chance would you have the part number of the one you installed? It must be in your service records correct? pictures would help me believe this fairy tail..lol :)~ love bustin your balls...
 

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A 001 542 26 18 .SENDER UNIT
OUTBOARD TEMPERATURE FEELER
 

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Thanks, TV!

Hey Eddie, just run your hand along the line that runs from the sensor. You'll find it soon enough. I was in my indie's garage when we did the work. He may have actually pushed the connector into place, but I was working with him threading it through! Didn't take photos, Ballabuster! I DO remember not having too much slack in the wire, so if anyone thinks they can snip a part off, you'll wind up short.
 

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The 140 seems to be the only model where the sensor does not plug in.

its only shown on the engine / body wiring section.

I have one computer down today otherwise I would have printed off the MB instructions on this
 
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