Temp. Sensor
 

Does anyone know how or know where I can get some info, maybe a DIY, on how to install the ambient temperature sensor on a 95 e320?

have you purchased a new one?

The ambient temp sensor is behind the licence place attached with one 8 or 10 mm retaining bolt. From there it snakes along the driver's fender to just under the fuse box (4 or 6 screws holding the fuse holders and assembly down). There is a connector under there that you'll have to disconnect and reconnect the new one.

On a side note, you have other options. The ambient temperature sensor is simply a 3300 ohm thermistor (resistor designed to maximize resistance changes with temperature) You can order these from www.mouser.com or www.digikey.com for less than $1 ea. Then you can simply snip the end of the OE temp sensor and attach the new thermistor. I drilled the reminants of the old thermistor out of the metal enclosure, soldered the new one onto the two wires, dumped some epoxy in the freshly cleaned out enclosure and stuck the new thermistor in that. Then bolted it back up under the license plate. Good as new.

Also, if you want to test to see if the temp sensor is really the fault, remove the fuse box (take the cover off, then take the ~6 screws out and lift it up) find the ambient temp sensor connector (following the wires from the sensor) and unplug the sensor. Use a 3.3k or 3k ohm resistor across the two pin connector and the gauge should read ~70F or so.

Good luck!

thanks a lot for the information! but what was everyone talking about that you needed to remove the instrument cluster and all that?

I believe on some models - perhaps the w201 (190e) the temp sensor was attached directly to the display behind the insturment cluster.

Ok now I have a problem. The head of the temp. sensor is too big to go through the little channel it has underneath the fusebox...Do I cut the sensor in half and re-connect it? Or do I cut the hole a little bigger?

There's a third choice - find out what's going on. Wrong part, wrong installation method - that shouldn't be.

I didn't end up removing mine, but I thought with the fuse box taken off that the connector/wires were easily removed. Take a pic if you can and post it here, that would help us know what you're referring to.

I agree with the above poster, I would disconnect it and test the display with a resistor to make sure that it was reading correctly. What were the symptoms that led you to decide the sensor was bad?

I took it to the dealer and they said the temp. sensor was bad. So last night, I removed the old sensor and connected the new (I didn't solder the wires to the heads), the temperature reading was still the same, still wrong. Now i'm thinking its the wire/connector that leads down into the cluster underneath all those wires. The sensor was brand new...

What is the temperature reading? Just out of curiousity. If the sensor didn't fix the problem its likely caused by a bad display. I'd suggest eBay as a good source for this part.

The temperature display reading is off by like 20 degress. i.e. It's like 80 outside and it reads 60...? Wait what if the sensor and the display were ok? what about that female connector/wire that leads down under all those wires in the fuse box and possibly to the cluster? Or could it be the cluster itself?

I would definitely test it with a resistor. Go to radio shack or other electronics parts store and get a 3k or 3.3k ohm resistor. Unplug the sensor and put the resistor across the two leads. Turn the key to the on position and look at the gauge. It should read ~70F (25C) constantly (no fluctuations)

If it does, then the sensor is the problem. If it doesn't (and still reads +20 degrees) then its likely the display/electronics contained there.

BTW: The correc thermistor is:

negative temperature coefficient (NTC) thermistor of 3k at 25C

Is this one good? http://www.radioshack.com/product/index.jsp?productId=2062326&cp=&origkw=resistor&kw=resistor&parentPage=search

That would be a good one to test the display with. Yes.

Ok, I tested it and it read 53 degrees fahrenheit...You said that it had to be around 70, which now tells me that the new temp. sensor is fine, and the problem must be the display in the cluster or that connector/wire that goes to the cluster.

e320 95 temp sensor
 

I just tried finding that temperature sensor connnector so that I can test to see whether the temp sensor is bad.

I removed the 6 screws of the fuse box and tried to locate the temperature sensor connector. needless to say there are so many wires and I wasn't able to trace the sensor wire from the temp sensor the fuse box. Therefore couldn't locate the actual connector for the t-sensor. Any further guidance would be appreciated.

Is connector on the right or left of the fuse box. Side or underneath?