hello all
i have a problem with my outside temp gauge, sometimes it turns on and goes up to 136 and then turns off, sometimes it goes up to around 100 then goes down and then goes up guickly up to 136 again and turns off. Can anyone help me?? thank you

It sounds like the unit has failed. You will need to replace it and possibly the probe.

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Benzmac:
Donnie Drummonds
300E
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM
OWNER OF MB AUTOWERKS .COM

I had a problem with my probe unit also, so I asked this forum for advice. A guy named Barrie gave me some excellent advice. Use the search feature on this site to look up Barrie's listings. He really knows his stuff. I fixed my unit for under 5 dollars!

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Kyle De Priest
1986 300e
1972 BMW R75/5 (Best there is)

The postings you're particularly interested in are dated 11-01-1999 and 11-19-1999.
Let me know if you need anything further.
Barrie

It appears that the thread Kyle refers to is no longer available in the search archive. Perhaps Webmaster Bill can resurrect it?
In addition to the 11-19-99 posting I believe this is the thread that also contains information on the part no. and sources for the sensor.

I keep a file on my hard drive of all the good advice I get for my car. I just happened to have saved Barrie's advice there so I cut and pasted it here...

"If your outside temperature gauge is not working the fault is most likely
with the sensor unit. You can test both the sensor and display by
connecting a 3,000 ohm resistor in place of the sensor. If the display is
working properly then your gauge (with power on) will give a readout of
approx. 77 degrees F (or 25C if you have a celsius gauge).
Having verified that the fault is with the sensor, you need only replace
the sensor thermistor (about $5). However, M-B sells only the complete
cable assembly (the sensor at the end of a long piece of wire, for
about $50), which requires about 2 hours to route - hence the $200
cost. To minimize this labor some mechanics will buy the assembly, cut
off the end, and splice it into the old cable. Spliced connections,
particularly in the engine compartment, are not a good idea! Instead,
you can easily replace the sensor yourself for $5 with no splices. Use a
negative temperature coefficient (NTC) thermistor of 3k at 25C, such
as Fenwal #192-302LET-A01 or Thermometrics #EC95F302W. They are
readily available from any electronics supply house.
If you require more detailed procedures on testing or installation, post
your questions and I'd be glad to oblige."

Good Luck



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Kyle De Priest
1986 300e
1972 BMW R75/5 (Best there is)

Hey Jerzey111,
What type of car are you having this problem with? Finding the probe is half the battle. If you know where it is, it's a piece of cake.


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Kyle De Priest
1986 300e
1972 BMW R75/5 (Best there is)

i have a 86 300e, im going to do what u guys have posted here, and thanx for all your help

Still no word from Webmaster. Do you have the whole thread? I recall it contained some good dialog on sensor location and other replacement issues that I'd like to save. (Or maybe they were in another thread that's also gone.)

I didn't make a copy - assumed (mistakenly) that good procedural stuff of long-term interest would be retained in the archives. Suggest you keep a good backup of your HD as many of us may be calling to draw on it

Our '91 300se temp gauge works intermittently as well. I've traced the wire back to where it enters the fuse box. Where does it go from here? Where is the sensor located to replace?
Thanks,
Steve

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Steve Short
'91 300SE

Well, I don't have copies of the thread... I'm not that organized. I can however re-type basically what I said back then as I remember.

The sensor for the 300e is located under the drivers side front fender behind the headlight. If you put the car on jackstands and get under there, you'll notice the feed wire running behind a rubber box with a single screw in the middle of it (at least I only remember one screw maybe there are 2) If you unscrew that box, it will come off and you'll expose the wire. It will feed into a silver colored metal end piece. Disconnect that so you have freed the wire from the car. Now you can get out from under the car and work on it.

The silver piece should just slip off the end of the wire to expose the sensor. The sensor is at the end of a plastic sleeve. The sensor is super small. I can't believe that this is all it is. The sensor basically looks like a tiny speck with two thin wires coming out of it. Also, as I remember, there is some white jelly/grease stuff all over it. That stuff is designed to keep the sensor from vibrating inside there and also to help transfer heat from the outside world to the sensor itself. Try to keep as much of that stuff on there as possible. Once you remove the sensor from the two leads and the sleeve, you'll notice that the sleeve has two sides to it. This is to keep the leads from touching one another and shorting out. Now that the feed wires are exposed and you can test the system as Barrie explained above. If you discover that the sensor is bad (and when you see it, you'll understand how realistic it is that it could easily go bad), carefully solder the new sensor in it's place. NOW, with the soldering iron, be super careful. This is a heat sensitive piece and it's easy to fry! only use a small amount of solder and only apply as much heat as is absolutely necessary. I bought two sensors (they're so cheap) so that incase I messed one up, I could easily discard it and try again. (Good thing I did, because I did mess the first one up. I think they cost $1.75 each) After the new sensor is in place, check the gauge on your dash and make sure it's working. Is it? Good. Now put it back together and go boast to your wife about how smart you are. That's what I always do.

As far as sensor locations on different cars, I don't know. I have heard that on some Benz's they're under the front license plate. Just put your car on jackstands and crawl under there. You'll find it. This is a super easy fix and it shouldn't take you too long. An hour at the most. I did mine a year ago and it's been working great ever since. If there's anything I've forgotten to explain, will someone please add it. Don't be afraid of this one. Have fun.

Good Luck

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Kyle De Priest
1986 300e
1972 BMW R75/5 (Best there is)

Hey,
I did a quick search of Mercedesshop and I came up with this:
http://www.peachparts.com/ubb/Forum1/HTML/000052.html

It might be of some help. It looks as though there are feeds older than Jan 1, Y2K.

Just a FYI

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Kyle De Priest
1986 300e
1972 BMW R75/5 (Best there is)