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  #1  
Old 11-18-2009, 11:30 AM
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Outside Temp Display is wrong temp

1991 350SDL

A week ago the outside temp display seemed to be accurate. Now the displayed temp is about 20 to 30 degrees F too high. The sensor is mounted behind the license plate and has not moved itself to a warmer location for the winter.

Has anyone else experienced an inaccurate temp reading and figured out what the problem was?

Thanks,
Greg

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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO
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  #2  
Old 11-18-2009, 01:34 PM
F18 F18 is offline
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Quote:
Originally Posted by GregMN View Post
1991 350SDL

A week ago the outside temp display seemed to be accurate. Now the displayed temp is about 20 to 30 degrees F too high. The sensor is mounted behind the license plate and has not moved itself to a warmer location for the winter.

Has anyone else experienced an inaccurate temp reading and figured out what the problem was?

Thanks,
Greg
Greg.... that is an odd one! I have seen the temp displays sometimes reset to Centigrade which would show lower digits than the normal Farenheit temp scale. Usually that occurs when someone hits and holds the wrong botton or a battery is disconnected for a while.
Most of those temp sensors just quit working when defective.
Are you looking at it after the engine is parked and idelling for a while?....which would be influenced by rising engine temps. Does it settle back to normal while driving?
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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K
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  #3  
Old 11-18-2009, 01:41 PM
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Did you block your grill recently? I noticed a bit of a change when I did that.

How long have you noticed this change and how much has the car been driven during this time?
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2009 ML320 Bluetec
1985 300CD
1981 300TD


Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD
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  #4  
Old 11-18-2009, 02:46 PM
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I notice it driving at speed were it was accurate before.
No modifications have been done to the car in the last 2 weeks.
No battery disconnects or dead battery.
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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO
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  #5  
Old 11-18-2009, 03:09 PM
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Location: Albany, OR
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Its the WVO it has broken the sensor!

I'd look at the wire coming from the probe. It could have gotten frayed or cut. Does the temp go up and down or does it read a constant number all the time?
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'04 Jetta TDI Wagon
'82 300TD ~ Winnie ~ Sold
'77 300D ~ Sold
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  #6  
Old 11-18-2009, 10:15 PM
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Quote:
Originally Posted by GregMN View Post
1991 350SDL

A week ago the outside temp display seemed to be accurate. Now the displayed temp is about 20 to 30 degrees F too high. The sensor is mounted behind the license plate and has not moved itself to a warmer location for the winter.

Has anyone else experienced an inaccurate temp reading and figured out what the problem was?

Thanks,
Greg
My 1992 300D has the exact same problem.

I have a more important problem with a likely bad injector to worry about. If it's just an injector, then I'll have a look at this issue. Let me know if you find something.

I looked at the price of a new probe and found it didn't make sense (+100$) I think...

Bye,
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'98 E300 Turbodiesel 244 000km
RIP '92 300D 2,5 Turbo 632 859,4km due to engine failure
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  #7  
Old 11-18-2009, 11:50 PM
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Location: Amarillo, TX
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My '93 300D reads exactly 17F low.

It is perfectly consistent at all temperature ranges but it reads 17F low.

I looked into replacing it too but the $100 was too much for my blood too.
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  #8  
Old 01-08-2010, 05:22 PM
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Location: MN
Posts: 1,253
I had occasion to remove the gauge cluster. After I re-installed it, the outside temp gauge seems to be reading correctly now. Must be a microsoft thing, unplug it for a while, plug it back in and turn it on and now it works.
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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO
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  #9  
Old 01-08-2010, 06:26 PM
compress ignite's Avatar
Drone aspiring to Serfdom
 
Join Date: Feb 2004
Location: 32(degrees) North by 81(degrees) West
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Non MB Temp probe for Outside Temp Display

"Somewhere" here I read a how to by "Somebody" on the use of a generic temp
sensor (AT Greatly reduced cost).If/When I locate it I'll post.


ErrrrgrrK ! Here Ya Go !



"barrie is offline
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Join Date: Jan 2000
Location: buckhorn, ontario, Canada
Posts: 101
Sensor Replacement
Ron,

What you get from the dealer is a sensor soldered to one end of a 2-conductor wire. This enables you to replace the sensor cable to the display connector (around the fuse box). Because of the labor involved in routing the cable through the engine wire bundle, many mechanics will just cut-off a piece and splice it to the old cable (not recommended!). Others, to avoid the splice, will desolder the sensor from the new cable and replace the old sensor.

In any event, all you need is the sensor itself which is an NTC thermistor. Units such as the Fenwal #192-302LET-A01 or Thermometrics #EC95F302W are more durable and accurate than the original spec. The Thermometrics unit, for example, lists for $3.75 and is available from electronics suppliers such as Newark and Allied.

Hope this helps.

[Edited by barrie on 02-27-2001 at 04:04 PM]
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Damn, You really can find ANYTHING with "Froogle" and Amazon...

http://www.newark.com/jsp/search/productdetail.jsp?SKU=52F3338&CMP=AFC-GB100000001

http://www.google.com/products?q=+Fenwal+%23192-302LET-A01&aq=f
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Last edited by compress ignite; 01-11-2010 at 12:27 AM.
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