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Discussion Starter · #1 ·
I have a 320D 2001 E46, The previous owner hit a bird and ripped out the outside temp sensor. Since then the temp on the dash has read -40 and the on board computer will not work and the heated rear window comes on every time the ignition is turned on. I have replaced the sensor and all plastic guards also reconnected the horn wires but everything is still the same. Does anyone have any ideas how this can be fixed pleaee help!!!
 

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Have you checked the fuses? the heated rear window will come on if the control panel doesn't work or is unplugged
 

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Discussion Starter · #4 ·
Yer i have checked all the fuses and they are fine everything else works as normal. I have read that if the temp drops below -37 it aoutomatically turns the heated rear window on but not sure if that is true. I will double check all the connectors tonight.
 

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Discussion Starter · #8 ·
The fuse is ok so i will check the power to it at the weekend. i connected the new temp sensor to the ends of the cut off wires, these may be corroded so i will try connecting them further along the wire. the temp reading sometimes changes when its raining.
 

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Discussion Starter · #9 ·
I have re-wired the sensor further up the wires all the connections are good but still the temp is -40. I can access the OBC by holding the trip reset while turning the ignition on. I have reset the OBC using option 19 to unlock then option 21 to reset now the display on the dash is showing the clock. Pressing the button on the indicator stalk has no affect. The fuse is ok and when removed had no affect. Does anyone know how the computer works? and where is its brain? are there other fuses or relays? i am completly stumped.
 

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Discussion Starter · #11 ·
Bit of an update! I now know the computer is working because when the engine is running I can access the on-board computer using the trip button and the information on all the options work apart from the temp guage still showing - 40. I might just be a case that the button on the end of the indicator stalk is broken. Does anyone know if i can use a multi meter to test the wires for the temp sensor and how i can do it?
 

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There should be voltage on the end of the temp sensor wires, I don't know if it will be 5 volts or 12 volts(more likely) though
 

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I've done a bit more research on this and found out that the outside temperature sensor is connected directly to the instrument cluster's control unit located within the cluster itself. I have a feeling that this part of the unit has malfunctioned or there is a break in the sensor wiring itself (probably pulled as it lost the sensor). Without this sensor linked to the control unit, the mirrors and screen/lamp washers will be heated constantly on startup.
 

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Discussion Starter · #14 ·
cheers for that, i will try using a multi meter over the weekend I am hoping its just a broken wire somewhere. Does anyone know if the temp sensor not working would stop the use of the computer button on the end of the indicator stalk?
 

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Does anyone know if the temp sensor not working would stop the use of the computer button on the end of the indicator stalk?
That could be down to the stalk itself. They have been known to get dirt between the contacts.
 

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Discussion Starter · #18 ·
Latest Update!!! On the drive into work this morning the on board computer changed from the clock to the temperature then started to count down from -40 and has stopped at -19. When i restart the car it automatically shows the temp again and is on -19. I still need to test the wires ive not got round to it yet. how can the temperature change like that if the gauge isnt working. I have put the new one on about 1000 miles ago and the temp hasn't moved untill this morning. Its so frustrating.
 

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I suspect a faulty control unit eddie :frown. Either that, or it may need some sort of calibration, I'll see if I can find something on this. It also might be an idea to get the codes read to see if anything pops up.
 

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Discussion Starter · #20 ·
My new next door neighbour owns an auto electrical company so i might get him to have a look at it. Where abouts is the control unit then and how much?
 
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