OBC Ambient air temp sensor location????

[540iguyy]

Part number for this?? I can't seem to find it anywhere.

Thx.

[Avec]

Check here. If you have the sensor in hand, you can match it up with the correct one. I don't think there is a special connector just for the sensor, so it would be a generic one

http://www.realoem.com/bmw/showparts...90&hg=61&fg=15

[shogun]

Part number for this?? I can't seem to find it anywhere. Thx.

part number for what? The sensor? Or the plug?

sensor is here
65 81 8 350 779

http://img262.imageshack.us/img262/5...psensor6tk.jpg
http://i266.photobucket.com/albums/i...TempSensor.jpg

[jamrobin]

Aha! I got a temperature sensor but the connector was missing as were the brake ducts...
Monkeyed around for a while and thought the sensor I bought was bad...

I finally kludged a temporary connection together using some butt connectors but still saw -37C... Decided to give up for now since it's snowing like ten bears. Drove up to Tims for a coffee and an apple fritter and TADA the temperature reading began climbing.

Important note to anyone replacing this... if it hasn't been connected for some time it will take a while for the reading to change. This confused me because my other e36 SEEMS like it shows the right temperature right away but maybe I just never paid mutch attention.

Still no ducting but I found a place where it's in air flow until I get some (and the pigtail)... Only a 4cyl and I'm giving it to my daughter so I'm in no giant hurry.

[tubbs76]

to this day, I still camt find any loose wiring to connect it to and have no ide where to splice it into the loom. The only 2 wires that look even close are the wires for he fog light.. surely wouldnt be spliced into there???

[Scottburn82]

Old thread I know, I couldn't find it either. There is a hole through the left brake duct where it should sit, maybe it fell out... What is the actual function of this air temp sensor

[K1118]

It displays the outside temperature when you press the temp button on the obc screen

[Scottburn82]

So it's just for telling the driver the temp? Nothing to do with fuelling or anything important?

[K1118]

correct

[jamrobin]

So just to update my own earlier post... I bought a used connector and sensor and installed it last night in place of the kludge I had rigged up with no connector...
To my initial delight the temperature display began to climb up from the -37C that indicated my temporary wiring wasn't good (open circuit).
This morning I jumped in the car (it's about -8C here this morning) and laughed... Apparently the river ice should be melted by noon... it's reading +50C now (122F). I think that's exactly the opposite problem and indicates a dead short in the circuit. I'll pop out at noon and see if it's my connections not as good as I thought, and if they look OK I'll sub in the other sensor after work.

Have to admit I think I'm putting too much effort into something that controls nothing but a display but it's still too cold here to get into the enormous pile of actual meaningful parts I have accumulated in my living room for installation on both the M3 and the 318iS.

[JDStrickland]

The device you are monkeying around with is a thermocouple. It generates current in proportion to the temperature. If you connect it in reverse polarity, the voltage will be wrong. If the leads are not clean, the voltage will be wrong. The device generates millivolts of electricity and milliamps of current. If the connections are not perfect, the information it sends will be wrong. You are not supposed to solder the wire splices because the lead in the solder is a dissimilar metal than is used in the wire, the result is wrong voltage and/or current being generated.

As far as I know, the only purpose of that probe is to tell you how cold it is outside. The most important time for the probe to work right is when the temps are such that ice can form in the shade or on a bridge, and not be easily seen by you as you are driving upon it. When the ground is covered with snow and ice, do you really need a thermometer to tell you there might be ice on the roadway? I think not. The temp probe has a hole in the left brake duct to fit into, if the duct is missing then you need to replace it if you want the probe. I suggest that the missing probe and the missing brake duct became missing at the same moment, expecially since the connector for the probe is also missing. All of this means to me that you should be looking at the lower control arms for signs they are not properly formed to factory specifications.

[tubbs76]

Hi JD, i have the ducts, no temp sensor, i went ot a wreckers and bought one with ample wiring on it. The problem is i cant find anywhere in the loom where it should go.. This is the mystery. So in short, cant fix it...

[toddster8]

FWIW, I bought a new sensor and the sensor plug replacement kit from an on-line dealer. I did have some difficulty getting good connections with butt-splice connectors, since the supplied replacement leads were a couple of sizes larger than the original wires that they connect to. (I checked all the connections toward the sensor and toward the car with an ohmmeter.) I ended up using western-union splices and heat-shrink. The original wires were hanging loose behind the bumper, on the left side, and were the afore-mentioned tan and brown pair that emerged from the same loom as the fog lights and horn wires. What else could they be? The new plug, however, had green/black wires on both sides. If polarity makes a difference, I guessed right the first time.
When I turned the key to position 1, the OBC still read "-37." However, after the car was started for the first time, it started reading the correct temperature. Or maybe two or three degrees higher than correct.
For now, the sensor is taped to a wire loom behind the fog lights. All of the parts associated with "air duct" seem to be missing on my car. As far as I can tell though, from on-line research, there is no separate duct for the brakes specified on the 328iS . Maybe one of the missing bits had a place to mount it. (Got some new ones on order.) But if not, the sensor has a groove that looks like it could snap into any appropriately-sized hole that one might drill into an intake duct.

[c0lin46and2]

FWIW, I bought a new sensor and the sensor plug replacement kit from an on-line dealer.

How much was that kit?

Sent from my Samsung Galaxy Note 2 using BF.com

[johnf]

The device you are monkeying around with is a thermocouple. It generates current in proportion to the temperature. If you connect it in reverse polarity, the voltage will be wrong. If the leads are not clean, the voltage will be wrong. The device generates millivolts of electricity and milliamps of current. If the connections are not perfect, the information it sends will be wrong. You are not supposed to solder the wire splices because the lead in the solder is a dissimilar metal than is used in the wire, the result is wrong voltage and/or current being generated.

From what I have read and from the measurements I took in 1997, the temperature probe uses an NTC thermistor which is resistive and non-polar. I have designed with thermistors and happen to be working on the cold junction compensation and output linearization of a K-type thermocouple – that probe is nothing like a thermocouple!

As far as I know, the only purpose of that probe is to tell you how cold it is outside....

I would not be surprised if an OBC (an 18 button display) also uses the measured temperature to correct its fuel consumption calculations.

[toddster8]

How much was that kit?

Sent from my Samsung Galaxy Note 2 using BF.com

It was about $15. The sensor was $25. Google part number 61131378419KIT and 65 81 1 383 204. Really, you could do as well with some female crimp-connectors and a lot of PVC tape, but this gives you the nice matching yellow socket and waterproof boot connectors.

[johnf]

It was about $15. The sensor was $25. Google part number 61131378419KIT and 65 81 1 383 204. Really, you could do as well with some female crimp-connectors and a lot of PVC tape, but this gives you the nice matching yellow socket and waterproof boot connectors.

I am a fan of sealed contacts over wet and salty roads.

[flyfishvt]

I would not be surprised if an OBC (an 18 button display) also uses the measured temperature to correct its fuel consumption calculations.

No it does not. The only purpose is to display the outside temp on the obc. Thats all.

[jno]

The OEM ambient temp sensor costs silly money, so I replaced it with the IAT sensor I had laying around, fabricated a connector and got the same accuracy for fraction of the price.

[johnf]

No it does not. The only purpose is to display the outside temp on the obc. Thats all.

Soooo, I take it you have looked at the source code.

EDIT: On second thought, strike that. Enough of the temperature effects probably work into the DME's fuel injection time. I bet the battery voltage, which the BMW training material doesn't mention, goes into the consumption calculations because of its effect on the injector response time. The DME could work that in by biasing the "injection time" signal it sends to the OBC, or the OBC could compensate as it does measure the battery voltage.

- - - NEW POST - - - NEW POST - - - NEW POST - - -

The OEM ambient temp sensor costs silly money, so I replaced it with the IAT sensor I had laying around, fabricated a connector and got the same accuracy for fraction of the price.

Off hand, would you know the 25 °C resistance value and the beta value for that sensor? One of the distributors I order from sells some 0.5% tolerance thermistors.

[jno]

Soooo, I take it you have looked at the source code.

EDIT: On second thought, strike that. Enough of the temperature effects probably work into the DME's fuel injection time. I bet the battery voltage, which the BMW training material doesn't mention, goes into the consumption calculations because of its effect on the injector response time. The DME could work that in by biasing the "injection time" signal it sends to the OBC, or the OBC could compensate as it does measure the battery voltage.

- - - NEW POST - - - NEW POST - - - NEW POST - - -

Off hand, would you know the 25 °C resistance value and the beta value for that sensor? One of the distributors I order from sells some 0.5% tolerance thermistors.

Nope, I did all testing the good ol' way by comparing the OBD values to my trusty thermometer.

[JDStrickland]

I would not be surprised if an OBC (an 18 button display) also uses the measured temperature to correct its fuel consumption calculations.

Fuel consumption demands are calculated by the MAF. There is more than enough information about the air quality -- temp and density -- collected by the MAF to set the fuel ratio. The temp probe that lives in the brake duct is watching for conditions that might indicate that there can be ice on the roadway, and the OBC warns you with a chime and a blink when the temp falls to 37F, and then a steady message when the temp is 32F. I live just outside of San Diego, so I don't get to see the OBC display this one very often, the behavior might be a little different than I described, but the point is that there are two levels of warning.

The Owner's Manual states that there is a display and chime if the temp falls to 37.5F. If the temp rises to 43F and then falls back to 37.5F, then the chime and display will repeat.

[johnf]

Nope, I did all testing the good ol' way by comparing the OBD values to my trusty thermometer.

I am just being a little lazy. I will measure the resistance at different temperatures and fit the two coefficients.