Am I missing something? Ambient Temp Sensor

[300kplus]

The external temperature sensor is located on the passenger side under the front bumper.

Here's a close-up.

So I just replaced this on my E39 and no change in the temp.--still reads "-40*"
Does it require a reset of sorts?? Please advise.

Thanks.

[jamesdc4]

Read the quoted posts.

DIY:
External (Ambient) Temperature Sensor Replacement

The ETS placement on an E39 is shown in the following thread.
Where is the External Temperature Sensor located?

If your temp reading is still -40°C after several days, you may need to try this...

Netstat is correct - you need to short the terminals to calibrate the sensor. I had to do the same thing. With the car off, bend a piece of wire into a "u" shape, and short across both terminals. After it is in place, turn the key to the "on" position, while still on, remove the wire and plug in the sensor. Check the display, the temp should then be correct. Also, the climate control will not work right if the temperature is reading -40.

Depending on the amount and kind of damage done to the wires, you may need this kit.

That depends on what is at the end of the wires. If the ends are in tact then just the sensor is needed. If the ends are frayed, cut, or otherwise damaged, then I would suggest that in addition to the sensor, you pick up Bavarian Autosport's External Air Temperature Sensor Plug Repair Kit (part number 61138365340KIT):



You can buy the passenger's lower engine compartment cover, the external temperature sensor, and the wiring repair kit for about $122 USD before shipping.

If you use the kit, there are some additional instructions that you'll need to follow to get the sensor working. The following is the best description of the extra steps, but as more data becomes available, I'll update this post.

I bought the kit from Bavauto and had the same issue.

It's been a while, but I think the sensor itself comes as one piece but it is actually two, and you have to take the inserted piece out, and then open it up, in order to get the connector ends of the supplied wires all the way into it.

Carefully examine it and you will see where it comes apart. I almost felt like I was breaking it. The connectors on the ends of the wires end up all the way at the end of the plastic male piece when they are inserted properly, then the male piece goes into the female temp sensor itself.

I then just crimped the wires onto the leads. According to "bavarian otto" the polarity is not important.

Good Luck

Fixed. The female plug Bav Auto provides is three pieces; a gray piece, a green piece, and a white piece. I pulled them all apart and once I too the white piece off the wires simply slipped in. Simple instructions saying to take all the pieces apart would have saved me a lot of time and cussing. Oh well. Thanks for the help.

]

[christiansBMW]

I paid 9$ on eBay got a new sensor and plugged it in . And within 2 minutes it was reading the right temp. And all I did was change out the little sensor part no wires or anything . Mine read -40 for over a year

[300kplus]

Read the quoted posts.

So the plug is still on the end of the two wires like it should be normally so all I did was replace the old sensor with a new one. Are you saying I need to put a wire in a "u" shape into the two plug terminals following the instructions?

[jamesdc4]

So the plug is still on the end of the two wires like it should be normally so all I did was replace the old sensor with a new one. Are you saying I need to put a wire in a "u" shape into the two plug terminals following the instructions?

No. I'm suggesting you might want to try the method eva89 mentioned worked for them. I would also want to make clear to try this at your own risk, as the author of the DIY posted at the top of my quoted thread didn't have to do anything extra to get the sensor to register the correct temp after installation.

Good luck and post back the results for others who might run into the same problem.

[300kplus]

No. I'm suggesting you might want to try the method eva89 mentioned worked for them. I would also want to make clear to try this at your own risk, as the author of the DIY posted at the top of my quoted thread didn't have to do anything extra to get the sensor to register the correct temp after installation.

Good luck and post back the results for others who might run into the same problem.

Yeah, I'm not ready to take that risk just yet What else could it be-I plugged in a new one and I'm still at -40 upon start up. I do have some bulbs out in the cluster. I wonder if that has anything to with it?

[ME264]

In lieu of spending money for a temperature sensor I calibrated a series of resistors that I got from Radio Shack...

Open circuit = -40F
100Kohm = -26F
10Kohm = 50F
1Kohm = 122F

So, for the fall I'm putting a 10Kohm resistor on the wires. This winter I'll try a 33K and maybe in the spring I'll dump the cash for a new sensor.

[noodlesandsam]

I got a used one from RIBoater out of a car he was parting. With connector and pigtail. $25 with postage. Why bother with a radio shack kluge?

[ME264]

6 cents vs. $25 bucks... That's why.

[Emory39]

check the wiring thats what happend to me

[cwise12]

In lieu of spending money for a temperature sensor I calibrated a series of resistors that I got from Radio Shack...

Open circuit = -40F
100Kohm = -26F
10Kohm = 50F
1Kohm = 122F

So, for the fall I'm putting a 10Kohm resistor on the wires. This winter I'll try a 33K and maybe in the spring I'll dump the cash for a new sensor.

You own a 540 and you can't spend $25 on a sensor?

[AMGlol6]

You need to actually drive the car. The temperature will not change while the car is stationary. BMW does this to keep temps from fluctuating excessively while driving. It might take a couple miles for the temperature to begin to move towards actual ambient temps.

[bluewater530]

Short the two wires and then just wire normaly and drive temp will go to temp within a couple of minutes
Don't ask me how I know 1st thing that I had to do to get ac working properly

[KevinMullins]

In lieu of spending money for a temperature sensor I calibrated a series of resistors that I got from Radio Shack...

Open circuit = -40F
100Kohm = -26F
10Kohm = 50F
1Kohm = 122F

So, for the fall I'm putting a 10Kohm resistor on the wires. This winter I'll try a 33K and maybe in the spring I'll dump the cash for a new sensor.

While I would still opt to just replace the sensor, this is still good information for testing purposes. I personally like knowing details like this.
Like the OP, he plugged in a new sensor and it still wasn't reading right.
Throw a resistor in there real quick, see if the gauge changes accordingly, now you at least know it's not a wiring or connector type issue and can move on to trying to reset things or just drive it, or any of the other methods mentioned, etc, etc. (personally I think all you need to do is plug in a new sensor and it should start working, it's really nothing more than a variable resistor, but whatever)

[ME264]

You own a 540 and you can't spend $25 on a sensor?

Normally I don't rise to the bait...

I have 5 kids under age 12, an austin healey 3000, a 540i, an M5, and a honda for the masses. A Ph.D. in Electrical Engineering, a 4 car garage with a lift in the house that my trophy wife and I built with our own hands.

I try not to spend money on things I don't need. Given that a NCT thermistor is about $2.00 I thought I'd calibrate what was supposed to have been placed under the front air dam right where the PO ripped it out.

YMMV,
Larry

[bluewater530]

Show us the trophy wife
Lol

[300kplus]

No. I'm suggesting you might want to try the method eva89 mentioned worked for them. I would also want to make clear to try this at your own risk, as the author of the DIY posted at the top of my quoted thread didn't have to do anything extra to get the sensor to register the correct temp after installation.

Good luck and post back the results for others who might run into the same problem.

Okay. Can't say for certain why it works but it does. Maybe it just needed to be started and shutoff a couple times as that's all I did. Works fine now.

[n1gh7mar3]

Show us the trophy wife
Lol

I agree! Some picture are needed to help prove your point!

[rf900rkw]

In for pics of the Healey.

[djb2]

The real reason to spend the $15 and replace it properly: keep the connector contacts sealed.

My sensor was missing when I bought the car, so I don't know how long the contacts were exposed to the elements. I installed the replacement sensor, and it didn't work.

The fix was disassembling and replacing the connector shell. The original shell had a broken latch and had gathered a coating of road grime. Once the shell was off, the connector contacts were easily cleaned and the replacement shell installed. The sensor worked immediately on the next drive.

Note that I did not solder on new contact pigtails. I left the original wiring and crimped contacts in place, doing all of the work at the wheel well.

BTW, the I don't know where the superstition of shorting the harness contacts came from. It's not going to reset the computer. The only thing it could do is clean the contacts.

[Der Krieger]

Normally I don't rise to the bait...

I have 5 kids under age 12,

They know what causes that ...

[aspensilver540]

In for pics of the Healey.

+1, my dad still regrets selling his to raise me (bad trade he says, even though I break down less)

[EditTim]

I'm dealing with this right now.

I just finished doing major work (timing guides, oil separator, valley pan, etc.) right before I had to go into surgery for an f'd up left arm (I'm right handed, fwiw). Well, as I was driving out of the hospital parking deck a week later, I clipped a low curb and the temp sensor as gone.

Initially, I went to the local dealer and forked over roughly $60 for a new sensor, the connector, and the two wires.
I had my brother install it. Next day I noticed the temp read 70° F and all was well.

Until the next day. -40° again. WTF. At home I got under the car and could see the sensor was gone again (bad install). Grrrr...

This time, I ordered the same stuff from Pelican, with a Febi sensor instead of a "BMW" sensor (which I assume is the same) for about $40 shipped.

Sensor came quickly, and same brother installed senser, making sure it was secure.

This time, no temp change, still -40°.

Sensor is removed, and I take apart the connectors. One of the two terminal pins in the sensor was way shorter, as though it broke off. I know I was careful putting it together, and I didn't see any remnants of the broken terminal anywhere, but whatever, I'm sure that was the problem.
Reviews on Pelican reveal several mentions of fragile terminals, and DOA sensors, so there you go.
Pelican sent out a new sensor today for me.
Check the sensor for both terminal health, and resistance as described above.

BTW, I never saw any slow ramp-up to correct temperature after replacing the sensor the first time, not like my old e32s, it displayed the proper temp before I even got the car on the road...

[Qsilver7]

Okay. Can't say for certain why it works but it does. Maybe it just needed to be started and shutoff a couple times as that's all I did. Works fine now.

As someone mentioned in a previous post...the ambient temp sensor is buffered to prevent constant temp changes. Ambient temps are not the same everywhere at the same time...position to sun or shade...height or depth all constantly influence ambient temperatures. Think of your home...standing beneath a large shade tree vs standing on your driveway or patio at high noon...the north side of the house is always cooler than the southern exposure...as well as the east side vs the west side at the same time of day.

And if the temp sensor wasn't buffered...those that live where temps drop below 37 degrees F would go batty with the ICE WARNING going off every few minutes that the temp would rise to 43 degrees, then back to below 37 degrees.

[jamesdc4]

In for pics of the Healey.