Ambient Temperature Sensor

[aayaz]

Quick question....my outside temperature reading is out of whack, it goes from 70 degrees down to 32 and then down to -40 then quickly back up to 70. I believe the ambient temperature sensor is damaged. Can anyone direct me to a DIY for this? Where is it specifically located because when i searched around it seems that i can't find one on the F10 5 series, only an e46 or a e39. Thanks!

[TLK]

It's in the passenger side air duct, sticks horizontally into the air stream. You can see it with a flashlight if you peek in the duct. It's on the side toward the middle of the car. Same old sensor as all the other models I'm sure, you just need to figure out how to reach it from the inside.

[aayaz]

If i take the passenger wheel off and remove the wheel well plastic trim, is it easy to just disconnect the sensor and replace it with a new one?

[aayaz]

So i replaced the temperature sensor this weekend and for the rest of the day saturday and sunday it was working just fine but now (monday) all of a sudden the temperature is just stuck on -40 degrees...any thoughts on what could be the issue? Check engine light came on too.

[arucano]

if it goes to -40 it means there is an "open cricuit". Check the wiring for damage and the connectors for corrosion.
Good luck

[aayaz]

Originally Posted by arucano

if it goes to -40 it means there is an "open cricuit". Check the wiring for damage and the connectors for corrosion.
Good luck

Oh i see. Hmm i didn't see any damage to the wiring or connector but i guess i have to take a closer look. I'll post pics.

[aayaz]

So i took a few photos this evening. the first two are of the connector and sensor. I checked for any wire damage but i didn't see anything that popped out. There is some black electrical tape on it but that's about it. In the last picture there is a small black trim pin that looks like that's supposed to be snapped into a part of the car trim maybe? Does anyone have any thoughts? And if the wiring is completely fried, how do i go about fixing that? Or should i just take it to the shop....

[Dwaynos]

When I had my e39 I had the same problem. I found the insulation split and wires corroded where the loom ran up behind the bumper and under the headlight area. Could be totally different on the f10 though but I doubt it will differ too much.

[aayaz]

Originally Posted by Dwaynos

When I had my e39 I had the same problem. I found the insulation split and wires corroded where the loom ran up behind the bumper and under the headlight area. Could be totally different on the f10 though but I doubt it will differ too much.

Hmm ok, seems like a real pain in the ass. There's also not much room to move around where the headlight and bumper meet. BTW, is there a fuse that is linked to the temp sensor? maybe that went bad? If not, can i actually remove the wiring from the car to lay it out on a table under light to see if there is a damaged area?

[Dwaynos]

There won't be a fuse for that no. It was actually really easy on the e39, the headlight slid out after removing 4 bolts. See if you can trace where that bit of loom goes from there, if it goes up towards the headlight, remove the headlight or you could remove the Airbox to see if you can see the loom there. I would imagine, from experience you are probably not far from the problem. Sorry I can't help any more. I'm not able to look at my car at the moment to see if I can see the routing, I'll have a look tomorrow if i remember.

[aayaz]

things use to be so much easier in my E46 M3. I saw some repair kit on ECStuning.com (https://www.ecstuning.com/b-assemble...65816905133kt/) but don't know if anyone has ever used this and if it actually worked.

[Dwaynos]

I wouldn't bother, when you find your problem simply cut the bad section out and rejoin the wires. Make sure you don't cut to much out though otherwise the wires won't reach.

As you stated earlier, that clip on the loom is supposed to fasten to the body, you may find that because that isn't clipped in, it has allowed the wire to rub on a sharp edge perhaps. Again probably not far from where you are now. If you're unable to remove the front bumper yourself then I would suggest checking as much of the wire as you can get to. Expose the rest of the 2 wires you can see, you may get lucky.

I have to assume you have looked At the connector itself to make sure there is no corrosion or that the terminals aren't spread too far apart?

[aayaz]

yea i looked at the connector, it looks completely fine with no corrosion. Ok i'll try and go up the wiring as much as possible hopefully tomorrow night.

[aayaz]

Update.....i checked the entire wiring and there is no damage at all. I checked the connector too and there is no corrosion, everything looks fine. In fact, the temperature is back to normal now out of nowhere. Although it still drops to -40 a few times a day and then climbs back up to the normal outdoor temp. I zip tied the sensor to the wheel well in a more secure place. Still don't know why it's dropping below zero and then increases back to normal.

[Dwaynos]

It's registering -40 sometimes because you have an intermittent open circuit. You either have a wire somewhere that finds connection every now and again, the connector terminals aren't tight enough or you have a dodgy sensor although this would seem unlikely.