Internal cabin temperature sensor failure / replacement

Just thought I'd write this one up in case it helps someone in the future. Had an issue with climate control where there was no temperature modulation outside of sweaty balls or nippy nips :lol: On Lo the air con was icy cold, but shift it just to 18degC and the heat coming out was like trying to make pork scratchings - just mega heat coming out. Had a bit of a scoot around and noted that there are a couple of climate control sensors but the most likely culprit sounded like it was going to be the cabin temperature sensor - part number 99665324100 - which is under here: Essentially the car thought that it was bloody cold inside the cabin so pumped out really hot air continually trying to bring it up to the climate control set figure - which of course it was never going to reach because the sensor wasn't sensing the toasty testicleness of it all. The part itself is near £300 :wtf: https://www.design911.co.uk/fu/prod136205/Cabin-Temperature-Sensor-Porsche-986---996/# For a couple of cheap electrical parts - rip off. So being cheap like I am, I opted for a used one and got it from eBay for the princely sum of £40 delivered. Swapping over was pretty straight forward - just having to take the vent out, and with the hardest part being getting the vent back in without breaking the little actuator arm that controls the vent closure flap. Pop the little cover off with a plastic interior trim tool and undo this little torx bolt, along with the two that are inside the door shut. That'll get you to here: You can see the sensor there poking out of the metal frame. There's two plastic tabs which you then squeeze to remove it from the frame, and then grab it from the back through the vent space and unclip the electrical connector. Refitting is reverse of removal. Watch getting the vent back in - it's a close fit and I found it best to have the vent actuator arm open so that the rod sits flush to the vent structure and not proud of the end you're trying to force back into its slot. Check that it's all still attached and working before putting the bolts back in. Afterwards I went into the 'hidden menu' and checked what the sensor was seeing - it's option 2c and the read out should be exactly what you've set your climate control to. In my case I set it to 20 and sat in the car for a bit to let it steady up, and hey presto: Sensor also sees 20. Why I didn't think to do that with the old sensor still in place is beyond me :lol: But if you have the same problem then it would be worth going into hidden menu and using that to understand whether it's your culprit before just throwing money at it like I did, especially if you're opting to buy a new sensor and feel the sting on your ring Cheers

It is actually possible to fit this item behind the fan ... https://www.design911.co.uk/fu/prod...sche-Boxster---Cayman---996---997-1H0907543A/ You need to make sure it has a good airflow from the fan ... there is kinda a slot it will fit in with a bit of glue . I know as i've done it .. works fine .

Long time no speak DeMort hope you're well. Not sure what you mean here? Are you saying you're swapped that part into the place of the sensor I've just fitted? The sensor I replaced has a sort of internal fan - I know cos I stuck my finger in it accidentally :lol:

This part is fitted to some models .. it's the same part as yours but minus the fan .. it's also a lot cheaper .. I've fitted this behind the fan and wired it so that it becomes the sensor .. there was a slot it fitted into behind the fan .. i glued it in place and wired it up .. it basically replaces the expensive temp sensor as that's a one piece and part of the fan . I don't remember taking pictures of it as it was a bit of a gamble to be honest .. but it did work . You have replaced yours with a working unit so no worries .. I'm just throwing this out there as a possible solution . Ill have a rummage through my pictures just in case though .

Definitely be interested to see

How do you get to the hidden menu, and what else does it show?

996.1 only I believe, but here's the copy pasta: The AC Climatronic unit is actually manufactured by Audi. There is some sort of serial data stream (not CAN) that allows the AC unit to display engine parameters. Works on early 996s and boxters. To switch from F to C: Hold down the recirculating button then push both the temperature + - buttons. To access diagnostics: Hold down the Recirculating & Air up buttons for 5 seconds. The + - buttons go up and down through the list of "c" codes. The center vent button switches the left display between the "c" code and its actual value. Press the Auto button to exit. Here is a list of what can be seen: 0c - ERL 1c - Oil Temp? 2c - Inside temp. Sensor mounted in the aspirator assembly at the side of the dash. 3c - Outside temp. Sensor located inside the air inlet of the A/C unit. 4c - Outside temp. Sensor located in front grill of the radiator. . 5c - Outside temp. (matches OBC outside temp display) 6c - Coolant temp. 7c - Footwell discharge temp. 8c - Sun sensor (dash top) 9c - Sun sensor. 10c - Passenger compartment fan speed. 11c - Passenger compartment fan voltage. 12c - Temperature mix Flap command 1=COLD, 100=HOT 13c - Temperature mix Flap position 14c - Central Flap command 15c - Central Flap position 16c - Footwell/Defrost Flap command 17c - Footwell/Defrost Flap position 18c - Recirculation Valve command 1=OFF, 100=RECIRC 19c - Recirculation Valve position (feedback) 20c - Vehicle speed in kph, updating only once per second. (real speed, not speed+safety margin as in the speedometer) 21c - Engine RPM in hundreds. This too only updates once per second. 22c - ? 23c - ? 24c - Sun sensor, exterior lights switch & panel lights control (term. 58 & 58d voltage) - used for A/C panel display illum. 25c - ? 26c - ? 27c - ? 28c - Fan speed? 29c - ? 30c - Engine run time in seconds (255 max.)(=0xff) 31c - Timing counter 32c - Displays test 33c - Software version? Mine states 3.4 34c - ? 35c - Outside temp. from inlet sensor (filtered?) 36c - temp?

I had a similar issue last year, over the summer of 2019, I thought the aircon was particularly effective, but didn't think much more of it. Come winter 2019 I realized it was always way too cold in the car. I usually leave it on Auto, so tried messing with the manual controls & deduced the internal temp sensor must have been faulty. Like Arry, I balked at the new price, & took a punt on a 2nd hand sensor from ebay for about £25 & followed similar steps to fix it. Coincidentally like Arry, mine is also a 2001 Lapis C2, (all be it a 996.2) but I'm sure other colours are just as likely to suffer from this

Maybe it's just because Lapis is indisputably the coolest colour? :lol:

@ arry .. I had a rummage through my pictures but as i thought .. i didn't take any .. i was basically trying to fix an issue on the cheap so didn't think to photo it . In short though .. the sensor has failed or gives an incorrect reading .. this unit is the entire fan plus sensor and its stupid money for what it is ... .. i believe its earlier models that did not have a fan .. i used one of these to replace just the temp sensor part . It's about £30 . The original draws air over the sensor .. i used this behind so that it blew air over the sensor . The connections needed are the small red base spade female connections .. they can be found in most kits .. ie .. https://www.amazon.co.uk/Connectors...asc_df_B081PRKZXK/?tag=googshopuk-21&linkCode You literally cut the wires to the sensor , fit the above connections and plug into this cheaper sensor . There was a cut out on the left side of the original unit .. i used that to locate it then 2 pack glue to hold it in place .. any glue will do but 2 pack cures to a drillable state in less than 5 mins . Angled against the fan and air is blown over it ... You could just have it hanging down behind the dash but you would have a degree or two of incorrect reading as the air being blown over it from inside the car is what is needed for it to be accurate .

Top bodging mate. If it works, it works 8) I'll keep it in mind if my second hand one ever fails :thumbs:

I have noticed that the air temp coming out of the cabin fans does not get warm until it is set to "Hi". At that point it gets hot. What is the issue and fix pls ?

Good post. I thought a tweeter lived behind there 🤣

Yes. Since making this post I've had someone tell me they've replaced this very sensor whilst having the same issue you you and it worked. Seems it can fail at either end of the spectrum, ie thinkings it's too hot or too cold.