Whirring hum noise tracked down! Temperature 32c

[g8dhe]

OK probably not the most critical pieces of information ever needed But for the last few months we have been hearing a little whirring hum noise coming from the dashboard area on the passenger side, nothing critical could only be heard with the engine off but with the Ignition on, just detectable during quiet pieces of music with the radio playing.

Turns out to be the Cabin Air Temperature Sensor, its a little PCB with a small centrifugal fan on it and a chip to handle the sensor (thermistor) which feeds the Digital Air Con. electronics.

The centrifugal fan draws air over the sensor from the cabin and runs all the time the Ignition is on, it had just become excessively dusty over the years sufficient to make the noise!
The module can be released by a single screw just underneath it which locks the bracket in place that holds the module and unplugging the cable, easy to remove, a little fiddly to put back as it has to be done be feel.
The module top is held in place by 4 small screws that can be released to give the whole unit a through dusting from the inside which has reduced the noise a lot, might however just put a very tiny drop of oil on the bearing to fully quieten the noise down.

Edited so it can be found more easily in a 'Search'.
Heater, digital, temperature, 32c, cabin, fan, footwell

[Doone]

You're just like Allan, he always has to trace every tiny noise. That wasn't a noise you could have guessed the source of.

[g8dhe]

No way to have guessed it, I'd just spent 20-30 minutes out there trying to identify the location, I had come to the conclusion it was some sort of small fan (not an engine fan), I had the covers up, checked the ECU in case that had a fan hidden away. Then came in and checked the circuits thru when I spotted the Motor symbol in the Temp. sensor module and then popped out again to check and yes with the Glove box removed you can reach it and as soon as I unplugged it you could here it wind down in speed so identified it! But its one of those noises that even with the ear right next to the little air intake slots you couldn't here it any louder - I suspect because the module doesn't seem to actually press against the dashboard but has a foam rim that forms a seal but no actual coupling of the noise to the dashboard...but certainly I hadn't guessed that there was a fan to pull the air thru before.

[Ron Miel]

Good one Geoff - except that you've now got me worried that I can't hear mine Is it working Shan't be happy until I dig it out to check.

I'm like Allan, plus I also have to knw why when I can't hear things which I think are normally there - sometimes it just turns out to be due to age-related reduction of hearing frequency range, so I have to get she who hears everything* to check for me. Always did wonder how that little inlet could reliably feed cabin air to the sensor buried behind it though, although on the other hand it (plus the one top right under the windscreen) does seem to regulate the "climate control" properly. If only climate control was really that simple!

*(Never could get away with quiet mutterings under my breath. "What did you just say?" "Nothing dear". )

[The Great Pretender]

All I ever hear in mine running or not is her indoors giving me grief..................