Thermistors and odd objects in CCMs

Hi all

Suspecting the thermistor in my 2004 MY S60 was faulty I set out to remove it. Having taken the PCB off the rest of the works a thing like a small-signal diode fell out of the temperature sensor tube in which the thermistor is mounted. There is no mounting for it on this tube.

The thermistor proved to be OK, but having cut its leads to test it I'm replacing it with one from ebay with a virtually identical thermal coefficient, +/-1% tolerance (the now unobtainable original has +/-5%) and 7 sec response time (original 3 sec, but I shouldn't think that matters).

If you buy one make sure it has a 25 degC value of 10,000 Ohms (10k) and a "B" (beta) rating of 3435 for the correct thermal coefficient. B=3900-4000 is tooo high.

The "thing like a small-signal diode" can't be one because it has the same conductivity in both directions : DMM set to range 200 ohms, reading "1"; DMM set to 2000 ohms or higher, reading "0". There's no indication of polarity, but apart from that it does look quite like a small-signal diode with a gap in the middle of a copper filling. Anyone have any idea what it is and from whence it came ?

Hope this interests someone :)
keith

Hmm, have you got a pic of it?

Have you seen this thread?
http://www.vpcuk.org/forums/showthre...ord-of-warning

Attachment 32104

Here's one (originally of a diode) I found on the net and modified - the white space in the middle of the actual object appears to contain nothing, zilch, nada. Maybe it's some gas, xenon or radon, say :cuckoo:.

The aircon works a lot better with one of the thermistors mentioned in my OP, in the CMM, and without That Thing.

Yes, I've seen that thread, thanks, DD.

Quote:

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Originally Posted by MistralS60

Attachment 32104

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Your attachment is invalid, so can't be seen.

For those that don't have a clue what this thread is about, here's a fix thread WITH nice glossy pictures!!

https://www.volvoforums.org.uk/showt...ght=thermistor

Sorry it's invalid ; it's an ordinary .jpg.

My OP was really meant to help anyone with the same problem with the temperature sensor (a thermistor) in the Climate Control Module (CCM). The rest was curiosity, as I know what most electronic components look like and how they should measure.

The thermistor with which I replaced the original measures almost identically to the original at temperatures from +38 to -28 degrees C, and we reckon the air-con is now working properly for the first time in years !

For anyone who's interested, according to this video (watch for 0:37 / 2:00, blink and you'll miss it) https://www.youtube.com/watch?v=mFhovSdOY3g
the strange device is an intake air temperature sensor.

The mass airflow (MAF) sensor may have one, but the climate control module (CCM) apparently doesn't need one as there's nowhere to fit one.

Quote:

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Originally Posted by MistralS60

The mass airflow (MAF) sensor may have one, but the climate control module (CCM) apparently doesn't need one as there's nowhere to fit one.

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Really?? You sure about that?

For a CCM to function correctly, it will need to know the cabin temperature. The temp sensor on all P2 cars with Climate control, is fitted behind a small fan built into the CCM panel.