Air Con: Passenger compartment temp sensor

[Rover Saloon]

2000 S80 petrol 2.4 with automatic climate control.

Great - an indian summer and my air con has suddenly stopped working. No warning - just got in it one day and it wasn't blowing cold. Had been working perfectly the day before. Pretty sure it's not the compressor or gas so read the codes. CCM0003 which relates to the blower fan motor passenger compartment temp sensor.

Took the climate control module out and checked the thermistor was still in place and connected with both leads - it was. Noticed that the sensor fan wasn't spinning so stripped it down and cleaned it. Now spins perfectly but still no cooling. The compressor is not coming on.

So my question is, could the thermistor fail and could this be sufficient to render the air con inoperable?

Blower fan works fine as does the heater.

All suggestions gratefully received

[Chris_Rogers]

Definition I have is:
CCM-0003 Evaporator temperature sensor,

This is inside the heater unit next to the evaporator, not easy to change but from memory there's a work around, a search on here should find it.

[Rover Saloon]

Thanks Chris - I got my definition from the Diagnostic tool I have the PPC by BSR but I am sure that your source is probably more reliable. Unfortunately, I think you intended to put a hyperlink in your message but I can't seem to get anything to open?

[Chris_Rogers]

My source was the PPC manual, there are two code definitions for the code mine and yours.

If you say what year & model you have I'll try another source.

Here's a thread:

http://www.volvoforums.org.uk/showth...+sensor&page=5

[Rover Saloon]

Hi again - yes it's a 2000 S80 petrol 2.4 with automatic climate control

Thanks

[Chris_Rogers]

Looked up your year & model and got fault code info which matches your code definition.

Diagnostic trouble code information
Condition
If control unit registers that pulses from fan motor pulse-sensor are less than a certain frequency, diagnostic trouble code CCM-0003 is displayed.

Substitute value
-The fan motor pulse generator is switched off.

Possible source
-Fan motor blocked.
-Wires open circuit or short circuit to voltage supply/ground.
-Defective fan motor.

Fault symptom[s]
-Interior temperature does not match set value.
-Poor interior heating.

I had a further look and could not find a fault code listed for cabin temerature sensor, so it seems this may not be monitored.

There is however a procedure for checking it:

Checking the interior temperature sensor signal
-Ignition on.
Read the interior temperature (using vida/dice) and vary the temperature with the interior temperature sensor to see if the value changes. Also check that the value is correct by comparing it with the values from the outside temperature sensor and interior temperature sensor, UEM or thermometer.
Is the temperature OK?

Here's a thread giving some info on the sensor and resistance values for various temperatures, maybe this info would enable you to check yours.

http://www.volvoforums.org.uk/showth...ght=thermistor

[Rover Saloon]

Chris - I do apologise for not coming back to say thanks for your incredibly detailed post. I have had to travel North to look after some poorly parents and so I have had to put further investigation work on hold whilst I am away. As soon as I get back I will get onto it.

I really value your posts and am so grateful that you have given me so much help so far. Leave it with me.