When I got my car the outside air temperature was reading high by, I thought, about 4℃. When it read 29℃ on the M4 between Bristol and London in a torrential downpour in September it became evident that it was well out!

The sensor is in the lower radiator grill fitted from behind. The Saab WIS says "remove the panel forward of the left front wheel". Feel free to do that but it doesn't help in any way because the space between the bracket and the bumper is big enough for a small child to get a hand through but not an adult.

I discovered that I could extract the sensor from its mounting by putting an 8mm deep socket over the lugs and pressing hard. The sensor then drops out, held by the wiring.

Disconnecting the plug through the lower grill isn't easy but, would be easier if you attach the sensor to the centre vane of the grill with a cable tie.

Attach a second cable tie, a long one, to the wires close to the plug, don't cut off the tail.

Using a small screw driver lift up the locking tab and pull the plug from the sensor, then pull the tail of the cable tie to get the plug through the grill.

With the plug on the outside connect the new sensor and then, gently, ease the sensor and plug back through the grill.

Now comes the hard bit, align the sensor with the hole in the mounting, from the inside, and press it home. You can now cut the tail off the cable tie.

Finally, get hold of the old sensor and cut the cable tie holding it to the grill. Now ease the sensor through the grill.

Easy when you know how!

When I did it I didn't attach the old sensor and it flew off the connector and rested on the inside of the front bumper, it stayed there for some 150 miles but migrated behind the radiator, where it was relatively easy to extract.

WIS has a table of resistance values against temperature, at 20℃ mine was 4.6KΩ, it should be 6.24KΩ the curve is parabolic not linear.

The sensor part number is 25 775 833