the hooded claw said:

I don't THINK .the OAT temp is related to the Air Con .. it (The Air Con) has a seperate Sensor INSIDE the cabin & there is NO WAY you can "Read" the "Current" air temp INSIDE on the HEVAC screen...you can only read what you set it to...

Click to expand...

kernowdragon said:

The actual temp and the temp you've set the hevac to will be very near to each other if all is functioning properly, as if the aircon can't bring the cabin temp up/down to the set temp within a set time you'll get the book fault showing.

Click to expand...

OXO said:

Well that's the odd thing. outside temp was 7. hevac set to 23. no heat coming out. no book fault display.

Then today it all works fine..

Click to expand...

the hooded claw said:

Yeah thats what Dragon was saying .. just because the OUTSIDE temp was 7 it does not necessarily follow that the INSIDE temp was 7 .. it could have been 20 ... the outside temp sensor could have picked up the "Wind Chill" from under the car .....

Click to expand...

Irishrover said:

Try blowing out the interior temperature sensor, it's located behind the small grille just below the clock. There is a small fan which draws the air over a sensor and the fan can get clogged with dust and fluff etc. which causes it to jam. Good practice to do this whenever you check your tyres, just give it a short blast with the airline.:behindsofa:

Click to expand...

Datatek said:

Is that not a blend motor type problem?

Click to expand...

the hooded claw said:

Naw Data ..what Irish was saying is where the clock on the dash is there is a tiny grill behind that is an Aspheric Motor which sucks air into the vent & gets a INTERNAL temp reading.

Its purposely put there so its out of sight & cannot pick up any Solar gain from the windows ect..The motor runs very slowly & pulls in air from the cabin across the sensor this is then used to ascertain the internal temp for the HEVAC & adjust the blend motors accordingly .

What happens in Mercs is the little grill that the air is sucked thru gets blocked up with fluff & bit & bobs & then the sensor cannot get an accurate internal temp reading & so cannot set the correct Temp/speed for the blend moters to either heat or cool the cabin area.


The OAT sensor (Outside Air Temp) ..is not connected to the HEVAC in any way (other than that it SHOWS it on the HEVAC screen)

Click to expand...

Datatek said:

I know that thanks, but no heat one day and heat the next could be a stuck blend motor, I should have said excercise the temperature range not the distribution range, senior moment Could also be an air lock

Click to expand...

the hooded claw said:

For "Senior" moments I would recomend the following..


Pudding, Chips, Peas & Curry (the pudding being a "Hollands" one of course)

Swiftly followed by A bottle of Seven Up, A Fag & a Fart!!!!!


Way oop Narth we don't get "senior" moments we CRAFT moments ...


C ant R emember A F uckin T hing

Click to expand...