Porsche Enthusiasts Club Forum

Hi, My heating within the cabin has un-consistent heat. At start up there's heat as temperature is set, however, after a 20min's drive I start to get the heat dieing down and giving a mixture of outside and some heat. I did notice most time the footwell heat is sort of consistent compared to the rest of the blown air.

The front screen demister has consistent heat at all times. I have replace a new heater vacuum valve.

Any advice why I get un-consistent heat?

Thanks

Check this post by Mr. Barbeast which has some useful information regarding cabin temperature sensors - I have the same problem, but have lived with it ... I might have another look at it soon though.

G

Mine does the same. Common issue. There are 3 thermistors. One at the dash sucker next to cig lighter. One behind central cabin air vent and one on the end of a sensor to the drivers side of the blower box in the scuttle. They are pennies to replace. Those will be the culprit.

Stuart

Same here, mine can't make its mind up but it's not too bad so I live with it... A job I must get round to at some point though.

Hi Stuart, do you have any part numbers for those thermistors? Or state which one would be the common one which would fail?.

I don't sorry. Rob Wright tipped me off and I bought a small pack from RS components. I can't for the life of me find them to check. I will look again. Could be a any of the 3 thermistors tbh. Check the resistance of a new one, at the same temp, with your old ones, and you should pinpoint the culprit fairly quickly.

When I say same temp, don't test a new one in your warm house and then go out and test one in your cold car. Test then in the same conditions.

Stuart

Ok Stuart, I'll do some research. Just out of interest if you're travelling at a constant speed i.e A roads or motor the temp get cooler, does this mean the outside flaps are staying open allowing outside air to be filtered into the cabin?

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Stu ..

I've had my clocks out a couple of times but haven't seen the sensor anywhere in the vent - can they drop down?

Greggers - The vent sensor is on a wire directly behind the central vent. It should be visible when the plastic surround is removed. It should also be visible with surround still attached as long as the vent is open. It may have fallen in your case, think it clips onto something but is essentially in the airstream that blows into the cabin.

Rajg - The HVAC will open and close flaps according to temps and requested temp from the heater control. If the thermistors are out of spec you will experience what you are experiencing.

Stuart