05 Avensis Heater

[datsun100a]

apologies if this has been asked before

My heater seems to have a mind of it's own these last few days, climate control type. It produces very little heat in the mornings but seems fine later in the day. I have checked water levels and for air locks etc and the engine is heating up fine, top hose is hot.. I suspect it could be a servo valve that is operated by the heater system to adjust the level of hot water entering the matrix. If the matrix was faulty I would think the problem would be there all the time.

any help would be great...

[Jamesbelfast]

With heater motor blower switched off and the engine hot both the pipe going into and the one coming from the heater should about the same temp. The matrix will only lose substantial amounts of heat when air is being forced through it. Very few modern car heating systems have coolant control valves but have a flap or blind which exposes more of less of the matrix surface depending on the heat settings Also most climate control systems will have a cabin sensor which monitors cabin temp, humidity and oxygen levels. For all these controls to operate correctly it is necessary for the heater system to have an clean uniterrupted air supply so it may be prudent to have a look at the condition of the cabin/pollen filter.:)

[datsun100a]

With heater motor blower switched off and the engine hot both the pipe going into and the one coming from the heater should about the same temp. The matrix will only lose substantial amounts of heat when air is being forced through it. Very few modern car heating systems have coolant control valves but have a flap or blind which exposes more of less of the matrix surface depending on the heat settings Also most climate control systems will have a cabin sensor which monitors cabin temp, humidity and oxygen levels. For all these controls to operate correctly it is necessary for the heater system to have an clean uniterrupted air supply so it may be prudent to have a look at the condition of the cabin/pollen filter.:)

cheers for that, i'll just get a new filter then as the old one is about 2 years old.Worth a try first.

[datsun100a]

Worked a treat renewing the filter. amazing how dirty it gets so I need to replace it every year.

Thanks for the advice.