what is the problem when your car heater is not working is it the thermostat ther is plenty of water in the radiator ther is no leek and it is blowing out cold air

peter stewart, October 2007

hi I have a fiatpunto 1.2 active 57 plate , I turned my heater on in the car and it wont blow hot or cold just nothing don't no what it is

shelley, December 2013

HEATER NOT BLOWING HOT OR COLD AIR OUT

ROBERT WASTELL, March 2009

heater was blowing cold.went through usual checks.there was no change in the sound of heater when switched between hot and cold.the cable had come off the flap that regulates the temp.this is located under dash on drivers side

andrew ov bacup, February 2009

add a rad cleaner leave for a few days then drain.then undo the to hose pipes that go to your matrix put hose pipeinto one pipeflush through if water dos not come though suck and blow till water flows reconect all pipes you will have heat

bob t, January 2009

Hi there, I have a prblem where my fan for my heater is just not switching on. I can feel the air is warm, but the fan will not come on. anyone any ideas? Ive checked the fuses which seem to relate to the fan, but i wasnt sure...apart from the fuse...anyone got any ideas what would cause the fan to suddenly stop??

sandy, October 2008

Hi first off, if heater blows cold air whether driving or standing still, probable causes are
1. it's not the thermostat, reason - hot water flows through the heater matrix from the cylinder block so the heater will still work, how hot depends whether thermostat is open or closed. Considering everything else is ok.
2. blocked heater matrix hot water cannot flow through heater matrix so blows cold air, very expensive to repair but depends on how heater matrix has to be removed. Check both inlet and outlet pipes of heater matrix if hot see (3)
3. Water is not flowing through heater matrix because of insufficient force. Water heats up through engine running, thermostat opens letting hot water out of engine and into radiator, water flows through simple physics ie hot water rises and pushes cold water out of radiator and into engine. Eventually thermostat remains open and then cooling fan starts cooling water in radiator so engine does not overheat.
Sometimes heater starts to blow warm air when standing still and engine is revved but goes cold when engine returns to idle or does not get warm at all, reason - water pump is knackered and is cheaper to replace than heater matrix, if heater is still cold replace heater matrix

Ken Roper, December 2007

If it has just gone like this it's unlikely the heater is blocked.
Did you have to put any water in? There may be an air lock. Warm the engine then open the bleed screw in the hose to let any air out and wait for water to come out, then close it.Top up coolant reservoir again and see if that makes a difference.
Check the heater hoses to see if they are nice and hot.
If they are then next check the hot/cold control works.
Turn the heater on full and you should hear a difference in the air flow as you switch from cold to hot.
Once the engine has warmed up, the heater should still get warm even if the thermostat has stuck open. It just takes longer for it to get hot.
If your'e not sure, get a garage to take a look.

Tbird, October 2007