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MC07GAN

Heater Control Panel Not Working ? 2004 Avensis S D4D

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Hi,

For the last 2 - 3 years I have lived with a single blown dash bulb situated behind my manual 3 dial heater controls 2004 D4D Avensis.

I found some instructions to fix it yourself and also replaced all 4 bulbs in the unit (3 black and 1 grey which I got from Mr T = £26)

All was put back in place and when I tested (new bulbs and fan) everything seemed to be working correctly.

It wasnt until the first frosty morning did I realise that although the fan was making all the correct noises there was no great heat coming from the heater or the heat direction dial was making any difference when turned.

The car does get slightly warm up after about 15 min driving but it stays at a tepid temp which is not enough for example on a cold morning. Even when the car has warmed, altering the heat and direction dials does not seem to make any difference what so ever.

Radator seems fine not losing water. Warm at both rad pipes when car is warm.

Doesnt seem airlocked. Squeezed rad pipes with engine running and rad cap off.

Pretty sure not head gasket. Not blowing hot then cold inside but remains at a constant tepid heat when engine has warmed. Engine not overheating. No massive eruption or pressure build up when taking the rad cap off and just seems normal pressure. No water loss.

I took the heater control out again to see if there was anything obvious but all seemed correct in place. I also plugged the heater control back in on its own so I could push and play with the conecters in case there was anything loose but no change.

Does the heater control unit have a fuse ?? I checked the fuses but couldnt locate one.

At the back of the heater unit there are 2 power plugs that connect. The first plug controls to the fan speed

that seems to be working fine and the second plug seems to be the suspect as I guess this must control the

heat and direction dial ?

If not a fuse I am going to order a new heater unit.

Thank you for any advise.

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Hi,

For the last 2 - 3 years I have lived with a single blown dash bulb situated behind my manual 3 dial heater controls 2004 D4D Avensis.

I found some instructions to fix it yourself and also replaced all 4 bulbs in the unit (3 black and 1 grey which I got from Mr T = £26)

All was put back in place and when I tested (new bulbs and fan) everything seemed to be working correctly.

It wasnt until the first frosty morning did I realise that although the fan was making all the correct noises there was no great heat coming from the heater or the heat direction dial was making any difference when turned.

The car does get slightly warm up after about 15 min driving but it stays at a tepid temp which is not enough for example on a cold morning. Even when the car has warmed, altering the heat and direction dials does not seem to make any difference what so ever.

Radator seems fine not losing water. Warm at both rad pipes when car is warm.

Doesnt seem airlocked. Squeezed rad pipes with engine running and rad cap off.

Pretty sure not head gasket. Not blowing hot then cold inside but remains at a constant tepid heat when engine has warmed. Engine not overheating. No massive eruption or pressure build up when taking the rad cap off and just seems normal pressure. No water loss.

I took the heater control out again to see if there was anything obvious but all seemed correct in place. I also plugged the heater control back in on its own so I could push and play with the conecters in case there was anything loose but no change.

Does the heater control unit have a fuse ?? I checked the fuses but couldnt locate one.

At the back of the heater unit there are 2 power plugs that connect. The first plug controls to the fan speed

that seems to be working fine and the second plug seems to be the suspect as I guess this must control the

heat and direction dial ?

If not a fuse I am going to order a new heater unit.

Thank you for any advise.

Did you fix this problem as my car has the same problem

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Most common advice to owners with these diesel engines who are having trouble with their heaters is to get the cylinder head gasket checked out "sniff tested" to chekc for combustion products eg CO in the water.

That apart, there seems to be ongoing issues with the heaters on these and the Corolla Verso. I've seen a number of posts about ppl suspecting their water pump, citing worn impellers giving poor flow and of course the thermostat is always a candidate. Is the heater matrix on these cars sited very low down so there's no assist to the flow? Or is there so much water diverted through other components eg the EGR valve that flow to the heater is marginal at best and easily disrupted?

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Not seen a headgasket issue for the 2004 diesel yet. The ad engine series have the head gasket problem which is 2005 for 2.2 2006 for 2.0

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