Seat Alhambra Heaters problem

[Abdulghafoor]

Hi, I have seat Alhambra 2006 2litre TDi. I have an issue with heaters. When car starts, the rear heater is always working but the front heaters are barely warm. when I rev the car they start blowing hot air. but soon after driving a mile or so the air from only front heaters goes cold again. I have changed thermostat, water pump and even expansion cap. Car never overheat and no other warning signs. Plz help

[brianh]

Does your run on pump (located on the bulkhead next to expansion tank) work? You should be able to hear it/feel it running for a few minutes after you shut the engine off, if you can't then it probably wants a new set of brushes installing, there are instructions on doing so on the site here.

[johnnyroper]

Hi, I have seat Alhambra 2006 2litre TDi. I have an issue with heaters. When car starts, the rear heater is always working but the front heaters are barely warm. when I rev the car they start blowing hot air. but soon after driving a mile or so the air from only front heaters goes cold again. I have changed thermostat, water pump and even expansion cap. Car never overheat and no other warning signs. Plz help

What does temp gauge read does it drop when at idle of is it steady at half way point?
The run on pump assists with the coolant circulation however when mine was duff it was rear heater that suffered the front heater remained hot.
I know you said thermostat been changed but donââ,¬â,,¢t rule out new one is faulty as you have classic failed stat symptoms. If you warm car up on idle does the hose from thermostat to rad get warm as car warms up? Try clamping thermostat outlet hose as a temp measure to see if heater remains warm.
What brand of thermostat did it have fitted? I had an x type that run cold I replaced stat with circoli one but it made no difference once I replaced again with OE it was fine.

[christiant]

It's worth looking at the aux heater as well, because if it is cold enough it is possible that is the cause. Mine does the same at temps under 5C due to the aux heather not working. You can just check the hose coming out of the stat housing right before the engine reaches 90c and the hose should be slightly cooler than the ones running around the other side of the head. If so your thermostat is probably fine.

[Abdulghafoor]

Hi, thank you very much for your kind replies, The temperature gauge does not drop or exceed 90.

[brianh]

If the aux heater is working, and the rear heater is working ok, that suggests the problem is at the front, if the coolant hoses leading into the front matrix are both hot then it suggests either the flaps inside the heater box aren't correct, or the matrix is blocked up and not getting enough coolant through it. What state is the coolant in? Does it look like clear coloured water or more like liquid rust?

[Abdulghafoor]

Hi, It is clear no rust or any other colour. The front heaters work if I rev the car but as soon as I stop on traffic they goes cold again. But the rear heaters remain hot all the time as normal as they should be. If its matrix then what should I do, do i have to open whole dashboard?

[johnnyroper]

As the rear heater remains hot even on idle that suggests the cooling system is functioning as it should and the problem lies with the front heater matrix.
To remove the matrix it is a fairly big job involving dash removal.

Might be worth trying to flush it out first by removing hoses and back flushing with a hose pipe. To be getting hot when engine rpm up but cooling off on idle I would think some of the cores are restricted.

[Abdulghafoor]

Thank you, I nearly gave up and was thinking to book it with dealer but will check this option now.

[Abdulghafoor]

Plz guide me about cores how do I check these  many thanks

[johnnyroper]

Donââ,¬â,,¢t think you can really check on a heater matrix as you cannot feel for cool spots like on a radiator. Flushing through with hose pipe will show the flow through it to a certain extent.

[brianh]

Donââ,¬â,,¢t think you can really check on a heater matrix as you cannot feel for cool spots like on a radiator. Flushing through with hose pipe will show the flow through it to a certain extent.

I've had a heater matrix out, and yes there isn't a way of checking as to get it to a point you can touch the core you need to remove it, at which point its not plumbed into the coolant so you have no way to tell. Its not as bad as you expect to remove the dashboard as long as you have a second person to help you get the dashboard out once its loose. Replacing the heater core after that isn't too major, just a slight pain to get the old one out/new one in if you don't want to take the heater box itself out, though that can be worked around by having a long phillips head screwdriver to poke through the bulkhead to do the screws up on the pipes, and minor cutting of some of the retaining plastic (its designed to be put in the heater box then the box installed into the car, least the mk1 was like that, so without unbolting the box it won't go straight in, but its possible to get round that, ideally you don't want to disturb the a/c if its working, which moving the box would do).

Hosepipe option is best bet as first call - disconnect both of the hoses that run through the bulkhead so you have both sides clear, flush it though on both for a few minutes (do both sides so anything that can come loose to either side will do - might even be worth repeating it a couple of times on each side depending what comes out). If your really lucky it may just be blocked, but be prepared if someone previously has "repaired" a leaking matrix with radweld that it may start leaking again. Also have a check that none of the hoses down the front of the bulkhead are kinked or restricted in anyway if someone has had them off previously and not got them back on correctly this might be possible, and would cause the same sort of problem.

Do you get any coolant loss, or can you smell a sickly sweet smell from the front heater area, or get excessive misting up of the front screen when the heater is set to hot?

[Abdulghafoor]

Thank you so much for such a detailed reply. And no, there isn't any smell or stickiness at all

[brianh]

I'd risk giving it a flush out personally then, of course the smell is only going to be noticed if theres any antifreeze in the coolant system, but as long as your not finding the misting issue you should be ok. Worst case you will have to replace the matrix, which is doable without too much hassle provided you have the correct matrix to fit.

[johnnyroper]

When I did mine I managed to remove the bolts holding heater box in and lever it away from bulkhead enough to extract it and get the new one in. If I remember cocctectly the pipes on top of new one were removable which made it a lot easier as I could put matrix in then the pipes on top and through bulkhead. Just had some o rings on them and secured with Phillips screws.

[brianh]

When I did mine I managed to remove the bolts holding heater box in and lever it away from bulkhead enough to extract it and get the new one in. If I remember cocctectly the pipes on top of new one were removable which made it a lot easier as I could put matrix in then the pipes on top and through bulkhead. Just had some o rings on them and secured with Phillips screws.

I seem to remember having to remove some of the plastic ontop of the heater box on mine, but yes similar. Thats the bit you want the long screwdriver for (put it through the foam bit that goes through bulkhead to do the screws up on the bits of solid plastic pipe to attach to the matrix) Old one not a major problem at that point as long as your happy the replacement is the right one breaking it to get it out not a major concern. But hopefully the OP doesn't need to go that far.