Xantia heater not working cold air flaps/blower

[Stickyfinger]

Ahhh.....they go in vertical do they ?

Yes, heater hoses both get hot.

[peter306]

They do.
Just read the posts again, if both hoses are getting hot and you reckon you had a good flow through then i would let the car get cold, with the heater fan turned of (no air over the matrix) see how quickly the outlet hose gets as hot as the inlet hose, if it's quickly then i would suggest the problem isn't the matrix.
The bit where it gets warmer then cools, could that be the thermostat kicking in.

[Stickyfinger]

Yes, both matrix hoses heat up quickly, they get to temp before the stat opens.......BUT

As soon as I put the cabin/heater fan on I feel heat, quite hot, then this heat output rapidly decreases to luke warm............

The car maintains 80 on the gauge when driving, the fans kick in at 90 when idle......I tested the stat, it opens correctly in hot water.

Heater cable open/close the hot air flap correctly, operation shuts/opens & allows warm air/cold air to be selected.

[peter306]

Seems to me the matrix is working ok.
there is a post on here about the cabin temp sensor, behind the little grill above and to the right of the radio, if its little fan isn't working it gets heat from the radio and it thinks the cabin is too warm. There are also a couple of other sensors, one is in the inlet just after the pollen filter, another is behind the ash tray, they are probes and the one behind the ashtray may affect cabin temps, don't know what the parameters are for them.
I think we need Jim.
Peter

[Stickyfinger]

Zero sensors, this is a 1993 car, no Aircon, no "auto" air/fan etc... bare bones

[peter306]

Bit lost then.
Does it do the same on recirculated air.
As it's all manual the only other thing I can think of is that the pipes in the matrix are narrowed so there is not enough heat reaching the outer surface of the pipes to overcome the cooling effect of the air.I've used the Forte cleaner and degreaser to good effect as on the forum there are comments to only use this in the heater matrix.
Peter

[Stickyfinger]

that the pipes in the matrix are narrowed so there is not enough heat reaching the outer surface of the pipes to overcome the cooling effect of the air.

Yes, sadly that is now the only thing I can think of as well. I used FERNOX system cleaner, designed for scaled heating systems and this did not work.. My reasoning for the failure is that the surface area acted on is so small (just the end in the tube) that chemicals will not work.

Planning to replace the matrix in the summer months.

Cheers

Alasdair

[CitroJim]

I think we need Jim.

Yep, I'm already all over it like a rash Peter Alasdair and I have discussed it at great length and last week we both tried a few good bleeds after the Fernox to reach the conclusion you have now confirmed

I'll be there to help replace the matrix... I've done so many in the past I can almost do then in my sleep and Alasdair's, being an early non-aircon, will make the job a bit easier...

We did once ponder if a mouse had bult a nest in the heater box but the airflow does not support that line of thinking and there's no stink.

[peter306]

If you have a third hand then run it up to temperature with no airflow, whop the slider over to max and feel if the outlet pipe gets colder, that would about confirm it.
See, I knew we needed Jim
Peter