Disco II (99) heater blows cold

[madprofessor]

1999 Disco II blows cold air no matter how high the temperature is set, even when engine is well warmed. Same in ECON mode.
Manual ATC ECU diagnostic test indicates no faults.
I am thinking it can only be a stuck or malfunctioning heater matrix flap or clogged heater matrix (unlikely). Any suggestions?

[Mantamad]

I am just thinking aloud here but would guess that as the heater control is via the electronic panel, the actual valve that regulates the flow of water through the heater matrix must be an electrical type - its possible that this could have seized or the connection to it is faulty.

[Brucey]

Sorry if I'm stating the obvious, but have you checked:
That there is sufficient water in the radiator? I have had a 4wd that held the water in the header tank without dropping it into the radiator!
Check for an airlock in the heater hoses
Does the thermostat close, i.e.does the engine warm up properly? (Doh, you said when hot, delete that!)

Just thoughts.

[vitalspark]

Is it A/C fitted with `climate` etc. These are complex bits of kit. I have this in mine, although all works ok, touching wood, but there are blend valves and all sorts of electronically controlled adjustments that happen automatically. Try dropping the desired temp by 1deg. and a few seconds later flaps click and motors blow etc. However, I would have thought that if there was a motor or flap fault it would only affect one side. If nothing at all then perhaps a power supply problem to wherever the ecu for the heater is, I`m only guessing, but when something is totally dead its usually back at source rather than a component within, also usually easier to trace when complete failure.
Sorry no help, let us know the outcome.

Dave

[Hightower]

I had this problem on my Disco a couple of times.

Check your coolant level. First time the rad was leaking, the next was a blown head gasket. Both led to coolant loss and a severe lack of heat . . . . .:icecube: