Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 4/4 heater not heating

I can't find a thread that covers my question so here's a new one.
I bought my 2013 4/4 this year and love it (mostly).

Yesterday (mid October) I had a run up to Stafford. I reassured myself that the heater would warm me up soon but 2 hours later felt that something was not quite right. Fiddling with the blower - Off/Slow/Quick - and heater knob - Off/On - made no difference. Then, queuing to get into the show ground, the auxiliary fan kicked in although the outside temperature was barely 10 degrees. And the heater started blowing HOT air. Sadly the change didn't stick around for the return journey.
So what's wrong? The last car I seriously tinkered with was a Morris Minor 40 years so after checking the fuses I've stopped to seek advice.
I'd like to get it sorted as I don't intend to 'winterise' my Mog soon. I'm enjoying it too much.

There are two things I would check first...…..that hot water is flowing through the heater.....by feeling the inlet and outlet hose.....because there could be an airlock. As the engine warms, you will feel which is the iinlet hose.….

Also check the cable behind the dash, that the heater knob is moving the cable properly....you can easily drop the dashboard forwards....either three of four screws hold it in place.

Drop the steering column to its lowest point before you do this.

Stafford yesterday, must be the Classic Bike Show. I missed it this year.

Question for you, did the engine temperature gauge show normal warm on the journey up.

Just thinking as I had a similar problem on my Zetec engine car in the early days and that was because the engine coolant was not getting up to temperature because the thermostat was stuck open giving a constant cooling effect from the radiator rather than being controlled by the thermostat. More noticeable on cold days.

I sorted the thermostat and the heater started to work as well.

The problem is that the later Zetecs and maybe your Sigma engine don't actually measure water temperature but have a sensor in the engine block or head so it could show a warm engine even if the coolant was still not up to temperature

The reason it was hot when you were queuing could be that, as the radiator had no air flow, the coolant and hence the heater would get hot.

Just a thought.

If there was no flow through the heater or the cable was not moving, why would it get hot standing in traffic?

All worth checking though.

Are the vents under the dash open?

Because the cooling fan will blow hot engine air into the cockpit if the seal isn't good.....

Also the heater control knob is fairly stiff and from zero to full on should turn about 5 clicks.

isn't it the case with the 4/4 that the temperature control is only a wire rope hoist? and this wire rope hoist opens or closes a flap to allow hot air to flow in? In other words, the heater is almost always "on" in the sense that hot water is always present but it is only "switched on" respectively used when the hot air flap is open?

Do what I do empty the system including a hose flush it out . Then fill it slowly ( INC ANTI FREEZE ) get it 1/2 TO 3/4 full and let the engine run a short while and grip each hose . Should feel almost the same !. If so top it up and give it a run . Watch out for the hot water when you take off the rad cap if all is OK .
PS .I put silicone hoses on a few years ago

Surprised if the Bowden cable doesn't operate a remote mechanical valve controlling water flow through heater matrix. Apparently this system can be badly adjusted though, to leave a residual flow of water through heater when set to fully cool.

On my Roadster the control is certainly stiff enough to suggest this, no intermediate click positions either.