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

I was told by Williams that the reason the heater control is so much stiffer to turn than the fan switch is precisely as you say, Richard. It is turning a valve. My Plus 4 heater control has 5 positions, from Off, to Very Hot!

thanks for all your comments.

I wasn't paying particular attention to the temperature gauge on the run although it might have been showing a bit cool - round about the 80 degrees mark.

The heater knob seems to have just 2 positions with an 1/8th turn difference. It doesn't click (by feel or sound) like an electrical switch but it's a very small movement for a bowden cable. I'm thinking of choke & magneto controls on old motorbikes.

The dealer thinks it is the thermostat but gave the impression that it isn't a familiar problem.

So it's time to take another run to check the heater hoses then drop the dashboard to have a look at the heater control.

Check the engine top hose at the same time to rule out or confirm a thermostat problem.

If the top hose is hot but the heater hose is coolish then the problem is somewhere in the heater circuit but if both hoses are coolish I'd be looking at the engine cooling system for example the thermostat.

If the thermostat and engine cooling system are working properly the engine should get up over 90 deg relatively quickly even in cool weather and stay there.

SORTED!
There's no such thing as a problem - it's just another reason to go for a run. Took the Mog for a run round the Mendips to warm it up.
1 when the engine's warm the gauge shows 95 degrees
2 back home both hoses are too hot to grasp
3 time to look behind the dash. Three screws on the front but a number of little black ones holding the fibreboard cover underneath the dash then...
4 While looking for these noticed that the louvres on the driver's side are in fact closed... (back to 3)
3 (cont'd) with the dash off it begins to make sense
- the heater control uses a bowden cable and has 2 quadrants - one with 6 holes & the other with a sprung ball for control
- turning the control shows lots of movement and 4 clicks (cable's too tight to reach the last detent)

So the problem was that the back of the control was fouling something out of sight behind the dash.

Put it all together last night taking care that the heater control has full movement. Then this afternoon just had to go for another run to prove it all worked in the real world. Hooray!

Glad you got a result

Pictures below illustrate your findings. Although from Roadster's, it sounds like the mechanism is shared with other models.



The toothed wheel immediately behind heater control knob engages with holes in outer quadrant of pivoting lever shown below. The stepped end of inner part of bowden cable is clipped into hole on lever to transmit movement to heater control valve.



I guess the holes of inner quadrant are supposed to engage with spring ball detent. Not seemingly on mine though

Useful pictures! I think I almost understand it...

Heath Robinson would be proud that one of his designs is fitted to the Morgan