Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing ‘97 PLus 8 fan will not does not stop

Hello Morgan fellows,

I got my 1997 Plus 8 back from MoT test today and find that the fan will not stop running. The garage boss says they did not adjust or otherwise interfere with the fan mechanism (no need to in course of the MoT procedure).

My questions are: whether it is harmful to have the fan running non-stop. It will stop when the engine cut-off switch is applied but runs constantly while driving.

And, what are the possible causes and remedies?

Any suggestions, advice, help greatly appreciated.

Cheers Nick Welch

Back in May I think it was my Plus 8 was in for MOT and I had given it a bit of welly on way in to the testing station, it was a very hot day and as she was being checked for emissions she spat fluid out of the overflow from the bulkhead header tank and the fan just carried on running for the duration of the test.
Normally it would be cycling.

Once she was outside again and cooled down a bit she was topped up with around a Litre of water/antifreeze by the engineer and the fan has operated correctly ever since.

p.s. If it does not stop in the cooler weather it would overcool the engine which is never a good idea for obvious reasons.

As Richard suggests check if the rad cooling fan comes on when ignition first switched on and cold engine, bearing in mind we are suffering very warm weather. If it does suspect the fan relay or otter switch which triggers it on coolant temperature.

If fan does come on with cold engine and ignition on, check first the otter switch by disconnection, if fan stops you have faulty switch. Unlikely the fan relay would have failed in the on position but short to ground in its trigger wiring would be possible. Assuming its a plug in one a quick check is replacement with new matching relay.

Thanks Rich and Richard,

It has been hot in Sussex so maybe that is the explanation. Still, the only way to stop the fan is by engaging the general cut-off switch (red/orange plastic lever between the rear footwells) and vice - versa - fan comes on immediately cut off is disengaged. Never heard of the ‘otter switch’ - but I am grateful for that information to pass to the garage. And for the suggestion re fan relay. We’ll see!

AI response on otter switch query.

An otter switch is a small, heat-sensitive bi-metallic electrical switch used in classic cars (like vintage Jaguars and Lotus models) to turn on cooling fans or control automatic chokes when the engine gets warm. It got its name from the manufacturer, Otter Controls, a British company founded in Buxton, UK, in 1946.

I think the original had heavy enough contacts to directly switch cooling fan motor. Relays were added later but the generic name stuck.

Nick,

As the fault only appeared post MOT I would be inclined to think they inadvertently disturbed some part of the cooling system or possibly the otter has taken a dive but this is readily disconnected or by passed to check it's function - I removed mine on my first car and checked it's operation out, suspended but with lower section lmmersed in water in one of the long haired Major's saucepans. You have to chose the right moment of course..

Ohmeter and her jam thermometer is all you need.

Thanks again both for the further suggestions. I have now passed the problem to my local morgan-eer to be looked into while in for its annual service (not wishing to incur the wrath her in the kitchen with that immersion idea!). Cheers, N.

Please let us know the outcome Nick.