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Overheat / cooling fans failure? ... how to check


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I suspect a cooling fans issue on my S2.
When I'm driving on empty roads outside the town, the TEMPerature indicator barely gets over 90 degs.
But once I'm in the traffic, it raises up to 115!
I checked that there is still coolant in the header tank. I don't think the problem is at this level.
So I checked the cooling fans, located on the front of the car. There are three fans close to the radiator :

lotusfan1.jpg

 

Here's my question, when you start the car, do these fans start immediately to turn? Or they wait a signal starting a certain temperature before starting to work? Like if temperature reaches 70 degs, start the fans?

I've seen a similar topic...

...and I would like to check if it's maybe just a fuse or wire problem. But, I can't identify what is the fuse to check :(
Which one is responsible for these fans to run? See ->

lotusfan2.jpg

One of the big fuse is labelled "heat fan", but I'm looking for the 'cooling fan'. Can you point it for me please?
Thx for your help.

 

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Find the temperature switch ("otter" switch in Lotusspeak) that turns the fans on. On an '82 turbo, it lives in the radiator hose on the RHS of the car, in front of the front RH wheel. Remove the two connections from it...then connect them together with a piece of wire. Once they are connected, with the ignition ON, the fans should start. If they do, then the fans are OK....and  the failure is probably the "otter" switch. You can check the switch by removing it from the car...in my case, it is held in by a simple chromed steel clip fitted under the rubber seal to the pipe, unclip to release the switch (with the engine cold!!) then, with a suitable cork or stopper to hand, pull out the switch and poke the stopper in the hole before all your coolant ends up on the floor. A container for this helps...(!) Once you have the switch out, go to the kitchen and get a scrap saucepan and put enough water in it to cover the switch. Connect a test meter set to "ohms" across the switch and heat the water until it boils. The meter should indicate the switch operating (ohms reading drops to near zero) once the water temperature gets to about 82°C; if it does so by the time the water has boiled, it is probably all right. The switch operates a relay which operates the fans. This relay has a fuse fitted to it...the "fan fail" fuse. If the fans fail, then the fuse will blow and the "fan fail" warning light will come on. Once you know what is actually happening, then you can find out why and what to do about it!! The "Servicing Notes" have the wiring diagrams and component layout, and are indispensible for owners wqanting to understand what's going on....

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Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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One additional bit to John's information. If the earth wire for the fused relay becomes disconnected, the fan fail light also lights up and the fans don't start. The earth wire may not be directly connected to earth. Mine went via the washer bottle motor. This happened to me at the beginning of May.

 

 

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The otter switch in an S2 is in the engine bay. It is wired into the aluminium S shaped pipe to the right hand front corner of the engine bay. Do as John says and connect the terminals together. If the fans start than you have a faulty otter switch which is simple to replace. You may find that the terminals of the switch have corroded or the wires are not connected properly.

Your fuse panel is not standard, neither are your relays so there's no way of telling which is which unless the person that installed them has a diagram.

Next step is to turn the fans by hand and see if they rotate easily. They do seize up over time and will blow fuses when they do.

Pete

Pete '79 S2

LEW Miss September 2009

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Thanks guys for your fast answers.

Just checked the 'Lotus Esprit S1/S2/S2.2' workshop manual for more details about the 'Otter switch', and found this diagram :otto1.jpg

 

...which doesn't really help, because on it, the Otter switch is supposed to be located at '9' ?

But on my car, I guess I can spot it somewhere else? ->

otto2.jpg

So I guess it's the famous 'otter switch' ->

otto3.jpg

So as you suggested I guess I can remove it and check the connectivity? And 'bridge' (= to bypass the otter switch) the connectors to see if the fans works at ignition of the car? 

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There is of course an easier way to check the fans, just run the engine up to the 115 deg temp which you are seeing and have a look at the fans!

Its possible they are working. In fact if the engine temp stabilises at that value and doesnt go higher, it is likely the fans are coming on. A gauge reading of 115 is not unusual, the gauges are not very accurate and when stationary in traffic the water circulation is not great so even if the fans are running the temp does run high but drops when revs are increased. 

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That's it. You can leave the wire on just to pull the leads off, don't take the switch out of the pipe yet. On mine the leads attach individually, they are not connected to a plug.

Andy is right, you could leave the engine running and see if the fans kick in but whilst you have access to the otter switch you might as well try bypassing it. Quicker and less noisy option...

Your header tank is also not original and in a slightly different place which maybe why your engine bay doesn't match the picture in the manual.

Pete '79 S2

LEW Miss September 2009

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Problem 'half solved'... I noticed a 'custom' switch on the dashboard :

custom.jpg

...and yes... that one activates... the fans!
At least I can face traffic jam with no stress! I tested it, and temp won't go over 95 deg when fans activated in slow traffic. B-)

On 27/6/2016 at 11:59, peteyg said:

Your fuse panel is not standard, neither are your relays so there's no way of telling which is which unless the person that installed them has a diagram.

 

 Hi Pete, do you a picture that shows a 'standard' fuse panel /relays on a S2? Because stuff on mine, if not standard, it looks pretty legit and very well done, no?

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The job looks serious, you might be better off that electrical installation than the original:P

Something I learned about cars or planes, it all works until it doesn't anymore...sometime there is no way around it!

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I would say Luc is right. If you're not worried about originality then keep what you have. It looks much more substantial then the original which is 8 fuses in the glove box. I have added extra relays because the original setup was not good enough.

Pete

Pete '79 S2

LEW Miss September 2009

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On ‎6‎/‎27‎/‎2016 at 08:37, jcslocum said:

On my '84 Turbo the Otter switch is in the tube that goes to the thermostat housing:

 

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Follow the arrow :-)

 

82434ba1-e2a0-4066-a1a6-c033f0381d34_zps

 

@jcslocumJon, slight thread highjack, but how long did it take you to remove the carbs on your car?  Big pain in the a** or just a slow process?

Edited by Geeman
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