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Cooling Fan's Not Working
could it be the OTTER Switch?

Our Turbo overheated in a traffic jam on a hot day. We had some steam coming out of the engine bay and had to pull over. On investigation we found it was just overheating due to the fans not working. Once the Esprit had cooled we could continue on our journey without any damage to the car.

Giugiaro overheating problem is normally the OTTO switch. This is a thermostat switch that controls the fans with water temp. It changed location during manufacturing, it's either in the aluminum tube which connects to the top hose of the engine or the aluminum tube that links the top hose to radiator which is difficult to access, (parts manual section 46).

If they don't work it's normally the fans but it could be other wiring problems and you will have to test each fan with direct pos and neg power supply. If Otto switch is ok, another cause could be dirt/debris in the fins of the radiator blocking air flow.

This is a guide on how to check the operation of the Otter switch and making sure your fans are working correctly.

Early Turbo models, S3 cars with air conditioning, and Series 3 cars with heater prior to commonisation with Turbo fascia (mid '85) used a fused relay in the cooling fan circuit located at the left hand front of the front luggage compartment. Later cars were fitted with a revised circuit to incorporate a double pole relay and a modular three pole thermal circuit breaker with manual reset . On these cars , an excess current in any one or more motors will cause its own thermal circuit breaker to operate. If any thermal trip is open, or any motor fails to rotate at an effective speed, an earth path or voltage difference is created and the fan failure tell tale will light . Pressing down the red reset button on the trip housing (adjacent to windscreen washer reservoir ) will restore any tripped circuit .


Cooling Fans Thermal Switch
The cooling fans thermal switch (sometimes referred to by its manufacturers name, 'Otter' ) is fitted in to a waterpipe between the thermostat outlet and radiator inlet , using a special grommet and spring clip . Never re-use a grommet, but renew each time the switch is removed.

Cars used in hot climates a refitted with a blue colour coded switch which makes/breaks at temperatures of 82/7Z°C. The switching point for cars in temperate climates was raised from 86/76 t o the 92/82 of the current green colour coded switch.

On DOM/ROW Turbo models the switch is fitted in the radiator inlet elbow pipe. Until Dec. '84, the pipe was fitted with the switch pointing upwards but the possibility of an air pocket being trapped around the switch and the consequent erroneus temperature sensing, led to the pipe and switch being inverted .

Removing & Replacment or Cleaning

This job will take about 1.5 hours and isn't particularly difficult.


You will need the following parts:

New Otter Switch
New connectors

You will need the following tools:

Wire cutter/stripper
Jack + Axel Stand


First thing to do is jack the Esprit up and get the front right wheel off to gain access to the Otter switch. Remember to use an axel stand for safety. You can see the switch easily once the wheel is off. Our switch was upright, which makes working on it much easier.


We did this job on the hop! So didn't replace any of the parts. This was done just to get the fans working. The parts will be replaced later. When we tried to pull off the wires, the connection just crumbled in our fingers. That's probably why the fan's weren't working! We removed the switch to clean up. A previous owner had use some wire to make the switch more secure, this was cut and the switch pull out. You'll start to lose some fluid, so use some rags to stop the flow.


You can see the corrosion on the connectors from this shot on the right. We stripped the wires and added new connectors.


Time to test the connection before putting everything back together. To do this touch the two wires together with the ignition on. This should set the fans off. Make sure you've nothing fowling the fans and your fingers aren't too close. If you're still using the original connectors, you'll need something like a paperclip to touch the connectors together with, as they are in a plastic covering.

Some fans run ON with ignition OFF when water temp is high, but test with ignition ON then you are sure.

(note: I think it would be helpful to mention that one should feel air blowing towards the back of car when testing the fans. I have seen cars with heating problem because fans blew in the wrong direction. Believe it or not, it is most noticeable when driving on the highway because that's when it would overheat. Rich Flowers)


Once you know the fans are spinning ok and the Otter switch is the problem, you can clean up the switch or replace it. Then its time to put everything back together.


Place the switch back into the grommet, which you should replace, but can get away with re-using short-term. The switch should easily push back into the pipe. You may want to secure it further by using some wire around the pipe. Remember the pipe gets very hot, so no plastic cable ties!. Reconnect the wires and you're good to go. We grease up our connections, as we now had no plastic covers. This is worth doing anyway, as it will help protect the switch from all the dirt and debis from the road. To test, take the car on a run to warm the system up. Then leave running to make sure the fan cut in.


These pictures were sent in by Darrin Alker who has also done this work. He's switch is inverted as shown in the illustration above. His pictures show how wire can be used to support the switch to make sure it stays where it should. The middle picture shows it wrapped up in tape to protect the connections from the elements. Lastly the piece that make up this piece of the car.

LEW's Verdict

This will probably happen to most Esprits with an Otter switch situated here, as the wheel throws up plenty of dirt and debris. Keeping an Esprit cool is one of the more difficult things, with a small nose and an engine in the middle. Making sure the fans are working, especially if you're driving in the summer is critical for the cars well being. We would advise checking the fans are working regularly. So when you get stuck in that traffic jam, you don't overheat.

As for actually doing the repair, it's very easy. New parts would be advisable if you've planned the work. Otherwise cleaning them up is ok short-term. This only takes a couple of ours and only a few tools are needed. Even somebody with limited experience on working on their Esprits should be able to carry out this work.

This mod was performed by LEW on their 1984 Turbo Esprit

If you have any comments, feel free to e-mail me with at admin@lotusespritworld.com

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