Engine Fans: Low works normal but high never comes on - LotusTalk - The Lotus Cars Community
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post #1 of 12 (permalink) Old 04-10-2014, 03:49 PM Thread Starter
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Question Engine Fans: Low works normal but high never comes on

I have searched for something realatively close to this, but haven't had any luck. So, the car (2005 Lotus Elise, sport and touring pack, with a/c) I am looking at has some a/c issues which seem to be caused by engine fan opperation. From what I can tell there is 4 opperations for the dual engine fans.

1) Cold engine with a/c off, fans off
2) Cold engine with a/c on, fans operate on high
3) Hot engine with a/c off, fans operate on low
4) Hot engine with a/c on, fans operate on high

Below are how the car operates.

1) Cold engine with a/c off, fans off
2) Cold engine with a/c on, fans off
3) Hot engine with a/c off, fans operate on low
4) How engine with a/c on, fans operate on low

Since the fans never go to high, the a/c doesn't perform.

The owner says he took it to the dealer in Austin, TX and they told him one of the fans were bad. This doesn't sound right to me. I would think if one fan was bad, only one would act out of the norm, but both do. I am thinking wiring or maybe a module, but I don't have much experience with this. Thanks for your expert help.
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post #2 of 12 (permalink) Old 04-10-2014, 04:44 PM
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- RADIATOR FAN & RE-CIRC. PUMP CONTROL
The two cooling fans are fitted beneath the radiator or (with a.c.) condenser/radiator package, and the coolant re-circulation pump is mounted below the header tank. Both the fans and pump are controlled by the engine management ECU using data provided by the engine coolant temperature sensor mounted in the back of the cylinder head.
The cooling fans are switched as a pair, and will operate at half speed (connected in series) when coolant temperature reaches 208f on rise, and switch off at 201f on fall.
The fans will also operate at half speed irrespective of coolant temperature if the a.c. is switched on and the compressor is running.
If coolant temperature rises to 217f, the fans will switch to full speed (connected in parallel), reverting to half speed at 208f.
The fans will also run at half speed, unless high coolant temperature dictates otherwise, when the a.c. is switched on and the compressor is running, or if the engine management system detects a fault with the inlet air temperature or coolant temperature circuits.
At road speeds in excess of 85 mph (135 km/h), equating to the fan stall speed, all fan functions are switched off.

A trinary switch fitted into the top of the receiver-drier senses the pressure of refrigerant and allows
system operation only within a pressure range of 2 to 32 bar (29 464 psi) in order to prevent system damage from too high
a pressure, or from compressor oil starvation damage caused by too low a pressure. A third switching point is
used to engage the two condenser fans at half speed at pressures over 17.5 bar (see also sub-section KH.5).
An additional safeguard is provided in the form of a high pressure relief valve in the condenser inlet pipe, which
opens at 38 - 41 bar.

Michael
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post #3 of 12 (permalink) Old 04-12-2014, 08:21 AM
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There have been some occurrences where the dealer has either switched the fan leads or not plugged one in when they performed the oil line recall causing issues.

05 Elise
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post #4 of 12 (permalink) Old 04-12-2014, 09:35 AM
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My first guess would be low refrigerant pressure.

-Ed
'08 Arctic Silver Exige S240
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post #5 of 12 (permalink) Old 04-12-2014, 01:47 PM
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I had a fan go out on my exige, the symptoms are different than yours. The fan would only come on with the high speed mode (ac on or hot) because the fans are power in parallel effectively bypassing the bad fan in the circuit.

Aj

07 Exige Phantom Black
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post #6 of 12 (permalink) Old 04-14-2014, 07:45 AM Thread Starter
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Thanks for the input guys. I bought the car. Now I just need to convince myself to not drive it so I have time to look into this issue. I am sure once it hits 100 in TX, I will get more motivated.
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post #7 of 12 (permalink) Old 02-20-2015, 02:12 AM
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u can force it to running high by earthing pin on the control relay box. u can also add a button ( made on mine) to push on the fans when u prefer
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post #8 of 12 (permalink) Old 03-26-2015, 07:15 AM
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just to specify pin 60 and 67 have to be jumped together, this make fans run always fast
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post #9 of 12 (permalink) Old 07-31-2016, 04:42 PM
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I'm trying to perform this mod to make the fan run at high speed when i'm stuck in jams or low speed traffic.
Can anyone please advise me where the control relay box is located? Is it under the front access panel on the "port side"?

2009 Elise S

Last edited by powersteer; 07-31-2016 at 04:50 PM.
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post #10 of 12 (permalink) Old 08-01-2016, 04:38 AM
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I have found the fans will run in high with the ac on in traffic via the Trinary switch

I think it would improve performance of the ac if they always ran on high with the AC on, but only in moderate temps as when it is hot they are already on high
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post #11 of 12 (permalink) Old 08-01-2016, 05:33 AM
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Quote:
Originally Posted by exigegus View Post
I have found the fans will run in high with the ac on in traffic via the Trinary switch

I think it would improve performance of the ac if they always ran on high with the AC on, but only in moderate temps as when it is hot they are already on high
Can you please elaborate further on whats a Trinary switch? How did you switch it to high?

2009 Elise S
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post #12 of 12 (permalink) Old 08-01-2016, 07:26 AM
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I didn't do anything, that is how it acts. I actually replaced the fan control module and it acts the same way, so it is not a mod. It does not appear to be the way the shop manual describes it

I would check the behavior of your system with a proper charge of 134 and a very hot day and see how it acts

Oh, and the trinary switch turns the ac compressor off for low pressure, off for too high pressure and turns the fans on at a certain pressure
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