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How differentiate low speed and high speed fan ?

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Hi all,

My car is overheating slowly in start stop traffic and it makes me wonder if my fans are actually going into high speed mode...

When i turn on the AC, both fan spins. Fan is pretty loud... does that mean its in high speed mode ?

Thanks !
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2006 Lotus Elise BRG
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Hi all,

My car is overheating slowly in start stop traffic and it makes me wonder if my fans are actually going into high speed mode...

When i turn on the AC, both fan spins. Fan is pretty loud... does that mean its in high speed mode ?

Thanks !
How did you make out with your other checks and maintenance? Water pump and thermostat both check out? Did the coolant look okay? Not gelled up?
When you re-bled the system did you use a device like the airlift?
 
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Sounds like some air is still trapped.
 
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Lotus Radiator fans – Operation

The cooling fans are switched as a pair, and will operate at half speed (connected in series) when coolant temperature reaches 98°C (208°F) on rise, and switch off at 94°C (202°F) on fall.

Both fans will also operate at half speed irrespective of coolant temperature if 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.


If coolant temperature rises to 103°C (217°F), both fans will switch to full speed (connected in parallel), reverting to half speed at 98°C (208°F) on fall.
 

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Discussion Starter · #8 ·
How did you make out with your other checks and maintenance? Water pump and thermostat both check out? Did the coolant look okay? Not gelled up?
When you re-bled the system did you use a device like the airlift?
I got the following changed,

  • New pro alloy single pass rad
  • New top mounted fans
  • New AC condenser
  • New Billion 75C low temp thermostat
  • New Rad hoses
  • Fresh Coolant, both bleeder valve shoots solid coolant when pressed
 

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Discussion Starter · #9 ·
Lotus Radiator fans – Operation

The cooling fans are switched as a pair, and will operate at half speed (connected in series) when coolant temperature reaches 98°C (208°F) on rise, and switch off at 94°C (202°F) on fall.

Both fans will also operate at half speed irrespective of coolant temperature if 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.


If coolant temperature rises to 103°C (217°F), both fans will switch to full speed (connected in parallel), reverting to half speed at 98°C (208°F) on fall.
Hmm interesting... say in the morning, when i switch on the AC only 1 fan is turned on (i can see because its top mounted), when it gets to 85C/185F both fans come on. However, Im not sure if the fans are on low or high speed, both fans are spinning
 

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Discussion Starter · #10 ·
This is the right question. Fans aren’t bad but continuing past 210F with them on while stationary is. So many people freak out about 200F it’s like there isn’t a user manual…

Yes my exact sentiments... both fans are on once temp reaches 85C/185F, but it has trouble stablising the temperature and it keeps going up north till 225F...

Im not even pushing the car. With AC on and normal city driving.
 

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Yes my exact sentiments... both fans are on once temp reaches 85C/185F, but it has trouble stablising the temperature and it keeps going up north till 225F...

Im not even pushing the car. With AC on and normal city driving.
Sounds exactly like air in the lines. Try re-bleeding a couple times. Even with a vacuum bleeder it takes me several drives with bleeding each time to get all the air out
 

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Can also park on a steep angle, nose down which should push air back to the engine. Dont tighten the overflow reservoir cap so the system can burp itself.

Also, I am sure the engine sensor which monitors temperature for computer and dash is ceramic (organic), so it has a limited life.
 

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Discussion Starter · #14 ·
Can also park on a steep angle, nose down which should push air back to the engine. Dont tighten the overflow reservoir cap so the system can burp itself.

Also, I am sure the engine sensor which monitors temperature for computer and dash is ceramic (organic), so it has a limited life.
Let me try this ! and report back.

I really hope its just air and not the puller fans i have installed..
 
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