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HP Recommended
Elitebook 840 G2
Ubuntu LTS

I bought an Elitebook 840 G2 for my brother.

 

The laptop is in wonderful condition. I put in 16GB Ram and a hard drive. Now that the battery has arrived I have noticed that the laptops fan is on when the laptop is off, and vice versa.

 

I can only imagine this is a simple connector/wiring problem.qher 

 

Is it possible that the fan connector is reversed?

 

Some connectors can only go on one way around. Others can be reversed.

 

Or the wires could have been switched.

 

Where can I find the wiring and connector specification? Is it in the manual for the laptop, or is this information limited to repair people?

 

1 ACCEPTED SOLUTION

Accepted Solutions
HP Recommended

Sorry but I dont think it's a wiring switching problem. Even if the wires are reversed, either the fan would turn in the wrong direction or it would not turn at all. But in no case it would run when the PC is off and vice versa. No way!

If it turns when PC is off it means it get "power" from motherboard. So I think the motherboard has a problem.

 

View solution in original post

10 REPLIES 10
HP Recommended

Here is your Service Manual:

 

Manual 

 

So are you saying the fan is running when the laptop is fully powered down? Hate to say I am skeptical about that. 

HP Recommended

Thanks for the manual. Page 83 has the fan. I will see if looking up the part tells me something about the connectors. 

 

If the laptop is turned off but plugged in then the fan runs.

 

If the laptop is turned off, with the battery plugged in, but unplugged then the fan runs.

 

If the laptop is turned on the fan turns off.

HP Recommended

hey,

 

It should do the opposite. When PC is on (pluggen on battery on AC power) fans should turn. At the opposite, when PC is off (plugged or not, battery or not), fans should be off too

HP Recommended

"It should do the opposite"

 

Yes, which is why I thought the problem is something simple like the fan connector being put in the wrong way around.

 

Here is a picture of the connector. I haven't gotten to it yet. I will need to get a torx screwdriver. My first stop was this board to see if there is some other cause. Since I posted I saw a couple of other people had this exact problem with the same model.

 

https://www.ebay.co.uk/p/1251240902

HP Recommended

Of course it should do the opposite. The fan connector is one-directional. Only one way to plug it in. I found some stuff on the internet about similar problems which seem to focus on the sleep state and the laptop not actually turning off and issues with Intel Management Engine. I have also seen desktops do this when the motherboard is going bad. 

HP Recommended

"Of course it should do the opposite. The fan connector is one-directional."

 

I got the laptop second hand, not from HP, so I don't know if this fan is standard or fitted in a regular way. 

 

I can see the wires which go to the fan without opening everything up. The wires are white, black, yellow/orange, and red. I can't see the order they are in.

 

The wires should (1) Ground, (2) +12v, (3) Tach/Signal/Sense and (4) Control/PWM. 

 

Black and Red should be (1) and (2) respectively. This picture should tell me where they should go into the connector. When I open the laptop up I will see what the situation is. 

 

https://www.ebay.co.uk/p/1251240902

 

This is a bizarre situation, with the fan off when the laptop is on, but on when the laptop is off. It is hard to imagine this could be a wiring switching problem. If the fan was on regardless of whether the laptop was on it would be more understandable as a fault. Ditto if the fan was full on when the laptop was on, but off otherwise. 

HP Recommended

There is just no way its a wiring issue. I can't imagine someone rewiring the fan. Would make zero sense. You could replace the fan. They are not very expensive but I think it would be wasted money. 

HP Recommended

"You could replace the fan."

 

Why would I? It is working. Unless there is a circuit on the fan which could be causing the problem I don't see a reason for changing it.

 

 

HP Recommended

Sorry but I dont think it's a wiring switching problem. Even if the wires are reversed, either the fan would turn in the wrong direction or it would not turn at all. But in no case it would run when the PC is off and vice versa. No way!

If it turns when PC is off it means it get "power" from motherboard. So I think the motherboard has a problem.

 

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