Possibly faulty temperature sensor on Acer 7741G?

Last week I noticed that my laptop was starting to overheat a lot e.g. becoming almost too hot to touch and decided to look into it. This was happening in particular when watching HD video files and after approximately 1 hour the laptop would shut itself off. I installed speed fan and that reported high CPU temperatures and a GPU core temp in excess of 100 degrees centigrade. I also noticed that the fan wasn't making any noise or spinning at all and assuming that to be the cause I ordered a replacement fan and heatsink assembly as well as some thermal paste remover and Mx-2 paste. (The fan was making some noise a few months ago so I cleaned it with some compressed air at the time which seemed to fix that).

I installed the new heatsink and fan along with the new thermal paste yesterday and the temps had dropped to below 40 degrees C for both CPU cores and the GPU core but the fan still didn't seem to be on so I ran furmark for around half an hour which didn't affect CPU resources much at all but pushed the GPU core to a peak of around 104 degrees c and still the fan didn't move. I also flashed an unlocked version of bios 1.26 last night but by that time the laptop had started to get hotter again and was powering itself off so I left it to cool overnight.

I've switched it on this morning and it works fine but after around an hour of normal use speed fan reports the following:

Hdd 0: 43c
Temp 1: 73c
Temp 2: 51c
GPU: 76c
Core 0: 71c
Core 1: 73c

CPU usage is currently around 5% and still the fan doesn't move at all.

Given that the fan and heatsink assembly had already been replaced and as I understand fan control is handled on-chip by the CPU and not by a controller on the board does this mean that the CPU is failing? I just wondered if anybody could shed any light on this as a replacement CPU will cost around £100 I think for an i5 or i7 (its currently running the factory supplied i3 350m and dedicated HD 5470) and I don't really want to throw any more money after bad if this can't be fixed at all.

CPU-Z stats: CPU-Z Validator 3.1

Speedfan doesn't display the stats for the fan at all by the way (although I believe that this is common for Acer laptops) and even in the unlocked version of the BIOS I cannot find any field which displays or allows management of the system temperature.

Thanks.

 

Sorry for the double post but I have just installed CPU ID Hardware Monitor as well and like Speedfan it doesn't detect the fan at all.

The fan connection cable was definitely reconnected before I reassembled the laptop because I double checked it.

 

Fan is not being detected in general on almost all Acer notebooks (save fer Aspire Ones) so that's not a big deal.
CPU is not the culprit either- if the fan is not rotating (and assuming it's connected properly) it might be an issue with the connector itself.
Could you see if there is any voltage on the connector?

 

Thanks for the quick reply. I had a feeling that it could be an issue with the connector but I'm not sure how I could go about testing that really. Would it be a case of checking it with a multimeter or something or is there an easier way?

I really hope that it isn't the connector since I have no idea how I could go about even sourcing a replacement let alone re-soldering it and I'm thinking that to buy a replacement board would probably cost almost as much as a new laptop.

 

Multimeter is the only way.
You may also want to check if something isn't blocking the fan- sometimes if you route a cable the wrong way while assembling the notebook it may get jammed against the fan preventing it from spinning even though the fan is functional and powered.

 

Thanks, I think the cabling is fine to be honest but I could definitely double check it.

So the best route is to disconnect the fan from the connector, touch the two pins on the connector with the multimeter and see if there's any voltage on there then?

If the connector is broken (which unfortunately is probably likely) then can these usually be sourced/replaced or do I just need an entirely new board. I did a google search on this and also saw that it's possible to solder the connector wires directly to the points on the board but I would prefer to avoid anything like that if I can do.

This is a huge mess to be honest and I'm quite annoyed by it since the laptop isn't even 2 years old yet.

 

In case it's the connector you won't have to replace the whole board- if you don't feel like doing it yourself someone at a service center will do that for you (doesn't have to be Acer center either)

 

Do you know where I could get a replacement connector from though? To be honest the only places local to me are small computer and mobile phone repair stores and I trust them less to do it then myself.

Which points would it be best to probe with the multimeter to check that the connector is receiving voltage?

 

The connector pins itself are the safest. Fan gets power immediately after you press Power button so it should be possible to test it on completely disassembled notebook too.

 

Thanks, I'll take a look at it and see what I can do. If it does turn or to be the connector then I'll see if I can fix it or just sell the machine for spares/repairs. Do you know if ours usually easier to solder the wires straight to the board or to replace the connector itself? I can look into local repair shops but I doubt that any of the trustworthy ones would be willing to do this for a reasonable fee.

I'm still not even completely sure where I would be able to source a replacement connector from to be honest.