Windows – Problems with Broadcom WLAN and Windows 8.1

I have read : Windows 8.1 update effectively disabled wireless networking
It didn't help.

I have just recently bought a Lenovo M5400 laptop and installed Windows 8.1 x64.
According to the support website, the wireless card is : Cbt BCM943142HM 1x1BGN+BT4.0 HMC wlan

I've had multiple problems with my wireless internet connection since I installed it using the drivers on the support webpage. They gave me two drivers for Win 8.1 x64 for this card and I installed both of them separately to test it out.

Currently the device manager show me two possible drivers to use :
– 1×1 11b/g/n Wireless LAN PCI Express Half Mini Card Adapter (which I assume is the generic Windows driver for this card)
– Broadcom 802.11n Network Adapter

The wireless AP is a TP-LINK Wireless Lite N Router WR741ND that runs in bgn mixed mode on 40Hz channel width. I sit relatively close to it and have full signal. I've also checked and there is no interference on the channel.

The symptoms are as follow :

• After a while of watching a video on YT for example the icon for the connection shows that I have limited connectivity.
• While I have limited connectivity I can run the windows troubleshooter and it resets the adapter and the connection works again for a limited period of time.
• When there is connectivity, using the ping tool there are relatively short periods when there are lag spikes. However the lag spikes don't seem to influence the limited connectivity problem since the episodes are separate.

I also have a PC that is connected with a cable to the router and another laptop that also uses a wireless connection to the same router. They do not show the same symptoms.

There is an extensive thread here but the technical support from Microsoft on this issue is less than helpful. I've also tried contacting Microsoft Technical Assistance but they only seem to prefer to talk via telephone and I'm uncomfortable doing that. I really don't know why Microsoft even offers the option of live chat.

Any help would be greatly appreciated.

On an off note :
I've had a similar problem with another laptop while using Windows 7 and a Qualcomm card. The issue was solved by using an unofficial driver I found on a Czech webpage. Sadly I can't find one for this card.

Later edit :
Nothing worked. Installed Windows 7 and it worked perfectly.

Later later edit :
It did not work perfectly. The same thing kept happening just at less frequent intervals. I bought a new Intel wireless card and plugged it in but the BIOS guard kicked in and it didn't let me boot up.

It seems you cannot put a wireless card that's not signed by Lenovo. Which sucks and no one told me about it but apparently it's due to some sort of FCC regulation (figures as much, I didn't know that the country that I live in is subject to US commercial regulation and law).

Now I've lost the warranty since I opened my laptop to change the wireless card. This doesn't matter as much since it was "working as intended" if you can call it that. There seems to be a way to crack it by writing the ID of the old card on the new one but it's quite dangerous since even the smallest mistake can burn either the motherboard or the card and I'm not willing to risk it since this Lenovo Essentials M5400 laptop is one that Lenovo considers garbage-tier but in my country is worth about a two month salary for regular people. (long sentence is long)

I have fixed this problem by disabling the original card and using an external USB wireless card. Hooray for bad design and bad hardware. Lenovo went from respected brand to canned malarkey producers in my book.

I wrote this in case anyone wants to buy this particular model. If you're thinking of buying it, just don't. I have nothing to say about other models.