Hi duncan64,
Welcome to the Community.
I would suggest you to perform component test on the wireless card using the Dell PC Diagnostics. Please click the link mentioned below to download Dell PC Diagnostics:
If the test fails, wireless card needs replacement.
If the test pass, drivers and the BIOS need update. Please let me the know the operating system installed so that I can provide you the driver accordingly.
Thanks & Regards
Manshu S
#iworkfordell