Easiest fix is usb-bluetooth adapter (get a usb-hub too if you don’t have a spare usb-port), I’ve used usb-bluetooth adapter when bluetooth-electronics have died. But since you have a weak signal, that really does sound like an antenna issue, not electronics issue. If that iMac is going to be opened again, verify blue-tooth antenna cable plugs look ok with center-pin not bent, and are antenna cable tiny right-angle plugs are fully seated correctly on tiny coax jacks on logic board. Make sure the little black coax antenna cables look ok: not crimped/knicked. After re-seating antenna cable, test blue-tooth while you still have it apart. Best to do bt tests with no other external devices connected except a usb-keyboard and usb-mouse… temporarily turn off your bluetooth keyboard and/or bt mouse while testing.. You might install homebrew then do brew search blue
to find utilties to help do bluetooth tests, like bluetoothconnector blueutil
and others. I’ll post back here if I find an easy way to confirm bluetooth signal quality (strength, s/n ratio, etc.) If you have a spare bluetooth antenna with the same type of plug from an old dead laptop/desktop, you could temporarily connect that in place of the iMac internal antenna. If bluetooth works with temporary antenna, then you may need to repair/replace the bluetooth antenna inside your iMac. Or just skip all this troubleshooting headaches, get a usb-bluetooth adapter, and turn off the internal bluetooth forcing it to use only the usb-bluetooth adapter for all bluetooth connections.
crwdns2934105:0crwdne2934105:0
crwdns2934113:0crwdne2934113:0
crwdns2915270:0crwdne2915270:0
crwdns2889612:0crwdne2889612:0
0