My 1989 Volvo 240 keeps blowing FUSE number 8, which controls the radio and interior lights...a new fuse will last about 10-12 hours. What could be causing this?

I suspect a bad ground....because it always seems to be caused by a ground with errant voltages causing "brown out" conditions with the semi-conductor devices....chokin' on it's own voltages and blowing a fuse is not unheard of...what you must do is find the black 1/0 battery cable what connects to the chassis ground and wirebrush it until it's shiny and willing to make the 300 cca needed to start the car quickly...also look at the knock off labels on the top of your battery what would indicate the date of the first charge....five years old is too old, will start asking your alternator to give FULL output....constantly with the olde tyme battery....get a NEW battery....spend $120,00 for an Interstate battery their warranty will keep you happy for five more years~ probably once good ground is established (from your GOOD battery) to the chassis and to the engine block too, the components affected will start to behave themselves properly~ let's do it and find out~

are one of your speakers shorting?

Just got new alternator in feb, but I connected wires wrong and then had to get battery charged up. Yes, several of the speakers sound like they are blown or not working properly

PRETTY HARD TO HOOK UP THE WIRES WRONG BUT I'M SURE I'VE DONE WORSE MAYBE A TYME OR TWO. MAKE SURE THE WIRING TO OTHER COMPONENTS ARE NOT SHORTING OUT AS WELL. I HAD THIS PROBLEM WITH MY 88 740 STATION WAGON. THE BLOWER MOTOR FOR THE FAN WAS DRAGGING AND CAUSED THE FUSE BOX TO HEAT UP AND START TO MELT THE BOX. CAUSED ALL KINDS OF PROBLEMS. GIVE EVERYTHING A QUICK ONCE OVER TO BE SAFE. RAGONZALESSR

take your time....follow the wiring diagram...put it right...only will be a minor investment, but it will be correct then.~

WHILE YOU TRACK DOWN THE WIRING YOU ARE ALSO LOOKING FOR POSSIBLE BARE WIRES AND CORROSION IN THE FUSE BOX WHERE THE FUSES AND RELAYS PLUG INTO.THE FUSE BOX. I ALSO HAD THIS PROBLEM ON MY 88 740 WAGON. ONE OTHER PROBLEM I HAD WAS THE WIRE ON THE GEAR SHIFTER THAT ACTIVATES THE OVERDRIVE, AUTO TRANNY, HAD GOTTEN PINCHED AND WAS POPPING IT'S CORRESPONDING FUSE. THE QUICK FIX WAS TO TAPE THE WIRE RATHER THAN TAKE IT APART AND BUY ONE TO REPLACE IT. RAGONZALESSR

It sounds like you may have a problem with a bare wire or a faulty switch on the door jamb. Keep in mind, though, that tracking down problems in these cars can be a nightmare as they are multiplexed. Everything works off feedback on them. The strangest things happen is anything is not exactly right. On Ma's 90, the negative power window wire got pinched and was shorting out. Don't ask me how a ground to ground can short, but it did. When you closed the door, the rear defroster would turn on! Put in a turn signal bulb wrong, and the headlamps come on instead of the brake lamps. Be careful when you run the wires to make sure everything is perfect. Also if there are any after market replacement parts, put in the Volvo originals, as the feedback is different. Good luck!