Which fuse controls the 12-volt outlets. I have

Look in your owners manual for the accessory fuse. That line turns off. Also, consider a 12 volt relay between the seat and your power source. A small toggle switch will work well for a relay.

wire it up to the spare in your fuse box. one side is on only when your ignition is on .fitted with an online switch .to switch on and off.

Where do you have a 9 volt? I'm assuming you mean the outlet that we used to call the cigaret lighter? If so, it's a 12 volt outlet. Its pretty common for this fuse to blow, I'd definitely check that first. Get a few fuses because it likely blew from a bad accessory you plugged into the outlet. Also, try a few different accessories and verify that it's not an issue with the one you're plugging into it. If you replace the fuse and it blows again then the problem is being caused by whatever you're plugging into it.

I think you need to look inside of the sockets for foreign objects such as change or foil from gum wrappers. This is the most common cause of this problem. If it is all clear we need to unplug both and put in a new fuse, plug in one and then the other, see which one is the bad socket.

remove electrical connector from blower moter .With car running test voltage at connector if you have 12 volts or better at connector replace blower moter if not check fuse, replace fuse if blown.

Look in the owners manual it will tell you what fuses are what, if not you have to test each fuse with a test light

You mean there seems to be no power to the vehicle's lighter unit outlet.

This lighter unit outlet is normally wired through its own fuse so check the fuse panel in the car for a blown fuse. If blown it must be replaced with a fuse of the correct amperage. The owner's manual will show you where the fuse is located.

Before you check the fuse just check the cigarette lighter outlet with another plug-in device if you have one such as a portable 12 volt tire compressor or a 12 volt plug-in auxiliary light. It could be that if you are using a charger from the outlet, the charger plug or wiring may be faulty rather than the car's power outlet itself. (These outlets don't usually give trouble unless the wiring has been messed with or the outlet itself has been damaged or abused).

If no device works from the lighter power outlet check the fuse as it may be blown.

Sean
Voluntary contributor.

check for voltage with test light suspect that wire at back of outlet pulled off

Even thought the plug in is 12 volt. It's ouput is different. Most electronics have different ranges from 3-9 volts.
Does the 12 volt charger put out 12 volts? If so, it would burn up the electronics' capacitors on their power supplies.
How is the car's electronics doing? Are they too failing? If so, that would be a faulty voltage regulator, if not, I would hook up anything you use to the radio wires.
You cannot plug in anything directly to battery no matter what the person told you. Batteries charge, than release charge, a contiuous cycle. The power output is speratic and anything hooked straight up to the battery will need a fuse.

under the hood on the driver side