I stopped to put air in the tires and the horn went off. I unplugged the horn and stopped at another store and at that turn the key off and the engine would not shut off. The overdrive arrow light came on, no other lights came on. Pulled the coil to shut it off. Need help. What is causing this. Thank you

 

The ignition switch assembly is probably worn out.

 

There are a few reasons why this does happen. Most commonly, it's a bad starter. You can either buy a new starter, or rebuild the one that you have now. Second reason applies to diesel models. Since diesel engines use compressed heat to ignite, instead of a spark, a shutoff solenoid is used to cut the fuel source off. However, over time, this solenoid can fail, preventing the engine cycle to break (basically, it will keep running). But from what you're describing here, it really sounds like the battery terminals were switched... a bad mistake made when replacing the battery. If this occurred, then your car not shutting off is the least significant problem. It would explain that the horn went off because the circuit was reversed. Bigger problems include the destruction of your alternator (almost immediately), and the complete compromise of your car's electrical system.

Please list any recent services you've had on your vehicle and include the model information. As you can see, the engine type is a very important factor in this problem.

 

Hmmm, fascinating!
Starling, please DO keep us posted!

 

Thank you. The battery cables are not switched. Ignition switch is ok. Not a diesel. She still cranks fine, just have to pull the coil to shut her off and disconnect battery so the dash lights don't run the battery down. Could there be a problem with the computer? Or could there be a short somewhere? Any other ideas?

 

A "short" is always a good answer but unfortunately means little, it's pretty vague... I said the igniton switch because they are known to cause all kinds of weird gremlins, similar to what you experience. How do you know it's not the switch?

 

UPDATE: While the car was running, I disconnected the wires from the key switch. The engine continued to run. I pull the coil wire to turn it off. Pull the battery cable to turn the dash lights off. Put the battery cable back on, dash lights remained off until you turn the switch back on. Hooked the horn back up and it is no longer going off however the horn will not sound if you press the buttons. The wires in the steering column look fine no breaks or frayed wires.

 

Any chance this car may have been somewhere near the Mississippi Gulf Coast late August 2005?

I had a 240 floatinto the woodson Hurricane Andrews 16 foot storm surge(yes volvos float). Not withstanding the army corp had to air crane it out because they were protected woods, the car neverwasthe same.