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Classic/Antique Car Repair/1971 Mustang Convertable won't turn off

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Expert: - 5/26/2011


Question
I have a 1971 Mustang convertible that has unfortunately sat in my garage too long.  It has a 351C, FMX Auto trans, Ram Air, power top, power windows, AM/FM radio and believed to have been built for the president of Philco Radio.  Anyway, it now starts with the turn of the key, but won't turn off when I turn the key back to shut it off.  The car keeps running until I pull the coil wire. Is this the ignition switch or any other ideas how to correct this?  Thank You. - Confused in Massachusetts

Answer
The two most common causes for this is either a defect in the ignition switch or a defect in the starter solenoid. To check, when the engine is running and you have shut off the ignition, remove both of the small wires from the solenoid. If the engine shuts down then the solenoid is defective. If the engine keeps running with the two small wires removed from the solenoid, remove the connector from the back of the ignition switch. If the engine shuts down the switch is defective. If the engine does not shut down disconnect the plug from the alternator voltage regulator. If the engine shuts down then the voltage regulator is the culprit.

Classic/Antique Car Repair

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Brad Sears

Expertise

All automotive including antique and collectible. However if the car has been modified I can only answer in general terms and maybe get you pointed in the right direction.

Experience

Automotive tech instructor. Syndicated auto columnist 1970's though the early 1990's. Syndicated auto radio talk show, Ask Brad About cars, CBS Radio 70's through 90's TV Show "Last Chance Garage" 1980's PBS-TV syndicated. Auto instructor for the following companies: Fram Autolyte Holly Carter AMF Ford Motor University Of Conn Blue Hills Technical School Sugar River Technical Center Grew up in a family garage in Needham Mass and turned wrenches from the age of 14.

Publications
Manchester Union Leader, Nashua Telegraph, Motor Service Magazine, Yankee Magazine, Popular Mechanics (Saturday Mechanic early 80's), Los Angeles Times, New York Times, and lots more.

Education/Credentials
More than I care to remember. Basically Franklin Technical Institute in Boston, Northeastern University, Fitchburg State Teachers College, Tufts University, and a lot of factory schools along the way.

Awards and Honors
Moto Award winner. And much more.

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