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Author Topic:   No Start From Bad Solenoid

merc125 posted 05-20-2007 07:25 PM ET (US)
I was faced with a no start condition today on my 2000 Mercury 200. I found a bad starter solenoid. You can see the contacts are gone:
http://pic15.picturetrail.com/VOL583/4074976/8506148/254017769.jpg
Could a low voltage condition at the coil of the solenoid cause it to fail? What is the minimum acceptable voltage at the coil? I was reading 11.5 volts at the coil under load. MartyD
jimh posted 05-20-2007 08:45 PM ET (US)
The solenoid coil voltage should be the battery voltage, minus any drop in the starting circuit path which should be minimal. Usually the voltage travels from the motor to the remote ignition switch, through a neutral start safety switch in the remote throttle and shift, then back to the motor to the solenoid coil. When you measure the voltage at the coil the engine is usually cranking, and this will drop the battery voltage. So a reading of 11.5 sounds about right.
If the picture is showing the contacts from inside the solenoid, they look like they've been arching and have burned up. A new solenoid is not very expensive, probably only $25. You can burn up the contacts faster if the solenoid chatters on and off. That might happen if the battery voltage sags too low under cranking.

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Author	Topic: No Start From Bad Solenoid
merc125	posted 05-20-2007 07:25 PM ET (US) I was faced with a no start condition today on my 2000 Mercury 200. I found a bad starter solenoid. You can see the contacts are gone: http://pic15.picturetrail.com/VOL583/4074976/8506148/254017769.jpg Could a low voltage condition at the coil of the solenoid cause it to fail? What is the minimum acceptable voltage at the coil? I was reading 11.5 volts at the coil under load. MartyD
jimh	posted 05-20-2007 08:45 PM ET (US) The solenoid coil voltage should be the battery voltage, minus any drop in the starting circuit path which should be minimal. Usually the voltage travels from the motor to the remote ignition switch, through a neutral start safety switch in the remote throttle and shift, then back to the motor to the solenoid coil. When you measure the voltage at the coil the engine is usually cranking, and this will drop the battery voltage. So a reading of 11.5 sounds about right. If the picture is showing the contacts from inside the solenoid, they look like they've been arching and have burned up. A new solenoid is not very expensive, probably only $25. You can burn up the contacts faster if the solenoid chatters on and off. That might happen if the battery voltage sags too low under cranking.