The Ford Barn - View Single Post

gearhead1952 · 07-07-2014, 10:18 PM

No running an alternator. The collapsing magentic field of the coil in the starter solenoid induces a large spike on the power line that can kill electronics. If running the pertronics ignition or have other electronics you need a diode to suppress the spikes. If you look on newer ford solenoids they are stamped diode suppressed indicating a diode inside. Need one on all devices with a coil of wire like heater, wipers, horn, relays. Use a simple 1n4005 diode from radio shack. In theory should only need one on the main power line but they are cheap and the starter solenoid is the worst culprit so start there.

07-07-2014, 10:18 PM	#17
gearhead1952 Senior Member Join Date: May 2010 Location: Julesburg, Colorado Posts: 714	Re: Dash gauges don't work No running an alternator. The collapsing magentic field of the coil in the starter solenoid induces a large spike on the power line that can kill electronics. If running the pertronics ignition or have other electronics you need a diode to suppress the spikes. If you look on newer ford solenoids they are stamped diode suppressed indicating a diode inside. Need one on all devices with a coil of wire like heater, wipers, horn, relays. Use a simple 1n4005 diode from radio shack. In theory should only need one on the main power line but they are cheap and the starter solenoid is the worst culprit so start there.