Topic: 1940 electrical short


grump40    -- 09-13-2010 @ 12:20 PM
  There is a short between the wire from the ignition switch and the circuit breaker and instrument gauge wire to the switch. Could the problem be in the circuit breaker itself ? The car will start and run if the instrument wire is not connected at the switch. Thanks for any help !


supereal    -- 09-13-2010 @ 12:37 PM
  If the car starts OK with the accessory (instrument) wire disconnected at the switch, be sure that the connection of that wire at the switch is not grounding on the metal case of the switch, a common fault. If it is OK, follow that wire and disconnect it at each component until the short disappears. If it is a "dead" short, place a test light in series with the switch and wire and check until the light goes out. If the "circuit breaker" you are referring to is in the headlight circuit, it shouldn't be the cause unless the lights are turned on. The gauges "find" ground thru the senders. If those wires are shorted between the guage and sender,, the gauges will swing over to the maximum and stay there.


supereal    -- 09-13-2010 @ 12:38 PM
  If the car starts OK with the accessory (instrument) wire disconnected at the switch, be sure that the connection of that wire at the switch is not grounding on the metal case of the switch, a common fault. If it is OK, follow that wire and disconnect it at each component until the short disappears. If it is a "dead" short, place a test light in series with the switch and wire and check until the light goes out. If the "circuit breaker" you are referring to is in the headlight circuit, it shouldn't be the cause unless the lights are turned on. The gauges "find" ground thru the senders. If those wires are shorted between the guage and sender,, the gauges will swing over to the maximum and stay there.


supereal    -- 09-14-2010 @ 9:04 AM
  Sorry for the double response. My system has been acting up. In consulting the circuit diagram for '40, the accessory side of the switch feeds only the gauge sets, in the original configuration. If you have anything else connected, such as a radio, I'd disconnect that and see if the short is cleared. The circuit breaker is connected directly to the battery at all times, and the only non-switched part is for the stoplight circuit. The rest goes thru the headlight switch, and should not be connected to the ignition switch. If you need wiring diagram, I can scan and post it.


37RAGTOPMAN    -- 09-14-2010 @ 3:31 PM
  How old is the wiring ?
be sure to check the back of the gauges so there is no bare or wires shorting,
if the short is south of the circuit breaker it should shut down before you have big problems.
if you want to check for a short and have no electric meter,you can use a test light, disconnect the ground cable on the battery, put the test light from the pos terminal to a ground,
if it is lighted you have a electrical draw.
just keep on disconnecting till the light goes out,you have found the problem,
important just do one at a time so you narrow your search.
and keep track of what you disconneted.
hope this helps 37RAGTOPMAN an KEEP on FORDIN,,,,!!
if you have old WIRING ,REPLACE WITH NEW WIRE LOOM, and install a MASTER DISCONNECT SWITCH,for SAFTY SAKE,


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