JD 620 electrical question

Parked my 620 outside. Started it every couple of weeks during the winter with no problem. All of a sudden it won't start and I notice the fuel gauge dosen't register when the switch is turned on. The lights don't come on either. The battery is up and the starter turns it over. Has fuel and compression. Is there a simple problem that would cause this condition? Like a fuse link or something? Appreciate any ideas.

Thanks in advance ... Norm43

Problem with ignition switch... trace wire coming from starter to ignition switch and test it for voltage.. if voltage is present but no voltage comes out on any of the ignition lugs, then replace the switch.

There must FIRST voltage getting to the switches BAT input terminal so the lights and ignition etc can work. Then as Rob points out, the switch itself needs to work. I theres no lights or no power to the ignition either nor does the gauge work Id suspect the voltage source that feeds the switches BAT input terminal is bad/open. (See below, the wire that feeds it comes from the ammeters output and the ammeters input comes from a wire down to starter (can get cut/burned open) or else direct from battery (may have been jury rigged in past)

ALSO,,,,,CHECK BATTERY CABLES N CONNECTIONS AND ESPECIALLY THE GROUIND


The voltage source TO the switches BAT input terminal is derived EITHER from the Load (NOT battery/starter) terminal on the (Insure BOTH ammeter terminals have hot battery voltage) ammeter, or else the LOAD terminal on a 4 terminal Voltage Regulator

SO FIRST OFF INSURE THERES HOT BATTERY VOLTAGE ON BOTH SIDES OF THE AMMETER AND ON THE BAT INPUT TERMINAL ON THE SWITCH

If theres no volatge getting to the switch, trace back n see where it gets lost. If there is voltage to the switch then see if the switch is bad i.e. isnt sending hot voltage to lights or ignition when turned ON

Next if theres no voltage at switches BAT input, see if theres a good wire from the Load side of ammeter or L terminal if you have a 4 terminal Voltage Regulator,,,,,,If thats good, see if theres hot battery voltage on BOTH sides of ammeter???? IF NOT the feed wire which supplies hot battery voltage to the ammeters Supply input terminal is bad.........

The input to the supply side if the ammeter may be fed from the starter where the big battery cable attaches CHECK THAT WIRE !!!!!!!!!! Or it may be fed directly from the batteries hot ungrounded post

Look at the wiring diagram and trace for a good hot battery feed from the starter to ammeter,,, out of ammeter to switches input,, AND ID SUSPECT THE WIRES BAD FROM STARTER UP TO AMMETER OR FROM AMMETER TO SWITCH if absolutely nothing works. HOWEVER if some things work (like lights or igntion or fuel gauge) then Id suspect the switch like Rob was talking about

ONE FINAL THOUGHT Id check ALLLLLLLLL battery n ground connections cuz if theres a bad battery connection or a bad ground NOTHING will work.....

John T

Wiring Diagram

Thanks Rob ... I had checked the obvious things like battery connections and grounds already. I suspect the switch becasue the starter works and when it is turning over the fuel gauge works as well so the power must be feeding back through the starter.

It snowed last night so I will get back to this in a couple of days when the weather shapes up.

Thanks for the diagram. It will help a lot with the detailed tracing.

Thanks again ... Norm43

The starter switch is merely a push down saddle mount to starter mechanical type which doesnt have anything else to do with the rest, except for that below.

HOWEVER when the starter switch is engaged its small lil side terminal backfeeds hot voltage up to the coil (or low output side of ballast resistor, same thing electrically) which, therefore, effectively backfeeds the switch also (albeit via the ballast)...What this means is even with NO POWER TO THE SWITCHES BAT INPUT TERMINAL VIA THE WIRE FROM AMMETER,,,,,,,,While shes cranking (with switch ON) the coil can still fire and other switch functions (say lights or fuel gauge) can work (while cranking) although at ballast reduced voltage.......

SOOOOOOOO, once more, Id insure theres hot battery voltage getting to the switches BAT input terminal cuz if the switch isnt the problem (I cant say for sure sittin here, perhaps it is??) I SUSPECT THERES NO INPUT VOLTAGE ON THE SWITCH which, if original, comes from the Load side of the ammeter via a wire.

Let us know if theres voltage getting to the switches input ???? and if so then It may be a switch or other wiring problem.

One other note, for safety when the ign switch is off the coils output (to distributor) gets grounded via a terminal labeled Mag on some switches so if thats mis wired it could cause problems even where the switch is fine..

John T

Thanks again John. Sorry I mistakenly called you Rob yesterday. Forgive me cause I'm old but still like tractors. Your advice has been great. Still cold and snowy but it will warm up in a couple of days and I will check the switch situation out then. ... Norm43