[AT] Checking the grounds

Brian VanDragt bvandragt at comcast.net
Fri Nov 21 21:26:12 PST 2014


That rear light is grounded through the seat frame which doesn't have a very
solid ground to the tractor chassis because it slides fore and aft for
adjustment.  An added ground wire from the lamp to the battery box will help
that too.
Brian

-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Dean Vinson
Sent: Friday, November 21, 2014 9:02 PM
To: 'Antique tractor email discussion group'
Subject: [AT] Checking the grounds

This evening's chore was to get the headlight on the left side of the 620
working; the one on the right side already worked.   I'd picked up a spare
sealed-beam lamp a while ago but hadn't gotten around to messing with it
until tonight.  Sure enough the old one tested bad, but just replacing it
with the new one didn't have any effect.   Looking a little closer, I
realized the circuit wire to the lamp from the light switch was broken right
at the spade lug on the bottom of the lamp housing.   That was easy enough
to fix, and the circuit wire showed 12 volts on the voltmeter with the light
switch on, but still no luck getting the lamp itself to come on.
Fortunately, I thought I heard a voice from the direction of Shelbyville,
Indiana, saying "Check the grounds..." so I unbolted the lamp housing from
its support arm, wire-brushed the contact surfaces, put everything back
together, and darned if that 12-volt lamp isn't mighty bright.   Thanks,
Farmer.

After declaring victory on the headlight I started looking at the rear lamp,
which didn't work either.   Turns out the circuit wires are cut right by the
base of the tractor seat and the remainder that ought to run to the light
switch is missing.  I don't have the right type of wire on hand to fix that
so it'll have to wait until tomorrow, but I went ahead and tested the rest
of the system to see what else I might be up against.  To my pleasant
surprise the lamp itself works just fine, and is the original type with a
second bulb behind a small red lens to give the operator the option of
switching on the white rear light for field work or the red rear light for
driving on the road at night.  (I don't foresee driving this tractor on the
road at night, but that's a neat little design feature.)   Anyway, looks
like it won't be hard to get the rear lamp back in operation also, although
the ground seems a little iffy there too.  There's a little flexible
perforated brass strip riveted at one end to the inside of the lamp housing,
and sticking out into the housing so the other end should press against the
metal bulb socket at the base of the lamp when the lamp is installed in the
lamp housing.   Doesn't seem to have much spring pressure, though, so I'm
thinking I'll loop some flexible stranded copper wire around it a few times
and then likewise around the bulb socket, with enough slack to let me put
the lamp back in the housing, to boost the odds that the ground connection
will be reliable.   Check the grounds, check the grounds, check the grounds.

Dean Vinson
Saint Paris, Ohio

 

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