Advanced Marine Electrics and Electronics Troubleshooting A Manual for Boatowners and Marine Technicians

58 electrical systems troubleshooting

MAKING SURETEST ADAPTERS

It’s relatively easy to make adapters to use the SureTest to check 240 V, 50 amp shore-power service.

You will need to buy two 50 amp replacement plug assemblies (male plugs) and two 15 amp female

plug assemblies to plug the SureTest into. You’ll also need about 2 feet of four-wire 240 V, 50 amp

shore cord or the equivalent.

You need to make two assemblies so you can test the ground, neutral, and 120 V “hot” lead for

each leg of the 240 V system. Construct one assembly (B) so that the hot lead connects to the L2 ter-

minal (see the illustration) and the grounds (green or GR) and the W (white) terminals connect to the

240 V plug. Construct the other adapter (A) the same way, except connect the hot lead from the

15 amp plug’s small-bladed terminal to the 240 amp plug’s L1 terminal.

Use about 1 foot of the shore-power cabling for each adapter. Mark the L1 and L2 connections

with an indelible marker for future reference. The illustration shows how the completed adapters

should look.

A

B

black, L1

50 amp, 240 V plug

assemblies

standard 15 amp plug

assemblies

white

gray, not connected

gray, L1,

not connected

white = neutral

black, L2, connected

green

gray

black

green

black = "hot"

gray = neutral

The L1 and L2 conductors and the neutrals and grounds. In A, L1 in the 50 amp plug is activated from the

15 amp assembly. Both white terminals are activated, and both green terminals are activated as grounds. In B, the

black terminal in the 50 amp plug is the L-shaped prong, which becomes L2, and is connected to the black

terminal on the 15 amp plug. The white and green terminals are continuous.