SPECIFICATIONS

Vehicle Systems Testing And Adjusting

Ground Test

1. Digital multimeter can also be used to test for

grounds. Put the Function/Range Switch on the

2M resistance (A) scale. When the test leads are

put on the commutator and the shaft, the meter

must give an indication of overload (OL). This

means that the resistance is more than 2

megohms.

NOTICE

Never use air pressure that is more than 205 kPa (30

psi). Make sure the air line has a water filter.

If there is an indication of a ground in the above test,

remove any dirt or debris from the armature with

compressed (pressure) air.

Do the ground test again. If there is still an indication

of a ground, replace the armature.

Open Circuit Test

1. Put the digital muitimeter Function/Range Switch

on the 200 ohm resistance (½) scale.

2. Put one test lead on one commutator bar. Put the

other test lead on an adjacent (next to) bar and

there must be less than one ohm resistance.

This test can also be done with an instrument, such

as a Kelvin Double Bridge, that can make a mea-

surement of very low resistance. Do the test the

same as above and make a comparison of the resis-

tance measurements.

Two burned areas on opposite sides of the commu-

tator are indications of an open armature winding.

These burned areas can cause very rapid brush

wear.