Wiper Motor-Intermittent Operaton

[JohnnyPopper]

Few months ago my motor froze mid travel, then worked, then stopped.

If I manually move the wiper, it will go back to it's resting place with the switch off.

No fuse issue, just acts like there isn't enough voltage to move consistently.

Seem like if they are going to fail, they just do, and don't act like this.

Strange thing is that it will stop in the same spot...

[bd]

What year/model truck?  Round or square motor?  Have you measured the voltage at the motor?  How about the voltage at the wiper switch?

[JohnnyPopper]

'78 K10, think it's round, will look later, raining cats and dogs in SoCal...

Have not checked voltage, but probably the culprit.

Thought about running a 14 ga. from the battery and installing a relay.

[bd]

IIRC, the round motors used carbon brushes.  Begin by cleaning/burnishing the connections to the motor and the switch.  Make sure the wire terminals have adequate tension to ensure good contact with the motor and switch terminals.  The wiper system used Pak-Con terminals that are notorious for developing connection problems as they age.  You may need to replace the motor pigtails.  Check the voltage at the wiper motor and at the ground terminal of the wiper switch with the wipers turned on. 

Keep in mind that the motor receives constant B+ and is controlled by switching the motor's connection to ground through the dash switch.  If the motor B+ feed (yel/blk) measures full system voltage while the wiper is operating and the respective high- and low-speed wires connecting to the dash switch measure zero (when on HIGH speed the light blue wire should measure zero and when on LOW speed the black/white wire should measure zero; the black ground wire should measure zero under all circumstances), then the motor may be simply worn out.  On the other hand, if either of the switched control wires exhibit voltage >0.5 volt, there is excessive resistance lurking in the control wiring.  If the solid black wire measures greater than zero at any time, its connection to the cabin sheet metal is compromised or the cab is not properly grounded to B-.  Any connection issue(s) will starve the wiper motor of the power it needs to function.