I am trying to get my 1990 F150 going and on the road again. It had a few problems that needed fixing, which is why I quit running it. One of them is no windshield wipers. For a long time they would run for awhile then suddenly just stop mid stroke and do nothing. If I would turn the switch off and wait a few minutes I could start them and they would work. The longer I waited the longer they would run before quitting. They would run longer before stopping on low speed than on high. This all lead me to believe my wiper motor was shot. I got a used wiper motor off of another 1990 F150 parts truck that I have and it doesn't run at all. (neither does my original motor, it quit awhile ago) So with either motor hooked up I hear a clicking every few seconds from behind the dash in the instrument cluster area but that's it, no motor running. I looked in the fuse block for a self resetting curcuit breaker but since this thing was made by Ford there are none....wouldn't want to make it too easy to fix you know. Do I have 2 bad wiper motors or is something else wrong?
See if you have 4 wires going to the wiper motor. When in LOW, you should have voltage on the white wire and the red wire. You might have a pulsing voltage on the white wire if you have the intermittent delay on. In HIGH you should have voltage on the darkblue/orange and still have it on the red. All these voltage readings are with one of the testlight or voltmeter probes on ground.
If you have voltage, but it still won't run, check your grounding of the motor. You could also take a battery charger and hook it up to see if the motor will run on the bench.
I have 2 plugs on this motor. When I unplug the wiper motor the clicking under the dash stops and I have 12v+ on the red wire of the black plug. One of the other wires on the black plug is 12v- but it never changes. Doesn't change what my test light does on any wire no matter what I do with the switch. When the motor is hooked up and the clicking is going on under the dash My test light shows 12v+ on the red wire, but it goes on then off every second or two in perfect time with the clicking under the dash.
How about this question. One plug must be 12v+ on one wire, then the other two would be for low speed and high speed 12v-. Is this correct, and what is the other plug for?