Where to start when wipers won't start?

[92Jalopy]

'92 Explorer... windshield wipers won't start working until the vehicle has been running for about 10 or 15 minutes. It may be temperature related, seems to be more likely when it's in the 40s but it's always in the 40s in Seattle in the winter. Once the wipers make one complete slow trip across, everything works fine - high, low, intermittent no problem, no sluggishness.

I've tried every setting and combination of turning them off/on, etc, as well as tugging a bit at the wipers and making sure they're not caught on the glass. When it is trying to get going, the voltage dips a bit (down to 12V) when the intermittent would be kicking in. Revving it or turning on/off anything electric has no effect.

I know some possibilities, motor or multifunction switch or wires. I would really appreciate anyone who might recognize the symptoms without my spending too much on dead ends.
Thanks,
Tim

 

[dzjammer]

You may want to check the ground going to the wiper motor. Its under the hood and fairly out in the open. make sure its there and tight or make a jumper wire to ground to something solid and see if it makes a difference

 

[boggs1227]

yeah i would check the ground going to the motor ,if it works ever so slightlly when you say it warms up then the heat in the engine compartment could be expanding the metal to make a faulty ground grab better so to speak .if its a bad ground then the metal heats up expanding the groundpoint to make a better connection electrically speaking ,id either redo the ground wire or take it off and retighting it with a new star-lug type locking washer.but make sure if you end up takeing it off to scuff up the area it bolts into with a piece of sandpaper or a wire brush to expose freash metal.

hope this helps

 

[Anime]

Sounds like the motor isn't getting much power at first, then once it does, it stays that way. I'd agree with checking the ground and the wiper motor wires, plus be sure to check the wiper relay, replace with a spare or swap with one just to test. With all the rain in Seattle, it might even be that the motor is plain worn out.

 

[92Jalopy]

Hi y'all. I've kinda fallen off the face of the Internet for a while. I appreciate your responses and especially the explanations. I did the easy and cheap thing, removing, scuffing and tightening the ground wire. It has pretty much solved the problem. There have been just a few times since then (last spring) where the first swipe was slow but nothing as bad as before. All of the wires looked/felt good; I will keep the relay-replacement in mind if it ever messes up again.

Thank you all, especially for NOT suggesting: new battery, new wiring harnesses, new wiper motors!