96 Dakota wipers have me Stumped!

[78clubcab]

I just purchased a very nice 96 Dakota regular Cab short bed 4x4 3.9 auto. The person I bought it from threw in lots of extra parts, both new and old. One item he included was a new wiper motor because the wipers didn't work.

Upon inspecting the wiper problem, I discovered the pigtail that plugs into the wiper motor was slightly melted into the plug in on the wiper motor. The wire whip behind the pigtail also showed signs of getting hot. I cut a good whip and pigtail from an identical parts Dakota and installed the new wiper motor and pigtail.

I check the fuse which was amazingly not blown, and hooked up the negative on the battery. I turned on the wiper switch and.....Nothing. I pushed the wiper washer and the washer motor works. according to the owners manual the washer/wipers are one fuse.

Next, I pulled out my multimeter, and unplugged the wiper motor to check the pigtail for power. I have a constant 12v one one leg of the four . another leg shows 12v when the delay is turned on. Another leg shows 12v on low speed, and the 4th shows 12v on high speed. I would assume the wiper switch on the column is good based on this, as the pigtail was long enough for me to watch these tests in "real time" as I turned the wiper switch.

I then unhooked the wiper linkage in case it might have been bound up, but still nothing. All I can think of at this time is the new wiper motor said "made in China" on the back of it.

I am not very good with electrical and I just bought the multimeter. Is there a way to test the motor? I tried the continuity test function on the meter to all four legs of the motor plug but got no positive result but I am not sure that would work anyway. Any suggestions?

[Gordon Maney]

You may not think you are very good with electrical work, but based upon your comments I would say you are doing quite well.

Is this wiper motor grounded as a result of how it is mounted?

I have no wiring diagram here. I am uncertain as to why there might be a continuously hot lead such as you describe. You might try jumping 12 V to the terminal you believe is for high-speed, and also a jumper lead from a ground on the wiper motor to the negative terminal of the battery.

Does your parts Dakota have a wiper motor on it?

[78clubcab]

Hey Gordon, thanks for the reply. I was wondering about the ground for the wiper motor as well. The motor is mounted to a plate on the firewall but the plate is mounted to rubber washers.

I think I may try to run an independent ground to the wiper motor. I know this sounds like I am throwing parts at a problem, and I kind of think I am, but it would only take about 20 minutes and no parts cost. I think the wiring should be correct as I wired the good pigtail in exactly the way the old one came out.

The continuous hot lead has me thinking, too, though. When I used my multi meter to test the pigtail, I stuck the negative prong of the meter to the battery ground. I just kind of nestled it in so it would stay and that way I still had 2 hands to work with. Maybe I shouldn't have done that. This is the first time in my life I have used a multimeter, and I just bought it for this project.

After work today I am going to try the independent ground. My thinking is that if there is power at the pigtail the motor should work when plugged in unless: the motor is faulty; or the is a grounding issue. But again, honestly, this is at the edge of my automotive electrical knowledge.

[78clubcab]

Hey Gordon, I got it! I ran a jumper cable from the ground post on the battery to the mount on the wiper motor and the motor started to run. You were correct in assuming the motor picked up a ground through the mount. However, as often happens, the ground became corroded.

I tried cleaning up the ground twice with no luck, so I ran an independent ground to the firewall. Now the wiper motor runs fine and does everything the switch is telling it to do.

I have been thinking about the constant 12v power on one of the legs to the wiper motor. Either I was using the multimeter wrong, or maybe there is a relay in the motor that requires constant 12v power for the delay setting? Kind of like a relay for fog lights that only come on if low beam headlights are on, but go out when high beams activate. Just a wild guess. More likely I was using the meter wrong. Anyway, thanks for getting me thinking and therefore solving the problem! Now for the heater controls.........

[Gordon Maney]

I am going to scold you for one thing only: stop being so hard on yourself with regard to your multimeter skills. You did just fine — really!

When I had mentioned something about the wiring diagram, that might have explained how a constant source of battery voltage to the motor could be useful. That would explain the terminal that was always hot.

You did a great and thoughtful job in diagnosing the problem. You also did a very nice job in describing it all to us.

Congratulations… Great work! Your experience will be very thought-provoking to others as they approach similar situations.