diesel cowboy

Hi all, Been a while since I posted. Need a little help with the windshield wipers on my 93 W250. Just finished putting it back together after a 2 1/2 year rebuild and now the wipers wouldn't turn on. They were working fine in the rain on my drive into work the other day and about 3 hours later I went to move the truck and it had about a half inch of snow on it. Hit the switch for the wipers and they didn't move. The blinkers, washers, and high beam switch still work. Thought it was probably the ground as I've had that happen several times over the years to different trucks, but that didn't work so I check the fuse and thats still good. A test light shows power on both sides of the fuse.

I have a factory manual and have tested the motor and switch like it says. Put an ohm meter on the switch and it makes a circuit at the terminals as you turn the switch. Tested the motor and there's power going to it and with the multi-meter hooked to the L wire and the mounting bolt it shows 12.19V, moving the ground probe to the battery shows 12.26V. I pulled the motor off and put it on the bench to test it. Hooked jumper wires up to the 2 wires that run the motor and it works fine, switch the wires and it still works just backwards. Put it back on the truck and still nothing.

From what I understood from reading the manual I'm looking at a bad wiper motor but before I go spend $50 on a new one I figured I'd ask and see if I'm on the right track or if I might've missed something. Thanks in advance, Stewart

edwinsmith

Mine stopped working and I found that the ground was open. There is a small piece of copper foil running around one of the rubber grommets to make a ground. Check that and make sure it's clean. You can tell if you have a bad ground by putting your meter on the case of the wiper motor and the other lead on a good ground. When you turn on the wipers if the meter shows 12V then you have a bad ground.

Edwin

diesel cowboy

I just went and tried that with the negative lead right to the battery and then to a bolt next to the radiator and the meter showed 0.126v with the switch in off, low, and high. Just for laughs I switched it over to ohms and checked and it has continuity from the motor itself all the way up random points on the firewall and fender to the battery so I'm pretty sure the ground is still there

diesel cowboy

Just an update. I headed out earlier to do some shopping and out of habit pushed the button for the washers and the wipers work now in all speeds. Guess I got a loose wire somewhere. Glad there working for now but I'd really rather have to change a burned out motor or switch than chase electrical gremlins

edwinsmith

Welcome to gremlin central. These old trucks have plenty. I would be ready to bet you have an intermittent ground problem on that motor. You hit a bump and it will start/stop working.

Edwin

diesel cowboy

Guess I'm one of the lucky ones and there's only been three gremlins that have popped up over the years. My great uncle bought it new then gave it to my cousin a few years later and then I ended up with it in about 06. The only thing that went wrong when they had it was the fuel gauge stopped working and since I've had it the charging circuit in the "computer" went bad and now this.

The only thing about it maybe having an intermittent ground issue that's throwing me is the fact that when it first happened, I put a jumper wire from the wiper motor right to the negative terminal on the battery and it didn't work. I know when I put the truck back together I didn't get all the original ground straps put back on so maybe that's part of the problem?

edwinsmith

My wipers would only work on high speed when I first got the truck. I finally figured out that there was a broken springy terminal in the plug for the intermittent wiper module. The module was fine however. I couldn't fix the plug so I cut it off and soldered the wires to the module and it's been working fine ever since. The lesson: Don't assume a circuit is good just because you got voltage at the plug because the plug could be bad and not making contact.

Edwin

thrashingcows

I had a similar issue with my reverse light switch. Using the digital multi-meter it was showing the switch was good but I was not getting any reverse lights. So traced wires and check continuity, and replaced bulbs and bulb sockets...everything said it should be working. I finally decided to hook up an actual test light and the switch would not turn on the lamp.....so finally figured out I needed a new switch since I guess under actual "load" the switch would fail.