M1008 windshield wiper short

[mbavers]

I've got a 1985 M1008 used only for snow plowing. This winter the fuse for the wipers blew when I wasn't using them. The plow was piggy-backed off the wiper fuse, so that's how I knew the fuse blew. It happened twice and it seems the fuse blew when I turned the wheel to the left. I moved the plow connection to another fuse, but the 30 amp wiper fuse now blows as soon as I turn on the ignition. I pulled the steering wheel hoping to be able to access the wiper control wires, but I can't. Any help in troubleshooting this would be greatly appreciated. I don't know which wires go to the wiper motor. If I did I would test for a short and if the motor is not shorted out I would insall a separate switch for the wipers. I rarely use the wipers, so it doesn't have to be convenient or original equipment. Also, how do I access the wiper motor? I had trouble removing the cowl grill (between the hood and the windshield) and gave up on that.

Seems I spend all winter plowing and all summer getting ready to plow. There's got to be a better way.

 

[Barrman]

Under the column there is a huge multi wire flat plug for the blinker system. Them another with 5 wires. That 5 wire plug is the wiper system. Unplug it and see if the fuse works. If so, the problem is in the column or switch. If not, then you are still under the dash looking.

 

[mbavers]

QUOTE=Barrman;2010630]Under the column there is a huge multi wire flat plug for the blinker system. Them another with 5 wires. That 5 wire plug is the wiper system. Unplug it and see if the fuse works. If so, the problem is in the column or switch. If not, then you are still under the dash looking.[/QUOTE]

I did it and the fuse didn't blow, so I will be tracing it from there. Hopefully I can find two wires that will work the motor and install a simple switch. Thank you very much for your help!

 

[mbavers]

I spoke too soon. I had the fuse in the wrong place. There is a short to ground downstream from the wire plug. I checked all five pins, and the three center ones are all grounded. I assume the two outside are hot in and hot out? Anyway, does anyone know how/where to access the wiper motor?

 

[Barrman]

The wiper system works off of ground switching. Look at the wiring diagrams at the back of the -20. Power goes from the fuse to the motor. All the rest of the wires control the ground.

 

[rustybuttrusty]

I had the same problem before you take the whole truck apart and are screaming check the whit wire that is going from the wiper motor along the firewall it goes all the way to the fuel heater and it could be shorting there. Hope that helps.

 

[MarcusOReallyus]

Hopefully I can find two wires that will work the motor and install a simple switch. Thank you very much for your help!

Why would you want to butcher it? Find the problem and fix it and have a properly working system.

 

[mbavers]

The wiper system works off of ground switching. Look at the wiring diagrams at the back of the -20. Power goes from the fuse to the motor. All the rest of the wires control the ground.

Thanks for your reply. Hate to be such a dummy, but what is the -20? If it's a repair manual how can I get one?

I'm having trouble tracing the shorted wire. I'm thinking of just running a new hot wire to the motor, but can't figure out where. I've never seen a wiper motor like this. Seems to be the motor and washer pump unit on top, but what is the other separate-but-connected part below? It looks like it is fed electrically by three connected cylinders, each about 3/4" D X 1 1/4" long, look like capacitors. As you can tell, I don't know what I am doing. Any help much appreciated.

 

[mbavers]

I had the same problem before you take the whole truck apart and are screaming check the whit wire that is going from the wiper motor along the firewall it goes all the way to the fuel heater and it could be shorting there. Hope that helps.

Don't see the wire you mentioned. Didn't know I had a fuel heater.

 

[mbavers]

Why would you want to butcher it? Find the problem and fix it and have a properly working system.

I understand how you feel about keeping things original, but I'm an old guy and not so spry anymore. Also have a backhoe and dump truck to get fixed. Since the truck is only used for plowing, I would be happy with a simple system, one wiper speed would be OK, and do not need the washer. (I also replaced the original fuel with an electric one, so never have to bleed the hoses if any air gets in.)

 

[rustybuttrusty]

Yup these do have fuel heaters unless yours isn't oem and an aftermarket base. If you check the wiring diagram it is on there. I could try to get you pictures later.

 

[MarcusOReallyus]

Thanks for your reply. Hate to be such a dummy, but what is the -20? If it's a repair manual how can I get one?

Beg. Plead. Grovel. Or, just download it for free from this site. Click right here.

The -10 is the operator's manual. The -20 is the unit repair manual. The -20P is the parts manual. Get 'em while they're hot!

I'm having trouble tracing the shorted wire. I'm thinking of just running a new hot wire to the motor, but can't figure out where.

Then don't! That's what the -20 is for. Wiring diagrams! You can also find wiring diagrams in the Helpful Threads sticky.

I've never seen a wiper motor like this. Seems to be the motor and washer pump unit on top, but what is the other separate-but-connected part below? It looks like it is fed electrically by three connected cylinders, each about 3/4" D X 1 1/4" long, look like capacitors.

That's what they are. One of the differences between the civilian version of this truck and the military version is the proliferation of capacitors and diodes on the military version, that are intended to suppress radio noise. These things are known troublemakers, and many of us just remove them. More info here.

As you can tell, I don't know what I am doing. Any help much appreciated.

That's refreshing! A man who is man enough to admit he doesn't know everything!

 

[mbavers]

I finally located and replaced that white wire, which was bare in places, and cleaned a very dirty plug at the fuel heater end and that was the problem! I never would have found it on my own and very much appreciate the tip.....THANK YOU.

 

[mbavers]

I had the same problem before you take the whole truck apart and are screaming check the whit wire that is going from the wiper motor along the firewall it goes all the way to the fuel heater and it could be shorting there. Hope that helps.

I finally traced the white wire. It had bare spots and the plug end was very dirty. Replaced the wire, cleaned the plug, and that was it; works great now. I never would have found this without your help....THANK YOU!

 

[mbavers]

Thank you all for your attention to my problem!