blowing wiper fuses like crazy 74 FJ40 (1 Viewer)

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Jun 27, 2011
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ok.. need some assistance here.. I'm blowing my wiper fuses like crazy. I have a 74 FJ40 and wipers weren't working. I went down and check the fuse and it was blown.. no key in ignition, popped in a new 20a fuse turned key but didn't start car fuse blew... this happened about 3 times.. ??

I have removed the wiper washer bottle resovior and pump from under the hood b/c it wasn't working.. by removing that could I be causing a short in the line?

not sure what to check here.. everything else electrical is working just fine with no issues at all.

Thanks for the help.

John
 
Agree that you have a short or grounding issue.

I don't think an inoperable washer pump would cause the fuse to blow. When I got my '74 it had no reservoir/pump at all but the wipers worked.
 
thanks for the tips.. I'll check all that was mentioned.. I know after taking out the wiper fluid piece the plug that's left is female I believe, so I'm thinking that's not it, but you never know.

and yes this just started happening after I pulled the wiper washer motor.. and I think prolly after I went to power steering.... ugh

I'll check the wires through the firewall and maybe I can backtrack it to the button to. I'll let ya'll know what I find.

Thanks!
 
Wipers are pretty complicated. If you're blowing a 20a fuse with the ignition off you may have a short in the motor. It would be easy enough to measure the resistance between the non-powered side of the fuse and ground, then unplug the motor and see if it changes. That will save you continuing to blow fuses to test it. With the motor unplugged there should be infinite resistance to ground. If you get some low number of ohms, you have a short.

To debug a short in the parking circuit of the motor, check out these threads:

https://forum.ih8mud.com/40-55-series-tech/698941-windshield-wiper-return-question.html
https://forum.ih8mud.com/40-55-series-tech/439669-weird-wipers-76-fj40.html
 
thanks, I'll take a look.. ok it's only blowing when the ignition is turned on.. I blew 3 more today trying to trouble shoot it.. I even pulled out my radio and cage to look up in there too.

so I'll put in a new fuse, put in the key turn the ignition almost to start and it will blow.. I noticed two times that when I put in a new fuse, turned the ignition almost on and nothing.. turned on wipers.. nothing. .went down to the fuse box and pushed the fuse back a for a bit in it's holder and it popped...

All the wiring seems ok that I can tell.. all other electrical works just fine.. lights, side markers, fans, horn, gauges, hazards.. all ok.. just the wipes do nothing... I'm almost tempted to plug back in the wiper motor, but I know that probably won't make a difference.

Any ideas?
 
You are wasting fuses by putting a new one in each time without finding the fault first. You need a multi-meter and test the cables to see where it is shorting out. Disconnect your battery, unbolt the fusebox and check at the back of there too. Test your wires to ground/Earth on the body. Are your wires in good condition or blackened from over-heating?
 
I was having a short issue with my wipers on the slow speed.

The wiper would work on full and shut off okay, but if you stopped in the middle for more than a second, it would blow the fuse.

On accident, I discovered (after knocking the little black cover off and destroying it) that the blue wire with the black stripe in this pic was chaffed and grounding out on the corner of the switch. It also needed to be re-soldered to the small tab to the left.

May want to CAREFULLY remove that little cover and check these connections.

I fixed it and it cured my fuse blowing issue.

Hope this helps.


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thanks for that.. good to know.. I printed out the wiring schematics really big for me to look over and see if I can trace this out..

always good to check something I didn't think about.

Thanks!
 
hey guys,

I started thinking about this some more.. so what it I removed the old wiper fluid assembly, I basically just unbolted it and unplugged it from the pump and took it out.

i know it's part of the wiper system, but didn't think anything about it, guess I did it a while before I decided to try the wipers...

Would removing that cause the fuse to keep blowing?

I'm going to hook it back up when I get a chance and see.. I'm so hoping that's what did it...

Schlosser
 
You need a meter or you need to build this simple device to help when dealing with a short. Take a park light or similar single element +12V bulb. Solder one 12" long wire to the bulb base (ground) and another 12" long wire to the bulb tip. Attach alligator clips to the ends. Now remove the wiper fuse and clip the two alligator clips to the empty fuse clips. Turn on the key to run position. If there is a short, to ground, the bulb will light AND LIMIT THE CURRENT THROUGH THE SHORT TO ABOUT 1 AMP!!! You can now safely work on this circuit without melting something.

Starting at the wiper switch, wiggle wires while watching the bulb. If it flickers or goes out you have found the location of the short. Follow the wiper wires to where they go up into the windshield frame, then through the frame across the top to where the 4 pin plug is. Unplug the 4 pin plug. If the bulb goes out the problem is somewhere in motor or the park switch.

Note: do NOT leave the key on for a long period of time. You can burn up your points, a coil, or the igniter depending on what you have.
 
Hi,

you guys were right, needed to get a volt meter. Grabbed one from my dad and he helped me work through it and isolate the short.

We disconnect the plug at the wiper on the windshield
tested each plug and found the one that had a short
followed it down to the fuse box and checked it there
grabbed a wiring diagram and found is was the just the 12v lead that didn't go to the wiper switch
cut the wire on the back of the fuse box and connected it up the line that went to the wiper switch
I didn't take apart the rats nest of wires to try and find it.
The radio which used to share that comes from another line and the wiper washer I need to replace
so I think I'll add the wiper washer back and spline into the wires I afixed togther.

Thanks so much for the help.
 

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