Any mods to the truck?

 

Trucks bone stock, no mods!

 

Would it be worth a try just swapping that relay with another of the same part number in the fuse box just to rule out a the relay as being bad? Just a thought, since relays are hard to test. You have ruled out the motor and the switch.

 

What engine do you have? There are two ground locations for the wiper system. One is in the drivers side front lower wheel well just to the right of the honeycomb fender reinforcement. You may have to pull back the felt fender liner to see it. The other is under the drivers seat right next to the front seat mounting point just inside the door opening under the seat, if you want to check them.

 

How could it be a ground problem? That would result in too little current, not too much current.

 

I actually just swapped the relays the other day to try this but I’m not sure if it made any difference because I didn’t run the wipers for long after I made the swap.

Also I have the 6cyl gas

 

Does the wiper linkage move freely? Sometimes the shafts that the arms go on seize up. Take the motor out or disconnect it from the linkage and see if you can move the wipers by hand easily.
Try some WD40 on the pivots and shafts if they bind up.

 

How much you want to bet it's the fuse block itself?

 

What makes you say that? Is that a known issue with these trucks? I find it weird that it’s only this one particular fuse blowing, so I’m not ruling anything out.

 

Have you downloaded the wiring diagram, here is one place to do so:

GM UPFITTER - Body Builder Manuals

Welcome to GM Upfitter Integration - Body Builder Manuals. The ...

www.gmupfitter.com

This is a text searchable PDF.

Also, appears there are two relays involved with wiper operation, per both the wiring diagrams and the owner's manual fuse/relay diagram.

From the diagrams, there does appear to be 2 grounds, but I think a faulty ground would not be a normal cause of a blown fuse in this circuit. Also, haven't heard of faulty grounds being a major issue on 2nd Gen Twins, as opposed to the 1st Gen ground problems. But then, haven't heard of blown fuses on wipers on the 2nd Gen trucks either.

If the linkages are not the issue, then I would be checking for a shorted limit switch on the up & down positions of the wipers.

Frankly, I find that my windshield at highway speeds does not need the wipers very often, I am not sure I have ever run my wipers for 10 minutes straight, usually I put them on the intermittent setting.

Please report back what you find!

 

Have you downloaded the wiring diagram, here is one place to do so:

GM UPFITTER - Body Builder Manuals

Welcome to GM Upfitter Integration - Body Builder Manuals. The ...

www.gmupfitter.com

This is a text searchable PDF.

Also, appears there are two relays involved with wiper operation, per both the wiring diagrams and the owner's manual fuse/relay diagram.

From the diagrams, there does appear to be 2 grounds, but I think a faulty ground would not be a normal cause of a blown fuse in this circuit. Also, haven't heard of faulty grounds being a major issue on 2nd Gen Twins, as opposed to the 1st Gen ground problems. But then, haven't heard of blown fuses on wipers on the 2nd Gen trucks either.

If the linkages are not the issue, then I would be checking for a shorted limit switch on the up & down positions of the wipers.

Frankly, I find that my windshield at highway speeds does not need the wipers very often, I am not sure I have ever run my wipers for 10 minutes straight, usually I put them on the intermittent setting.

Please report back what you find!

Ok thanks for the tip, I’m gonna look into these diagrams a bit more closely. I believe the wipers ground out at the battery and under the drivers seat if I remember correctly but the grounds seemed to be in tact.

I also don’t run the wipers on higher than intermittent typically but I live in the north east and we get snowstorms and a lot of rain and it really can get dangerous when these wipers decide to blow in the middle of a blizzard or heavy rain storm =\

 

Never heard that issue with the trucks yet? Unless this is a first?

 

I ran into a problem with the wiring harness that feeds the O2 sensor circuit beneath this block. After a month back and forth to the dealer under Certified warranty, new ECM, two new O2 sensors, that THEY said were bad, I found an intermittent open at a splice that splits between the two O2 sensor 1 heaters. Ran a new wire, problem solved. The fuse block itself MUST have some inter-connectivity molded into it, which can possibly go bad and is NOT serviceable.

 

Inside the fuse box!

 

MOST EXCELLENT!

 

The couple of times in my life I have had repeatedly blowing fuses it was a short where insulation was worn off, broken, etc. On a wire and wire rubbed frame or chassis.

Not saying there can't be other issues.

 

I think resister packs have been a problem. Get some rain x till you figure it out.

 

Ya, only two wires to the motor, not likely a short to ground or together, I would guess in/under that fuse block too. Look real close and you might find some signs of high heat (melting)
As for relays, not likely, they like to fail open or close, not shorted to ground.

 

That’s the dedicated connector number, which is used for lookup on schematics and locations. The “G” is the ground connector. A loose ground can cause high resistance and heat in the circuit also which could cause the fuse to blow.

 

Guys thanks so much for all the replies. The fuse doesn’t typically blow when it’s on intermittent. When I was reading the wiring schematic it seems like the power is distributed differently when the switch is on intermittent versus a speed setting. Maybe that could have something to do with it? It seems like The BCM controls that function in the fuse block.

As for the block itself I’m wondering if that could truly be an issue. You guys are definitely making me lean in that direction. I’m gonna take a better look at the fuse block again tomorrow maybe I’ll unbolt it and see if I notice any melting or things like that on the underside.

 

Guys thanks so much for all the replies. The fuse doesn’t typically blow when it’s on intermittent. When I was reading the wiring schematic it seems like the power is distributed differently when the switch is on intermittent versus a speed setting.

I'm unclear from that schematic what that difference is--again I'm not that good at reading those things. I can see the two speeds, but can't figure out the intermittent route of power.

But, the other possibility is that simply running the motor part time is putting less draw on the circuit and not causing the fuse to blow. That would support the theory that it's the wiper mechanism that is messed up/needs lubrication.

 

@$teve
[/QUOTE]

It says in the schematic that the BCM is removable and made up of relays K4 and K5. So if the BCM is removable then would the problem still possibly be within the fuse box and not the relays themselves?
[/QUOTE]

Do you mean X4 and X5? It's hard to see that pic right?! Those switches are inside the BCM, they send the signal to the relays in the fuse block. I think you must be referring to the connectors at pin numbers is all.
Looks like there are 3 wires, a high speed off one relay(inside the fuse box), low speed of the other relay(also in the fuse box), one more is from the BCM that is probably for intermittent and maybe parking of the arms.

 

Do you mean X4 and X5? It's hard to see that pic right?! Those switches are inside the BCM, they send the signal to the relays in the fuse block. I think you must be referring to the connectors at pin numbers is all.
Looks like there are 3 wires, a high speed off one relay(inside the fuse box), low speed of the other relay(also in the fuse box), one more is from the BCM that is probably for intermittent and maybe parking of the arms.

Yes In the schematic X4 and X5 but in my fuse box they are labeled as K4 and K5

 

Got a shot of the second ground in the front fender. Again wires all seem in place and ground looks okay to me. To me the only other 2 things that I can think of are bad relays or a bad fuse box? What do you guys think?

 

Well, if it only does it on high for example, you could swap the relays and try it. I bet it's the fuse box.

 

There is no difference in your 2015 and any other 2015. The parts are the same. In the old days maybe there were pre production parts released but not anymore.

 

Did you ever figure this out? Going through this exact issue right now