What is this electrical device?

[Kens1990K2500]

Hi,
I am getting ready to replace my front driver's side inner fender/wheelwell, and I noticed some unusual wiring mounted on the wheelwell, next to the washer fluid reservoir. I'm going to have to remove it to replace the wheelwell, and since it's so corroded, I'm going to replace it, when I install the new wheelwell.

Trouble is, I'm not quite sure what it (I'm referring to the fourth photo from the left) is. My best guess is that it's just an electrical junction block. My second guess is that it's a fusible link. It doesn't appear to be stock, but something that was added on.

There is a wire that comes out of the firewall, and goes under the truck somewhere. It appears that the jacket to this wire was split (you can see the white conductor, likely a neutral), in order to tap another black wire into the circuit. There is a small, black jumper wire between the two blocks. The wire that is tapped into this circuit is spliced into a wire that comes out the back of the alternator (see third photo from left).

I'm thinking that the alternator is feeding power to these two junction blocks, which are tied together with a jumper, and then feeding power to something in the cab, and something under the truck. I haven't investigated where those two wires terminate, nor do I care at this point. Like I said, I just want to replace this part on my wheelwell.

Does my analysis sound correct? And if it is simply a junction block, there's got to be a better (cleaner) way of joining these wires.

 

[texas tough]

they are circuit breakers ,, trace the wires and see wher they go,, maybe an aftermarket lightbar, hooga horn, ect. not sure why someone would splice something in directly to the alternator.. I would get rid of all of that crap.. these trucks barely generate enough amps to run what the truck comes with stock., adding high amp draw add ons , is usually problematic.. those circuit breakers are self resetting, and they put two in series to try and handle whatever fukery they were trying to accomplish,,

 

[GMCTruck]

Possibly for a trailer brake controller

 

[Kens1990K2500]

they are circuit breakers ,, trace the wires and see wher they go,, maybe an aftermarket lightbar, hooga horn, ect.

When you say circuit breakers, are you implying that the are re-settable, in case of short-circuit, or over-currrent? I don't see any way to re-set these, but then again, they are so corroded.

Or are they a one-time current protection advice, that breaks the circuit in case of a short or excessive current? That is what I would describe as a fusible link.

Just want to make sure we're on the same page.

 

[Kens1990K2500]

Possibly for a trailer brake controller

Interesting, because the original owner did tow a camper with it, I was told. It must have been a fairly big camper too, because the truck had a fifth-wheel type hitch in the bed (which was removed). If there was a brake controller, that was removed too. Now you've made me curious enough to crawl under the truck and peek under the dashboard to see where those wires terminate.

If I find they no longer go to anything, then I can just eliminate that mess and cap off the wire from the alternator.

 

[Scooterwrench]

Yeah,those circuit breakers reset themselves. They work with a bi-metal strip inside. When the current exceeds the rating for the CB that strip gets hot and causes it to pop open. when the strip cools it will pop closed. Normally takes 15-30 sec. to reset depending on how violently it popped.

 

[pressureangle]

Trailer stuff. It isn't clear how many wires are there, but it would be common practice to use one 30A circuit breaker for the brake controller, and on a big camper another 30A breaker on the power feed (accessory) line, to charge the batteries/power the trailer from the tow vehicle's alternator.

 

[Kens1990K2500]

Okay, I did some poking around, tracing wires. Yes, it appears the wiring was for a brake controller. In the cab, there are two disconnected wires, taped under the hood release.

Under the truck, the wire runs along the frame rail, until it is spliced into the factory wire harness, aft of the gas tank. The black conductor has been cut off. The white wire goes into another wiring harness that splits off the main one. That branch wiring harness goes over the top of the frame rail, and then it goes up into one of the bed supports, which seems very odd to me (not sure where it goes from there). I don't think the factory would have routed it like that, but maybe it had something to do with the fifth wheel hitch that used to be in the bed? I should have pulled on it, to see if it pulled out and was dead-ended and stuffed up there to keep it from dangling.

In any event, I will have to deal with it when I pull my bed, along with the broken ground strap you can see next to it.

So, it appears I can safely get rid of those circuit breakers and the wiring that goes into the cab, and along the frame rail, since the accessories it served have been removed. I don't anticipate towing any large trailers in the future (just maybe a small, uncovered motorcycle trailer, which I don't think needs a brake controller). In any event, the wire was ran sloppily, and I will likely be replacing the brake and fuel lines along the frame, and cleaning up the frame.

What should I do with the wire that comes off the alternator? It appears to be spliced into a wire off the back of the alternator. Who knows how well that splice was done. If it was poorly done, I should remove it, but if it's a decent splice, could I just 'cap off' the end of the wire for possible future use?

 

[dave s]

I'm no expert but I would eliminate it back to the splice at the alternator.

 

[Grogu]

Hi,
I am getting ready to replace my front driver's side inner fender/wheelwell, and I noticed some unusual wiring mounted on the wheelwell, next to the washer fluid reservoir. I'm going to have to remove it to replace the wheelwell, and since it's so corroded, I'm going to replace it, when I install the new wheelwell.

Trouble is, I'm not quite sure what it (I'm referring to the fourth photo from the left) is. My best guess is that it's just an electrical junction block. My second guess is that it's a fusible link. It doesn't appear to be stock, but something that was added on.

There is a wire that comes out of the firewall, and goes under the truck somewhere. It appears that the jacket to this wire was split (you can see the white conductor, likely a neutral), in order to tap another black wire into the circuit. There is a small, black jumper wire between the two blocks. The wire that is tapped into this circuit is spliced into a wire that comes out the back of the alternator (see third photo from left).

I'm thinking that the alternator is feeding power to these two junction blocks, which are tied together with a jumper, and then feeding power to something in the cab, and something under the truck. I haven't investigated where those two wires terminate, nor do I care at this point. Like I said, I just want to replace this part on my wheelwell.

Does my analysis sound correct? And if it is simply a junction block, there's got to be a better (cleaner) way of joining these wires.

If plan on replacing it I would find out what it is first. But it kind of looks like a positive Junction box. But to see if that is true test with an ohm tester to find out if any juice is going through there