Still blowing fuses

[milesengineer]

Had issues earlier with the ty and thought a new battery/starter/purple wire & alternator fixed it. Today it came back and stranded me. The original owner did a lot of bs wiring hackery and I am still trying to sort it.
First off, one of the original fusible links on the back of the alternator is gone and in its place is an inline fuse. Twice now the fuse has gotten so hot it actually melted the plastic. once with a 30 and last time with a 20amp. What i noticed the last time was the truck started acting like the power was cutting in and out once I let off the gas. As I was pulling onto my road it did it again and finally stalled. Got it home and started working on it. First thing I did was put a new fuse in the holder. Most things worked but some were still MIA, headlights and interior lights. Checked the fuse block and had a couple fuses popped, think it was the gauges and horn fuse. Popped them in and started the truck. Ran fine. Checked the fuse and it was cool to the touch. Turned the lights and A/C on and the damn thing popped almost immediately. Started disconnecting things, first was the efan and lights. Did the same startup procedure and the fuse got warm but not hot. Started plugging lights back in and the fuse started warming up. With all the lights plugged in and the a/c on it got hot again, but not hot enough to melt the fuse.
I dont want to burn the truck down but I am not sure where else to look. Has a bad ign switch or light switch ever caused such an issue? All the grounds I could find looked good and felt tight. Just not sure what could be putting such an amp draw on that circuit. Any help is appreciated.

 

[IpHoOnDyou]

Re: Still blowing fuses

Had issues earlier with the ty and thought a new battery/starter/purple wire & alternator fixed it. Today it came back and stranded me. The original owner did a lot of bs wiring hackery and I am still trying to sort it.
First off, one of the original fusible links on the back of the alternator is gone and in its place is an inline fuse. Twice now the fuse has gotten so hot it actually melted the plastic. once with a 30 and last time with a 20amp. What i noticed the last time was the truck started acting like the power was cutting in and out once I let off the gas. As I was pulling onto my road it did it again and finally stalled. Got it home and started working on it. First thing I did was put a new fuse in the holder. Most things worked but some were still MIA, headlights and interior lights. Checked the fuse block and had a couple fuses popped, think it was the gauges and horn fuse. Popped them in and started the truck. Ran fine. Checked the fuse and it was cool to the touch. Turned the lights and A/C on and the damn thing popped almost immediately. Started disconnecting things, first was the efan and lights. Did the same startup procedure and the fuse got warm but not hot. Started plugging lights back in and the fuse started warming up. With all the lights plugged in and the a/c on it got hot again, but not hot enough to melt the fuse.
I dont want to burn the truck down but I am not sure where else to look. Has a bad ign switch or light switch ever caused such an issue? All the grounds I could find looked good and felt tight. Just not sure what could be putting such an amp draw on that circuit. Any help is appreciated.

Sounds like you have a short somewhere or the guy who wired this before you spliced a bunch of lights a/c ect..... Into one circut

 

[RealFastV6]

Re: Still blowing fuses

Dude you can't replace a fuse link with a 30a fuse. You need to replace the fuse link before you even think about looking anywhere else.

 

[milesengineer]

Re: Still blowing fuses

forgot to add that. have replaced it twice and both times the fusible link failed the same way. got hot and the last one actually melted.

 

[RealFastV6]

Re: Still blowing fuses

How is your efan wired? Where is the 12v line to the relay coming from?

 

[milesengineer]

Re: Still blowing fuses

I have eliminated it from the equation by unplugging all power. Just have the essentials plugged in right now.

 

[BoostedSUV]

Re: Still blowing fuses

A bad ground will do what you're describing.

Also a bad fuel pump or after market pump with stock wiring will melt fuses. Been there, but it sounds like you've got a bad ground somewhere to me. That will heat things up and cause the truck to cut in and out for sure.

 

[milesengineer]

Re: Still blowing fuses

Guess I will be taking more things apart this weekend.

I was just doing some research and I have stumbled on something of interest.

The problems occur when there is a load put on the system, ie a/c and lights. IF the alt is putting out over 30 amps will it melt the fuse as it is doing?

 

[Don W.]

Re: Still blowing fuses

Dummy here has never figured out WHY a bad ground will blow a fuse. But anyway all my books are at the shop. But I just went through my truck wiring for a different reason but need those diagrams to post something meaningful. I will have some thoughts then.

Meantime, pull all the fuses. then insert them one at a time and see what blows. Nothing? Do it again with the key on. Hamburger wiring jobs drive me nuts.

 

[Don W.]

Re: Still blowing fuses

Guess I will be taking more things apart this weekend.

I was just doing some research and I have stumbled on something of interest.

The problems occur when there is a load put on the system, ie a/c and lights. IF the alt is putting out over 30 amps will it melt the fuse as it is doing?

Alternators are self limiting for amperage. They CAN, however, go wacky and make to much voltage. Simple to pull it and have it checked. But I'll bet a dollar to a donut that ain't it.

 

[BoostedSUV]

Re: Still blowing fuses

Dummy here has never figured out WHY a bad ground will blow a fuse. But anyway all my books are at the shop. But I just went through my truck wiring for a different reason but need those diagrams to post something meaningful. I will have some thoughts then.

Meantime, pull all the fuses. then insert them one at a time and see what blows. Nothing? Do it again with the key on. Hamburger wiring jobs drive me nuts.

You've never had a loose intermittent ground create a ton of heat in wires, and melt the plastic on fuses? I sure as hell have.

chances are its a short, intermittent short, or an over load on the system. I agree, I highly doubt its the alternator.

 

[Don W.]

Re: Still blowing fuses

You've never had a loose intermittent ground create a ton of heat in wires, and melt the plastic on fuses? I sure as hell have.

chances are its a short, intermittent short, or an over load on the system. I agree, I highly doubt its the alternator.

Maybe I'm nuts, or tired, it's been a very long week, but if high current, for the wire size, creates heat and a bad ground is gonna reduce current flow where does the heat come from? I'll bet what you experienced is a burnt wire AT the ground created by the high resistance of the bad ground connection itself. That I'll agree on. Bad connections will get hot, on either end.

 

[BoostedSUV]

Re: Still blowing fuses

Not saying that's necessarily the issue but I had a ground that was loose enough that when it moved it arced and blew the fuse. A poor ground will create heat but probably won't blow a fuse, a ground that's really loose with enough current draw, say the main ground to the back of the head, could infact pop the fuses if loses and regains contact.

I would definitely lean more towards current draw. There's probably something wired in that needs a relay and is pulling too much power. I had a similar issue with my elec fan when I had a relay wired wrong. The fuse box was providing the power to the fan rather than triggering the relay and the draw being against the battery or alternator. The fact that it happens when everything is tunred on made me think a bad main ground since the load is being put on the entire system.

 

[The Bronze]

Re: Still blowing fuses

but if high current, for the wire size, creates heat and a bad ground is gonna reduce current flow where does the heat come from? I'll bet what you experienced is a burnt wire AT the ground created by the high resistance of the bad ground connection itself. That I'll agree on. Bad connections will get hot, on either end.

This is 100% correct. The problem (fuse blowing) occuring is not caused by a ground, which is AFTER the load. It is caused by resistance BEFORE the load or the load itself. Resistance causes heat, which causes higher resistance, which causes more heat, which causes higher resistance, eventually insulation starts to distort/melt. If you see a melted wire at a connection, it is usually a bad connection and less a current issue.

Are you sure that the other fusible link is okay? Pull on it and make sure it isn't stretchy, which means the wires melted on the inside and the insulation is the only think keeping it connected. The two links connect at a junction. If the other link was bad, you will be trying to power much of the vehicle through a single fuse, which is way more than it was designed for. That would be a reasonable cause for excessive heat.

You need to replace the fuse with fusible link wire. The link is designed for short circuits, not normal high vehicle loads. Most likely your problem will be gone. Remember that all the ciruits powered from the links are fused further down the line. This is just to protect from shorts BEFORE the fuseblock or from real excessive loads. The correct fusible link wire will be 4 gauge sizes smaller. That is to say if the wire is a 12 gauge, buy some 16 gauge link wire and install it.

The fusebox fuses are a problem if they are blowing, and you can start chasing those down after the link wire is repaired.

 

[The Bronze]

Re: Still blowing fuses

Not saying that's necessarily the issue but I had a ground that was loose enough that when it moved it arced and blew the fuse. A poor ground will create heat but probably won't blow a fuse, a ground that's really loose with enough current draw, say the main ground to the back of the head, could infact pop the fuses if loses and regains contact.

While you may have experienced something of that nature, I don't agree with this as a typical statement. The arcing will definitely occur due to the load (current) jumping to ground, but that current is spread across all the circuits involved. The only part of the circuit that creates the current is the (low) resistance of the device (fan, pump, light, relay) itself, almost everything else (switches, fuses, grounds) actually creates higher resistance that actually impedes (lowers) the current. At the point you "arced", you actually had high resistance (the air gap is resistance) and less current than normally would be present. YMMV.

 

[milesengineer]

Re: Still blowing fuses

Bronze, you might be onto something. I never thought of checking the other link. Since they both go to the junction on the firewall I assumed it would be ok but once I checked the schematic I see they dont power separate sides of the block but are linked together. Gonna go and check that right now..


* Just checked and you are correct sir. So the problem was the truck was being powered by a 30amp fuse instead of the two fusbile links. Now I hope the local dealer has more of the links because I bought the last two they had in the size I needed. Fingers crossed this is the problem...

Thank you everyone for your ideas..

 

[RealFastV6]

Re: Still blowing fuses

The two links connect at a junction. If the other link was bad, you will be trying to power much of the vehicle through a single fuse, which is way more than it was designed for. That would be a reasonable cause for excessive heat.

Boom.

Good call.

 

[milesengineer]

Re: Still blowing fuses

Well, looks like the problem is fixed. Cleaned up a ton of bs wiring and a new vac kit as well and the ole girl seems to be on her the way to running top notch again. I dont understand people who botch things like this but spend tons of money on the shiny parts. My truck has all sorts of aftermarket stuff, just none of it is installed correctly.


thanks again...

 

[Don W.]

Re: Still blowing fuses

Tom,

With all due respect, There is no bat to alt wire with a fuesable link. Only a solid wire. On the alt there are 3 wire terminals. (The fuseable links are paired onto one terminal so 4 wires total.) One is the feed from the bat, one is the feed to the intercooler pump relay (it has its own fuse.), one (the paired fuseable links term) splits with one going to the junction block on the firewall then from there to the firewall connector (engine compartment side of the fuse panel). the other goes directly to a different terminal on that same firewall connector.

So a couple of things: I post this so that some future search that ends up here has the correct info. AND although I haven't done it to my truck I agree fully with your comment about getting those wires OFF the alternator and onto the bat. Or at least an added junction block that gets it's feed direct from the bat. Bat term on the starter being a good spot for us with bat's in the bed.

For example MSD is adamant about NOT putting their feed wire on the alt.

Sorry for the delay but wanted the book in front of me before I posted.

HTH

 

[Don W.]

Re: Still blowing fuses

Thanks i have over stayed my welcome

Wow. To bad. I was only posting info direct from the GM Syclone supplement. I've been corrected here many times and I haven't left yet. For the record I apologize if I insulted you in any way.