Fusible Link Issues
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Trailering
Joined: Dec 2022
Posts: 15
Likes: 1
Fusible Link Issues
Evening All,
Looking for support regarding issue of the fusible link burning up. I cant aeem to isolate the cause. Seems to happen when either using the turn signals (signal stalls and I have to fiddle with it and it engages again) or when I hit the highway and run 60-65mph.
Ive installed a fuse disconnect with a 30 amp replaceable fuse to save the link from continuing to burn up. Replaced the voltage regulator recently and still burning fuses. Is this a bad alternator or a short some place?
Thanks in advance for your help.
Jon1977 F350 Ranger XLT Camper Special 460/C6
Looking for support regarding issue of the fusible link burning up. I cant aeem to isolate the cause. Seems to happen when either using the turn signals (signal stalls and I have to fiddle with it and it engages again) or when I hit the highway and run 60-65mph.
Ive installed a fuse disconnect with a 30 amp replaceable fuse to save the link from continuing to burn up. Replaced the voltage regulator recently and still burning fuses. Is this a bad alternator or a short some place?
Thanks in advance for your help.
Jon1977 F350 Ranger XLT Camper Special 460/C6
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,095
Likes: 5,756
From: S/W Missouri, Polk county
Short some place yes, I'd 1st suspect the turning signal switch wiring, like inside the steering column. Have you double check all the wiring bundles for damage, mice chew, touching hot exhaust/tail pipe when moving down the road and being wind blown. Maybe a PO added in trailer plug back in the end harness?
Wiring schematics and other elec stuff start here. https://www.ford-trucks.com/forums/1...l#post14696846
Turning signal troubleshooting out of the Ford manual.
https://www.ford-trucks.com/forums/1...l#post18338355
Wiring schematics and other elec stuff start here. https://www.ford-trucks.com/forums/1...l#post14696846
Turning signal troubleshooting out of the Ford manual.
https://www.ford-trucks.com/forums/1...l#post18338355
Lead Driver
Joined: Jul 2017
Posts: 9,545
Likes: 1,156
From: San Jose, CA
Is this the main fusible link in the large black wire out at the starter relay? Or is it somewhere else?
A short in the turn signal shouldn’t blow the main fusible link or anywhere else for that matter if there’s a fuse in line 1st.
Speaking of fuses, have you blown any of the 30 ampers that you installed?
Sounds like it but I wanted to make sure.
As a 77 it should have a fuse for the turn signal in the main fuse box, I thought.
Something is strange here.
A short in the turn signal shouldn’t blow the main fusible link or anywhere else for that matter if there’s a fuse in line 1st.
Speaking of fuses, have you blown any of the 30 ampers that you installed?
Sounds like it but I wanted to make sure.
As a 77 it should have a fuse for the turn signal in the main fuse box, I thought.
Something is strange here.
Cargo Master
Joined: Jul 2005
Posts: 2,309
Likes: 364
From: Kansas
assuming nobody has shunted any fuses in the fuse box, your problem is most likely somewhere between the fusible link and the fuse box or any of the circuits that are not fuse protected...including the alternator and associated wiring. Most of the circuits, including the turn signals are protected by a fuse which should blow before the fusible link...hence the need to check for shunted/bypassed fuses. you could disconnect the alternator and test.
Lead Driver
Joined: Jul 2017
Posts: 9,545
Likes: 1,156
From: San Jose, CA
I forgot to ask if you have checked the voltage yet. Especially with the engine running.
The link blowing at higher speeds might lead to a bad regulator or alternator over charging the system. In my experience, usually that’s not enough to blow the fusible link, but perhaps you’ve got something else going on.
For example, have you installed a larger than stock, alternator at any point in the past?
Anybody that owns an older vehicle should ow at least one cheap voltmeter to test voltage in the system.
That can tell you a lot of things.
The link blowing at higher speeds might lead to a bad regulator or alternator over charging the system. In my experience, usually that’s not enough to blow the fusible link, but perhaps you’ve got something else going on.
For example, have you installed a larger than stock, alternator at any point in the past?
Anybody that owns an older vehicle should ow at least one cheap voltmeter to test voltage in the system.
That can tell you a lot of things.
Thread Starter
|
Trailering
Joined: Dec 2022
Posts: 15
Likes: 1
Short some place yes, I'd 1st suspect the turning signal switch wiring, like inside the steering column. Have you double check all the wiring bundles for damage, mice chew, touching hot exhaust/tail pipe when moving down the road and being wind blown. Maybe a PO added in trailer plug back in the end harness?
Wiring schematics and other elec stuff start here. https://www.ford-trucks.com/forums/1...l#post14696846
Turning signal troubleshooting out of the Ford manual.
https://www.ford-trucks.com/forums/1...l#post18338355
Wiring schematics and other elec stuff start here. https://www.ford-trucks.com/forums/1...l#post14696846
Turning signal troubleshooting out of the Ford manual.
https://www.ford-trucks.com/forums/1...l#post18338355
Thanks for the links on schemeatics and insight. Ill dig in and see what I can find
Thread Starter
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Trailering
Joined: Dec 2022
Posts: 15
Likes: 1
I forgot to ask if you have checked the voltage yet. Especially with the engine running.
The link blowing at higher speeds might lead to a bad regulator or alternator over charging the system. In my experience, usually that’s not enough to blow the fusible link, but perhaps you’ve got something else going on.
For example, have you installed a larger than stock, alternator at any point in the past?
Anybody that owns an older vehicle should ow at least one cheap voltmeter to test voltage in the system.
That can tell you a lot of things.
The link blowing at higher speeds might lead to a bad regulator or alternator over charging the system. In my experience, usually that’s not enough to blow the fusible link, but perhaps you’ve got something else going on.
For example, have you installed a larger than stock, alternator at any point in the past?
Anybody that owns an older vehicle should ow at least one cheap voltmeter to test voltage in the system.
That can tell you a lot of things.
So, a few responses:
1) yes im talking about the main link off the starter relay2) yes, have blown a number of 30 amp fuses3) ive replaced what I believe was the original voltage regulator with a spec electronic version4) i have not changed the alternator, though Im the third owner, so Ill see about getting a number off the existing and checking spec as well as metering the voltage and amperage at various RPMs
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Trailering
Joined: Dec 2022
Posts: 15
Likes: 1
assuming nobody has shunted any fuses in the fuse box, your problem is most likely somewhere between the fusible link and the fuse box or any of the circuits that are not fuse protected...including the alternator and associated wiring. Most of the circuits, including the turn signals are protected by a fuse which should blow before the fusible link...hence the need to check for shunted/bypassed fuses. you could disconnect the alternator and test.
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Lead Driver
Joined: Jul 2017
Posts: 9,545
Likes: 1,156
From: San Jose, CA
It’s good to check the voltage because if the regulator or alternator are failing and causing an overcharge situation, there’s always a possibility that it’s overheating the fusible links and fuses.
It’s a longshot maybe, because most of the alternators available for our trucks were in the under 70 amp range, and so not likely to burn out a link.
Even if overcharging.
And you want to know that it’s not overcharging so that you don’t ruin a perfectly good battery.
really need to work your way around all of the wiring to see if there’s anything obviously visible externally in the way of a crimp, crunch, bare wire, failing, splice, or similar, before you have to dig in deeper.
It’s a longshot maybe, because most of the alternators available for our trucks were in the under 70 amp range, and so not likely to burn out a link.
Even if overcharging.
And you want to know that it’s not overcharging so that you don’t ruin a perfectly good battery.
really need to work your way around all of the wiring to see if there’s anything obviously visible externally in the way of a crimp, crunch, bare wire, failing, splice, or similar, before you have to dig in deeper.
Thread Starter
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Trailering
Joined: Dec 2022
Posts: 15
Likes: 1
So a bit of checking and im certain i can use a new complete harness set for alternator, starter solenoid and voltage regulator. Preferably with factory plugs.
Any links to a source? All i see online are pieces of the whole set.
Many thanks!
Any links to a source? All i see online are pieces of the whole set.
Many thanks!
Lead Driver
Joined: Nov 2006
Posts: 5,217
Likes: 506
From: Pa.
Lead Driver
Joined: Jul 2017
Posts: 9,545
Likes: 1,156
From: San Jose, CA
What makes you think it’s that bad that it needs replacing?
It’s actually relatively simple to do yourself. If you’re good at splicing, but most people either are not good at it or just don’t want to tackle it.
However, if your truck has the gauges, then there probably isn’t a reproduction that doesn’t involve cutting and splicing anyway, because the shunt wires for the ammeter in the dash are part of the alternator control and charge harness.
And honestly, factory, looking or not, some modern connectors are way better than the originals. Although Ford did connectors very well, they didn’t always make them easy to service.
It’s actually relatively simple to do yourself. If you’re good at splicing, but most people either are not good at it or just don’t want to tackle it.
However, if your truck has the gauges, then there probably isn’t a reproduction that doesn’t involve cutting and splicing anyway, because the shunt wires for the ammeter in the dash are part of the alternator control and charge harness.
And honestly, factory, looking or not, some modern connectors are way better than the originals. Although Ford did connectors very well, they didn’t always make them easy to service.
Moderator & parts slinger
Joined: Feb 2007
Posts: 50,095
Likes: 5,756
From: S/W Missouri, Polk county
In case you want to replace the alternator wiring harness, that's the one that goes from the alternator to the regulator.
Harness, alternator wiring
Fits 78 f100-350 w/ amp and oil press. gauges all engines and 70 amp Ford alternator
D8TZ-14305-B
Green Sales, Cincinnati, OH (800) 543-4959
Just ran that part #. Green Sales is 0 in stock.
Harness, alternator wiring
Fits 78 f100-350 w/ amp and oil press. gauges all engines and 70 amp Ford alternator
D8TZ-14305-B
Green Sales, Cincinnati, OH (800) 543-4959
Just ran that part #. Green Sales is 0 in stock.
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