You probably already know that all electrical parts need fuses for safety and to make sure they don’t break. The generator is no different. Even though the generator fuse is big and strong, it can still blow when it’s under a lot of stress. If it breaks, the generator will no longer be able to charge the battery. It’s pretty much the same as having a bad battery when this happens.
If the generator fuse blows, the lights will be dim, the engine will lose power, the engine will stop running, and a battery warning light will come on. Also, the battery will die soon after these symptoms show up, and based on the car, you may also notice other electronic or electric problems.
A Difference Between an Alternator Fuse and a Fusible Link
A common alternator fuse is in almost all new cars and a lot of older ones as well. The fuse is much bigger than the others because it can handle up to 100 amps. The fuse box for this fuse is either in the cabin or, more often, in the engine. It’s also in the same place as other fuses. An in-line fuse can also be used sometimes. The fuse is then in the middle of the cable from the generator to the battery.
The fuse is still the same, but the alternator wire has a single terminal built into it. When it comes to alternator wires, alternator fusible links do the same thing as a fuse. Certain materials and exact thicknesses are used to make one part of the wire so that it breaks at the same time as a normal fuse with the same amp rating.
Because they are right between the battery and the generator, fusible links are a little safer than regular fuses. That means that if there are voltage spikes, they are less likely to break the fuse before they go through it. A fusible link also saves room in the fuse box, which is important when you think about how big a 100-amp fuse is and how thick the alternator wires are. In the end, though, a fuse and a fusible link do the same thing.
Signs of a Blown Alternator Fuse or Fusible Link
1. Turn Down The Lights
If the generator fuse blows, one of the first things you’ll notice is that the lights will be dim. This happens because the alternator isn’t doing anything, so the battery slowly dies while you drive. The engine and all of its electric parts are then running on the battery alone, which isn’t designed to handle such heavy loads.
As you drive at normal speeds, the battery slowly dies, and the first thing you’ll notice is that the headlights and internal lights are dimming. As you drive, the lights will get dimmer and dimmer until the engine stops. It is important to note that headlights and internal lights that are too dim can be caused by other problems with the charging system.
These could be, among other things, a bad generator, a bad voltage regulator, or a bad battery. But those parts rarely make the lights get dimmer and dimmer before they shut down the engine. Instead, they will keep the headlights on, but a little less bright than normal. That is, unless the alternator is totally broken and not charging the battery at all, which doesn’t happen very often.
2. Engine Power Drops
Another important sign is a lack of engine power, which in some cars may be the first one to show. The engine power will slowly go away until it’s not even enough to move the car in first gear, just like when the headlights get dim. If the alternator fuse blows, the spark plugs have to run off the battery, which is bad because spark plugs need a lot of power.
The spark will get weaker and weaker at high RPMs, then weaker and weaker at mid-RPMs, and so on, as they slowly drain the battery. At the same time, the fuel pump uses a lot of electricity, and as the battery dies, it stops working as well. When you’re going slowly, you won’t notice because the engine is only using 10–15% of the fuel pump’s output.
But as you drive or really push the car, you’ll notice that the engine starts to run out of gas and almost stops. If this starts to happen, drive as slowly as you can until you get home or to the first car parts or repair shop. The reason for this is that the air-fuel blend is becoming less dense, which can melt and damage the engine’s internals.
3. The Engine Stops
When the battery is dead, the engine often stops running. The engine will sometimes stall in that case, but it will work fine when it’s going. It works the same way when the generator or voltage regulator is broken. But if the generator fuse blows, the engine will slowly shut down and show the same signs of low power and dim lights. After that, you won’t be able to start the engine again.
And there’s a chance that you get where you’re going without any problems because you drive carefully. Then, when you try to start the engine again, either the battery is dead or the engine stops running soon after starting. This is because the battery was already very low from the last run.
It had enough power to keep the engine going, but not enough to turn it over or turn it fast enough to start. This kind of sign also shows up when the alternator breaks, but not very often in other situations.
4. Light For Battery Warning
Almost all cars, no matter how old they are, have a battery warning light. The light turns on when the voltage of the battery goes below a certain level. And that happens pretty quickly when the engine is running with the alternator fuse blown. A medium-sized battery lasts for about 3 to 5 miles, or 10 minutes, of driving on a small engine. Before the engine stops.
The battery warning light will then come on a lot faster, if not right away. Of course, if there are any problems with the charging system or battery, the charge warning light will come on. That includes a bad alternator, an old battery, a bad voltage regulator, broken wires, too many aftermarket accessories, power draws from other devices, and a lot of other things.
If the only sign is a battery danger light, you should get the battery and alternator checked out first. You can use a multimeter to do that yourself or get it done for free at any AutoZone or NAPA shop. However, it is much easier to check the generator fuse, so there is no reason to skip that step.
5. Battery That is Dead
An alternator breaker that blows will leave the battery dead. All of the above signs are caused by a battery that is constantly losing power, and it will only be a matter of time before it dies completely. The engine usually stops just before that, and if you try to start it again after that, the battery will die. If you drain the battery, even if it’s brand new, it can get damaged and won’t last as long.
Also, the cleaning mode doesn’t always work, so you might not be able to charge it at all. In any case, if you see any of the above signs, don’t try to start the engine after it has stalled. The engine won’t start, and you’ll hurt the battery in the process. Another thing is that a drained battery can be caused by other problems, so this sign by itself is not proof.
6. Different Problems with Electricity or Electronics
When the alternator fuse breaks, a lot of different electrical problems happen in modern cars. For modern cars to work, they need a steady 12-volt power source. In other words, if there is a voltage drop, different sensors can start to fail, which makes the engine misfire and run rough.
Also, the electric hand brakes, power windows, power seats, power locks, and any other electric parts will either stop working or only work sometimes. These days’ cars also have entertainment systems, computers, and electronic gauge clusters. All of those things also need a steady power source; if they don’t have one, they will start glitching, shutting down, and acting strangely.
How Does a Damaged Alternator Fuse Fail? How to Wire
Damaged Wiring
Almost any kind of short circuit can damage the alternator fuse, but wire damage is the most common one. It’s easy to get the wires to go in the wrong direction on older cars that get a lot of maintenance and big repairs. What’s going to occur in the engine compartment? The wires are likely to touch something hot, which will melt them and short them out.
The same thing will happen if you lean the wires against something sharp, because the engine is always vibrating. If the battery fuse fails again soon after you replace it, you should look into this more. Around the exhaust manifold and the intake manifold is where wires get broken the most often. Check the wires around the exhaust right after the exhaust pipe as well. In fact, though, the short could be anywhere.
Alternator In Trouble
Another pretty common reason for a generator fuse to blow is a broken alternator. There are many ways for an alternator to break, and the bolts that hold it together can even come loose. When the alternator breaks, it can cause a short between the rotor and the stator. This will cause the alternator fuse to blow very quickly. This can also happen with a bad voltage control or a bad diode bridge.
There are Too Many Aftermarket Auxiliaries.
It’s easy for aftermarket accessories to draw too much power, which the alternator and its fuse can’t handle. Like amps, extra speakers, bar lights, winches, and anything else that uses electricity. It’s important to note that almost all cars can handle an extra speaker, subwoofer, or light bar.
Those parts can only blow the fuse if they are a lot stronger than what the car already has. Also, it’s very easy to short these aftermarket accessories while they’re being installed, especially if the job is done by someone who isn’t skilled. Then you should pay the most attention to these, especially if you put them in right before the fuse blew.
Using Jumper Cables to Short Out the Battery
If you do it wrong, jump-starting a dead car battery can do a lot of damage. It seems pretty clear that the positive terminal on the source car should connect to the dead battery’s positive terminal. The negative terminal should connect to the dead battery’s negative terminal. But even though you know it can happen. You still mix up the positive and negative connections because they aren’t always clearly marked.
It’s also possible that two people did it. With one connecting the red jumper wire to the negative terminal and the other to the positive terminal. No matter what, if the battery terminals are not matched, it can damage the alternator fuse, especially on the source car. You should know that this kind of behavior can cost thousands of dollars in damage, so think of yourself as lucky that only the fuse blew.
Price to Change the Fusible Link and Fuse
It’s not too expensive to replace a common alternator fuse, no matter where it is located. It’s as easy to change a 100-amp fuse as it is any other fuse, and it costs less than a dollar. Find out where it is, which can be done quickly by reading your owner’s guidebook or looking under the fuse box cover. “ALT” is commonly written on the alternator fuse. There should be one in each of the two fuse boxes. If not, check the wire that goes from the alternator to the battery.
Costs for alternator fusible links vary from $15 to $30, based on the type, grade, and car. Sometimes all it takes to replace them is taking off two bolts and putting in a new one. Other times, soldering and skilled insulation are needed. If cutting wires is something you need to do, it’s best to let a professional do it unless you have experience. That job should cost about $50 to do.
conclusion
If you have a blown alternator fuse or a fusible link, you will slowly start to notice very bad signs. Still, you won’t have gone more than a few miles between the first signs and the engine stopping for good, so you won’t have much time to think about them.
It’s very easy to check the fuse and fusible link, so if you think that’s the case, don’t wait any longer—get out your owner’s guidebook and look for the fuse.
