the heating and deformation of the car fuse box is also a very serious safety hazard and must be dealt with immediately. the principle is similar to the household fuse box, but the cause and scene are more characteristic of the car electrical system.
core reason: abnormal high current or high resistance leads to overheating
the role of the car fuse is "circuit guardian". when the current exceeds its rated value, it will melt to protect the lines and equipment behind it. if it itself or the surrounding area heats up and deforms, it means that it has become a "hot spot".
main reasons for analysis:
1.excessive contact resistance (most common cause)
2.poor contact between the fuse and the socket: if the metal contacts in the fuse box become loose, oxidized, corroded, or lose elasticity due to repeated insertion and removal, contact resistance will occur. when current flows through this point, a significant amount of heat will be generated.
3.loose plug or harness connector: if the harness plug connected to the fuse box is not properly inserted, or if the pins are oxidized or bent, it can increase contact resistance and cause localized overheating.
4.overload or short circuit of electrical appliances
5.internal fault of connected appliance: when components like headlights, fans, or seat heaters connected to the fuse experience internal short circuits or malfunctions, the operating current remains near the fuse's rated current without reaching it. although the fuse stays intact, prolonged high-load operation causes overheating.
6.line short circuit: in the line after the fuse, the insulation is worn and broken, and the body metal is in contact with the body metal, forming a local short circuit, resulting in increased current.
7.using mismatched or low-quality fuses
8.excessive current: if a fuse with a higher rated current (e.g., 25a instead of 15a) is installed, the circuit may exceed its rated capacity during abnormal conditions. however, the fuse might not blow promptly, causing overheating of both the circuit and the fuse box.
9.poor-quality fuse: fake and inferior fuse may use inferior materials, its internal resistance is high, easy to heat, and the fusible characteristics are not accurate, unable to provide effective protection.
10.installing high-power appliances without authorization
11.if high-power equipment such as speakers, spotlights, and car inverters is installed later, and power is drawn directly from an existing fuse, the circuit may be overloaded for a long time, exceeding the original vehicle's design load capacity.
12.the fuse box itself is aging or has internal faults
13.the metal conductor (mother bar) inside the fuse box is corroded or broken due to long-term use, vibration or moisture, resulting in increased resistance.
14.internal circuit board (if it is an active fuse box or smart distribution module) is faulty.
potential dangerous
1.vehicle fire: this is the most terrible consequence, high temperature may ignite the plastic of the fuse box and the surrounding wire harness.
2.function failure: continuous high temperature will melt plastic, resulting in deformation of fuse holder, unable to fix the fuse, resulting in circuit break, related function failure (such as car lights not working, air conditioning does not work, etc.).
3.line damage: heat will be transmitted along the wire backward, damaging the electrical appliance or melting the insulation layer of the wire, resulting in a larger short circuit.
4.difficult to repair: once the fusible link box body melts and deforms, it often needs to replace the entire fusible link box assembly, and the repair cost is high.
what you should do right now
warning: if you smell burnt plastic or see smoke, stop safely and turn off the engine immediately. stay away from the vehicle!
1. stop and turn off the engine immediately:
· park the vehicle in a safe area as soon as possible under the premise of ensuring safety.
· turn off the engine and disconnect the negative battery terminal. this is the most critical safety step to cut off the vehicle's power supply and prevent the fault from spreading or the risk of electric shock.
2. preliminary identification and cooling:
· after disconnecting the battery, try to feel (careful of burns) or observe with your hands to find which fuse or area is abnormally hot.
· never touch or attempt to remove fuses without disconnecting the power supply.
3. call for help:
· do not attempt to continue driving! this is extremely dangerous.
· contact your car insurance company (which usually offers free roadside assistance), 4s store, or professional repair shop to request towing service and send your vehicle to the repair shop for inspection.
professional maintenance process
after the vehicle is sent to the repair shop, the professional technician will do the following:
1. visual inspection: carefully inspect the deformed fuse box, burned-out fuses, and related wire harness connectors.
2. circuit check:
· use a multimeter to measure the fault circuit current and determine whether there is an overload.
· measure the resistance in the circuit to check for short circuits or high resistance points.
3. load check: check all the electrical appliances corresponding to the fuse, and check one by one which electrical appliance is faulty to cause overload.
4. line inspection: check the whole section of the wire bundle from the fuse box to the electrical appliance to see whether there is wear, skin break and grounding.
5. repair and replacement:
· replace all damaged parts: including blown fuses, burned-out sockets (if replaceable individually), or the entire fuse box assembly.
· repair the root cause: repair or replace the faulty electrical appliance, repair the damaged wiring harness.
· ensure all connections are tight and free of oxidation.
summary and prevention
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