* Overload: The alternator is being forced to work harder than it's designed for. This could be due to:
* Excessive electrical load: Too many accessories running (headlights, heater fan, radio, etc.) simultaneously. A faulty accessory drawing excessive current (e.g., a short circuit in a power window motor). A parasitic drain (current draw even with the vehicle off) draining the battery, forcing the alternator to constantly recharge.
* Faulty voltage regulator: The voltage regulator controls the alternator's output. If it's malfunctioning, it may allow the alternator to overcharge, producing excessive heat. This is a very common cause of alternator overheating.
* Weak or failing battery: A weak battery forces the alternator to work harder to maintain voltage, leading to overheating.
* Internal Problems within the Alternator:
* Worn bearings: Worn bearings increase friction and generate heat.
* Stator or rotor problems: Internal shorts or damage to the stator windings or rotor can cause significant heat buildup. This often leads to a burning smell.
* Poor internal connections: Loose or corroded connections inside the alternator increase resistance and generate heat.
* Diode failure: Diodes rectify AC current to DC. A faulty diode will cause excessive current flow and heat.
* External Factors:
* Poor belt tension: A loose belt slips, causing the alternator pulley to spin inefficiently and generate heat. Conversely, *too* tight a belt can also cause excessive bearing wear and heat.
* Restricted airflow: Lack of proper ventilation around the alternator can prevent heat dissipation. Dust, debris, or a blocked airflow path can contribute to this.
Troubleshooting Steps:
1. Check the obvious: Listen for unusual noises (whining, grinding) coming from the alternator. Smell for burning insulation. Check the belt tension – it should deflect slightly when pressed.
2. Test the battery: Have the battery and charging system tested at an auto parts store. They can assess the battery's condition and measure the alternator's output voltage.
3. Inspect the voltage regulator: This is often part of the alternator but can be a separate component. Check for any signs of damage or overheating. A faulty regulator is a highly likely culprit.
4. Check for parasitic draws: Disconnect the negative battery terminal and measure the current draw using a multimeter. Any significant current draw (more than a few milliamps) indicates a problem elsewhere in the electrical system.
5. Visual inspection of the alternator: Check for loose connections, signs of overheating (discoloration), or physical damage.
If you're not comfortable working on car electrical systems, it's best to take your Blazer to a qualified mechanic for diagnosis and repair. Ignoring an overheating alternator can lead to more serious damage, including a complete alternator failure.
