Subaru Forester Headlights Burning Out? (11 Common Causes)
The Subaru Forester is known for its off-road ruggedness, excellent safety ratings, and great visibility.
Like any other vehicle, you’ll need to replace its headlights every couple of years.
However, if your Subaru Forester’s headlights are regularly blowing out, this article can help you figure out the cause.
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Why Do My Subaru Forester Headlights Keep Burning Out?
A faulty headlight connector is one of the more common reasons for premature bulb failures, especially in older generations of the Forester. Other common causes include wiring and electrical issues, water intrusion, improper installation and using aftermarket bulbs.
1. Headlight Connector Issues
Headlight connectors in the first and second-generation Forester have a tendency to develop cracks or melt over time.
It happens more quickly if you use higher output bulbs that produce more heat, but they can also melt even with the stock bulbs.
Here’s how a few owners on the SubaruForestor.org forum described the problem:
“On my ’99 Forester they melted and got brittle.”
“On my ’02 one comes out loose and the other comes out with some coercion.”
“Those headlight connectors are known to overheat, get hot and crack etc. I believe others have posted that heavy duty ones are available at chain parts stores.”
“Subaru headlight connectors do melt over time, even with stock wattage bulbs.”
Newer Foresters starting with the third generation model use a different type of headlight connector that can come loose if the plastic tab that locks it in place wears out or breaks.
Headlight bulbs will have shorter lifespans if they’re:
- Constantly turned on and off
- Not getting the right voltage
- Operating at higher temperatures
If the headlight’s electrical contacts aren’t making a good connection, it might cause sparks that can abnormally heat up the bulb and melt the connector.
A weak connection can also cause the lights to rapidly turn on and off. This increases the possibility of electrical surges which can blow up the bulb. It also causes the bulb to rapidly heat up and cool down, which weakens the glass and the filament, and shortens its overall lifespan.
A brittle, cracked or melted connector should be replaced immediately. Bulb connectors are fairly cheap and can be easily spliced in after cutting off the old ones.
Many aftermarket headlight connectors are even more durable than the stock units, especially the ones made out of ceramic.
If it’s just the plastic locking tabs that are broken, you can insert a small piece of rubber or foam on the sides to make it fit snugly again.
2. Corrosion Problems
Corroded wires and electrical contacts don’t conduct electricity very well and might cause your headlight to become dim or intermittently flicker, along with other electrical gremlins that can shorten the life of your headlight bulbs.
Corrosion also increases the resistance in the circuit and increases the amount of heat it generates, which can make your bulbs burn up quicker.
Here’s how two Subaru owners described their experience:
“We had this issue on our Subaru and after 3 sets of bulbs I happened to clean the battery terminals from all the corrosion and tightened a loose ground and it stopped happening.”
“The issue was the large gang plug immediately below the hi beam lamp. The female portion was not fitting well and there was corrosion on the contacts. Cleaned up the contacts with contact cleaner, a little dielectric grease, and plugged it back together and Presto! problem fixed!”
To make sure the headlight wiring is working properly, check the following for signs of rust or white debris:
- Inside the headlight connector
- Battery terminals
- Ground wires
- Inside the fuse box
After inspecting the wiring and electrical contacts, scrape off any signs of corrosion with a toothbrush, some sandpaper, or even with just the tip of a screwdriver.
Many people also apply dielectric grease inside the bulb connector to prevent corrosion.
3. Improper Handling of the Bulb
Touching halogen bulbs with your bare hands smears oils, salts from your sweat, and other contaminants onto the bulb which significantly lowers its lifespan.
Halogen bulbs operate at really high temperatures and the oils can cause the bulb to heat up even more which will eventually cause the glass to crack or even explode in a short amount of time.
To avoid contaminating the glass, wear clean gloves or at least use some clean paper towels whenever you handle the headlight bulb outside of its packaging.
The bulb and its filament are also very delicate, so handle it with care during the installation process.
If the bulb appears dirty or contaminated, clean it with rubbing alcohol and let it dry thoroughly before installing.
4. Aftermarket Bulbs
Non-standard aftermarket halogen bulbs have lower lifespan ratings which means you’ll be replacing them more often.
Bulbs that run at higher wattages do produce more light, but also generate more heat. This not only results in a shorter lifespan, but can also damage the connectors, wiring and headlight assembly.
Cheap replacement bulbs that run at the same wattage as the stock ones also don’t last as long because they use lower quality materials.
OEM headlight bulbs are usually rated for around 1,000 hours while aftermarket bulbs might only be rated for a few hundred hours.
If you’re already using OEM bulbs, but they still keep burning out in just a few months, you might want to grab a set from your nearest Subaru dealer to make sure you’re getting the original part.
5. Water and Condensation Issues
Too much moisture getting into the headlight assembly can cause short circuits that quickly destroy the bulbs.
If the water makes contact with the hot bulb, it can cause a sudden change in temperature and weaken or shatter the glass. The extra humidity can also make the electrical contacts corrode or rust prematurely.
Below are some of the ways water can get into the headlight:
- Condensation due to excess humidity and/or rapid temperature changes
- Cracks in the lens
- Damaged headlight seals
The headlights in the first and second generation Subaru Foresters have a cover in the back that protects the bulbs and electrical contacts from water damage.
If this gets broken or isn’t installed properly, the bulbs are more likely to get damaged by splashes of water and heavy rain. You’ll also see more condensation than normal.
If there is only a small amount of condensation in the headlight assembly, it will likely evaporate within a few days or if you keep the headlights on for an extended period. However, be sure to keep the engine running while doing so to avoid draining the battery.
You can also blow dry the lens to speed up the evaporation. You can even take out the bulbs and blow dry the inside of the headlight through the opening.
If you see droplets or pools of water inside the headlight and you’re constantly replacing the bulbs, you might need to replace the assembly completely. You can take it back to the dealer for a replacement if the car is still under warranty.
If you suspect that the water leaks are caused by broken seals, you can apply a layer of silicone around the edges of the lens to seal it back up. Cracks in the lens can also be repaired in the same manner.
You can also pry off the lens completely by applying heat around the edges until the adhesive breaks down completely. Once it’s off, you can reattach it using some type of glass sealant or silicone.
6. Automatic Headlights
Using the automatic headlight feature usually results in more frequent bulb changes since they’re running for longer periods of time.
Automatic headlights became available in the fourth gen Forester which was introduced in 2014.
Adjusting the sensitivity of the automatic headlights in the vehicle’s settings or simply switching them on manually can help prolong the longevity of the bulbs.
The fifth gen Forester switched to LED headlights which last at least 10x to 20x longer than halogen bulbs, so using the auto headlight feature shouldn’t be much of a concern.
However, you might want to avoid using it if you’re concerned about longevity since the LED headlights are not serviceable and cost at least $1,000 per side to replace.
7. Excessive Vibration
The filament inside the bulbs are rather delicate and can easily break if they’re constantly subjected to harsh vibrations.
Excessive vibrations are usually caused by:
- Off-road driving
- Potholes and rough roads
- Headlight assembly not bolted down tightly
- Headlight bulbs not locked in place
- Worn out engine mounts or suspension
If the bulb is not properly installed, it will just be rattled to death in the headlight fixture. The headlight bulbs in the first and second generation Forester are held in place by a metal retaining clip. In newer Foresters, the bulb has to be turned clockwise to lock it in place.
You should also check if the headlight assembly has any movement at all. You might need to tighten it down or replace any worn out or missing brackets.
Excessive vibration can also be caused by worn engine mounts and suspension components. While some owners may not find it too bothersome, particularly in older vehicles, the constant shaking will significantly shorten the lifespan of the bulb.
8. 12-Volt Battery Issues
If the 12-volt battery has trouble holding a charge, it’s not going to be able to provide the correct voltage to the headlights which will lower the bulb’s lifespan.
Halogen bulbs don’t work very well at lower voltages because they can’t reach the right operating temperatures and the tungsten ends up accumulating on the glass bulb instead of getting deposited back onto the filament.
Aside from turning the bulb brown and making the light look extremely dim, the filament gets used up pretty quickly.
According to Osram, a five percent deviation in the operating voltage can affect lamp life by up to 50 percent.
Most car batteries last around 3 to 4 years. If you haven’t had a new battery fitted in a couple of years and you’re frequently replacing the bulbs, it might be time for a replacement.
You can also test the battery with a multimeter or take it to AutoZone where they can do a proper load test.
How to Test the Battery
- Turn the headlights on for 2 minutes to remove the surface charge
- Set your multimeter dial to the ’20 Volts’ setting.
- Turn off the car
- Connect the red probe to the positive battery terminal; black probe goes to the negative
If you see less than 12 volts on the meter, you might need to replace it as it can no longer hold a charge.
Corrosion on the battery terminals can also prevent the battery from providing enough power to the car’s electrical system.
If you see any white deposits on the battery, disconnect the battery terminals and clean them out using a toothbrush dipped in a baking soda and water mixture. Make sure the bolts are tight when you reconnect the terminals.
9. Alternator Problems
A faulty alternator or voltage regulator will have issues sending the right amount of voltage to the electrical system and cause your headlights to burn up quickly.
When the engine is running, the alternator should produce between 13.5 to 14.9 volts. If it goes past 15 volts, your headlights are going to quickly die and you’re likely to experience different electrical issues.
You can test the alternator’s voltage output using a multimeter. The process is similar to the steps outlined previously for a 12-volt battery test. You just need to turn on the engine to get a proper reading.
You can also plug a voltmeter into the 12-volt accessory outlet, also known as the cigarette lighter socket, if you want to constantly monitor your voltages while driving.
For these types of issues, it’s best to take your car to a mechanic or an auto electrician for a proper diagnosis. Many parts stores can also test if your alternator is working properly if you’re trying to minimize costs.
10. Wiring Problems
Broken, melted or frayed wiring can cause short circuits and all sorts of strange electrical issues that can destroy your headlights pretty quickly.
One of the more common wiring issues you want to look out for is broken or worn out bits of insulation. When the wires are exposed, they can easily cause short circuits.
Wiring insulation can be compromised by:
- Deterioration over time
- Getting caught or pinched on body panels
- Chewed up by rodents
You should also check for frayed wiring at the different connection points. The copper wires inside the insulation can also break over time and weaken the integrity of the circuit.
Broken strands of wire will increase the resistance of the wiring which results in more heat. The weaker electrical connections can also intermittently make your lights turn on and off, as well as create voltage issues, which shortens the lifespan of the headlights.
Identifying wiring issues can be difficult without the help of a mechanic or an auto electrician. However, you can visually inspect the wiring for visible breaks, fraying, or missing insulation, as well as evidence of burn marks or melting, which are indicative of wiring problems.
You can also turn on the headlights and check if any of the wires become excessively hot.
Fortunately, replacing the headlight warning harness is usually fairly simple and affordable.
You should also check the ground wires connected to the chassis for potential damage, corrosion or loose connections, as these can cause a range of electrical problems.
11. Faulty Body Integrated Unit
Headlight issues can be also caused by a faulty BIU or Body Integrated Unit.
The BIU is what Subaru calls its Body Control Module. It’s responsible for controlling the car’s entire electrical system.
It can be easily damaged by short circuits or overloading caused by aftermarket electronics like lighting or sound system upgrades.
The chips and solder joints inside the BIU can also wear out over time and cause all sorts of strange or intermittent electrical issues such as flickering headlights and blown fuses.
If you’ve already crossed out all the other possible causes in this list and you still can’t figure out why your headlights keep burning out, have a mechanic check the BIU for possible issues.
You might also solve your BIU problems by removing any aftermarket electrical or wiring modifications that have been done to the vehicle.