Your car key fob might seem tough, but inside it’s a delicate piece of technology. One of the most common causes of failure is water damage—and unlike your mobile phone, it usually doesn’t recover after being left in a puddle, washed with clothes, or dropped in the sink.
In this post, we’ll explain what actually happens when water gets inside your car key fob, the signs of damage, and what to do if it happens to you.
Why Water and Car Keys Don’t Mix
Modern car keys are more than just bits of plastic—they’re mini computers with:
- A printed circuit board (PCB)
- Microchips and resistors
- A transponder chip for the immobiliser
- Buttons, rubber contacts, and soldered joints
When water seeps inside the casing, it causes short circuits, corrosion, and mineral deposits that interfere with these electronic components. Even if the key still works at first, damage can build up over time.
What Happens When Water Gets Inside
Here’s what really happens once your fob is exposed to moisture:
- Instant Short Circuit – Water bridges connections on the circuit board, causing electrical failure.
- Corrosion – Over days or weeks, tiny amounts of water create rust and green residue (oxidation), which slowly eats away at the metal.
- Battery Damage – The coin cell battery can leak, swell, or stop working entirely.
- Transponder Failure – If the transponder chip is affected, your car won’t start—even if the mechanical key still turns in the ignition.
Common Signs of Water-Damaged Car Keys
- Buttons work intermittently (sometimes unlock, sometimes don’t).
- Remote unlock/lock completely stops working.
- Car won’t recognise the key (immobiliser light stays on).
- Visible condensation or fog inside the fob casing.
- Corrosion on the battery contacts.
Can a Wet Car Key Be Fixed?
- Immediate Action: If your fob gets wet, remove the battery immediately and dry everything thoroughly. Do not press the buttons.
- Professional Cleaning: In some cases, a locksmith may clean and repair the PCB with specialist tools.
- Replacement: If the transponder chip is damaged, the only solution is a replacement key.
Tip: Unlike remotes, transponder chips do not need a battery to start your car—but once water damages the chip itself, it’s game over.
How to Prevent Water Damage
- Keep keys in a protective silicone case to reduce exposure.
- Avoid leaving keys in pockets when swimming, exercising, or working outdoors.
- Keep spare keys safe and dry at home.
- If your key is exposed to rain, dry it quickly and check the battery contacts.
What to Do If Your Key Fob Fails
At 247 Auto Locksmith, we provide:
- Replacement key fobs (genuine, OEM, and aftermarket options).
- Professional key programming on-site.
- 24/7 mobile service across Surrey, West Sussex, South London, and Kent.
If your key has suffered water damage and stopped working, call us today for fast, professional help.
Call or WhatsApp: 07921 365 247
FAQs
Can I put my car key in rice to dry it out?
Rice may help with surface moisture, but it won’t stop long-term corrosion. Professional cleaning or replacement is the only reliable solution.
Why does my key work sometimes after water exposure?
That’s intermittent corrosion—metal contacts are partially damaged, so performance becomes unreliable until it fails.
Does insurance cover water-damaged keys?
In some cases, yes. Check your vehicle or home insurance policy.
Conclusion
Water damage is one of the most common—and preventable—causes of key fob failure. Acting quickly can sometimes save your key, but often a replacement is the most reliable option.
At 247 Auto Locksmith, we stock and program 90% of keys on the spot. If you’ve had water damage to your car key, don’t wait for it to fail—call us today and we’ll get you back on the road.