What to Do With a Water Damaged Car Key
A water damaged car key is taken out of the water, wiped until it is completely dry, kept away from heat and left unpressed, and the spare key is used until the wet key has been checked.
Inta-Lock Car Key Guides. Updated October 2026.
Water harms the electronic parts of a car key and leaves the mechanical part alone. The key fob battery and the circuit board are the parts at risk, the transponder chip holds no battery of its own, and the blade is solid metal.
A key that works straight after it got wet is not proven sound, because the residue the water leaves on the circuit board corrodes it after the key has dried. This guide gives the first actions in order, what water does to each part of the key and the signs of damage.
What Do You Do First When a Car Key Gets Wet?
Five actions, in order, deal with a car key that has just got wet, and the first is to wipe the key until it is completely dry.
- Take the key out of the water and wipe it until it is completely dry. One manufacturer handbook gives that instruction for a key that gets wet, and it says immediately.
- Leave the buttons alone. A press draws current from the key fob battery across a wet circuit board.
- Keep the key away from heat. Manufacturer handbooks tell owners to protect a key from high temperatures, which rules out a radiator, a hairdryer and a tumble dryer for a wet fob.
- Open the handbook of the car at the page on the key fob battery. It shows whether and how the owner takes the cell out, and a key with the cell out carries no current across the wet board.
- Use the spare key for the next journey. The car stays in use while the wet key dries and is checked.
A driver with no spare key reaches the car through the blade, which on a keyless key is stored inside the fob.
What Do You Not Do With a Wet Car Key?
Four things are kept away from a wet car key, heat, button presses, fingers on the circuit board and unsourced drying methods.
- Heat. Heat is the hairdryer, the radiator, the oven and the tumble dryer. One manufacturer handbook tells owners not to leave its key for an extended period anywhere above 60 degrees Celsius.
- Button presses. Button presses are tests of the remote made while the key is still wet. Manufacturer handbooks tell owners to avoid unnecessary operation of a remote even when it is dry.
- The circuit board. The circuit board is the board inside the fob that carries the electronics. One manufacturer handbook tells the owner who changes a battery not to touch the circuit board or a battery terminal.
- Unsourced drying methods. Unsourced drying methods are rice, sprays and cleaning fluids. No manufacturer handbook read for this guide names rice, a cleaning fluid or a set drying time for a key, so this guide prints none.
A key fob battery that comes out of a wet key is a button battery. The Office for Product Safety and Standards, in its button battery safety campaign, tells households to store a removed cell securely and to recycle it promptly, because a dead button battery still holds enough power to badly hurt a small child.
A car key that has been in water in Leicester or Leicestershire? Call Matt with the make of the car and what still works, and a quote is agreed before work begins.
Call Matt on 0116 442 2084Does the Car Still Start When the Wet Key Fob Is Dead?
A car with a bladed transponder key still starts when the wet key fob is dead, because the car powers the chip, and a keyless car starts through the backup its maker provides.
The driver door comes first. One manufacturer handbook tells the owner of a car with a failed remote to unlock the driver door by inserting and turning the key blade in the lock cylinder.
For a keyless car, the handbook of the car shows where the key is held for the car to read it when the key fob battery is flat. An engine that stays stopped with the wet key and starts with the spare key places the fault in the chip of the wet key.
What Does Water Do to Each Part of a Car Key?
Five parts of a car key meet water in different ways, and only two of them, the key fob battery and the circuit board, are harmed by it directly.
| Part of the key | What water does to it | What still works | What it means for the driver |
|---|---|---|---|
| Key fob battery | Water bridges the two faces of the coin cell and drains it | Nothing on the remote side until a new cell of the type the handbook names is fitted | A drained cell is the mildest outcome |
| Circuit board and buttons | Water bridges the tracks while the cell is fitted, and the residue it leaves corrodes the tracks and the button switches after the key has dried | The blade and, on many keys, the transponder chip | This is the part that decides between a repair and a new key |
| Transponder chip | The chip holds no battery, so water finds no current in it. A chip built into the circuit board shares the fate of the board | A separate sealed chip still answers the immobiliser | A car that starts with a dead remote has a sound chip |
| Blade | Water does not harm the cut metal in the short term | The door lock and, on a bladed key, the ignition lock | The blade is the way into the car while the remote is dead |
| Case, seals and button pad | Water passes the joins and the button pad and stays trapped inside | The case still holds the parts | A key that looks dry outside is still wet inside |
A wet key with a dead remote often still opens the door and starts the engine, because the blade and the chip outlast the fob electronics.
Does a Car Key Still Work After Getting Wet?
A car key often still works after getting wet, because a short splash does not always reach the circuit board, and a key that works on the day is still not proven sound.
Damage from water has two stages. The first is the short circuit while the key is wet and the cell is fitted. The second is corrosion, which grows on the tracks and the battery contacts after the key has dried, so a key that passed its first test sometimes fails later.
What Are the Signs of a Water Damaged Car Key?
Five signs show that water has damaged a car key, and each points to the battery, the circuit board or the chip.
- Shorter range. Shorter range, a remote that works only close to the car, points to a drained key fob battery or to corroded battery contacts.
- Buttons that work now and then. Buttons that work now and then point to residue under the button switches of the fob.
- A new battery that runs flat. A new battery that runs flat soon after it is fitted points to corrosion on the circuit board of the key.
- Green or white deposit. Green or white deposit on the battery contacts is corrosion, and it marks a key that water has reached inside.
- An engine that does not start. An engine that does not start while the lights of the car stay bright points to the chip of the key or to the board that carries it.
The signs do not always appear on the day the key got wet. A key that shows one of them is sorted by symptom in the guide to a car key that is not working.
What Happens to a Car Key in the Washing Machine?
A car key in the washing machine is fully immersed, tumbled and soaked in detergent, so the water reaches the circuit board and leaves residue on it.
The key stays under water for the whole cycle, detergent stays inside the case as a film, and a warm wash or a tumble dryer adds the heat that manufacturer handbooks tell owners to keep away from a key.
The blade and a separate sealed transponder chip often come through a wash, so a washed key with a dead remote often still opens the door. The first actions are the same five as for any wet key.
Is Salt Water Worse Than Fresh Water for a Car Key?
Yes, salt water is worse than fresh water for a car key, because salt water conducts electricity well and the salt left behind keeps corroding the circuit board after the water has dried.
One manufacturer handbook names both in the same warning and tells owners not to let the key come into contact with water or salt water.
Clean rain leaves little behind. Sea water leaves salt, pool water leaves chlorine, a wash leaves detergent and a spilled drink leaves sugar, and each residue stays on the board of the fob.
Wiping a key that has been in the sea removes the water on the outside and leaves the salt inside the case.
Is a Water Damaged Car Key Repaired or Replaced?
A water damaged car key is repaired where the fault is limited to the key fob battery, the contacts or the case, and replaced where the circuit board or the chip has failed.
Three things decide it, what the water carried, how long the key stayed wet with its cell fitted, and the type of key. The cost follows the same three things. No price list is published, and a quote is agreed before work begins.
A replacement is a new key cut and programmed to the car. An auto locksmith is called when the dried key shows a sign of damage or when the wet key was the only key, and whether one wet key is repaired or replaced is confirmed on the call.
What Follows Once a Wet Car Key Has Dried?
Four questions sit next to a car key that has been in water.
How Does Drying a Wet Key Differ From a Key Fob Repair?
Drying a wet key removes the water, while a key fob repair deals with what the water left behind in the remote electronics.
Corroded contacts, dead button switches and a damaged case are faults of the remote electronics, and that work belongs to key fob repair in Leicester. Whether a wet fob is repaired or replaced is confirmed on the call.
What If the Wet Key Was the Only Key?
A car whose only key has stopped after water has no spare key to fall back on. A key that is past repair gives way to a new key, which is the work set out under replacement car keys.
Why Does a Spare Key Matter Before a Key Gets Wet?
A spare key keeps the car in use while a wet key dries, and a spare key that works places the fault in the wet key and not in the car. A second key made while one key still works is the subject of spare car keys in Leicester.
How Is a Car Key Kept Away From Water Day to Day?
Manufacturer handbooks tell owners to protect a key fob from moisture, which means pockets emptied before a wash and a dry place for the key at the beach or the pool. The wider routine for the fob, the blade and the locks is set out in the guide on how to maintain car keys and locks.
Whether your wet key is repaired or replaced is confirmed on the call.
Frequently Asked Questions
Does putting a wet car key in rice dry it?
No manufacturer handbook read for this guide names rice as a way to dry a car key, so this guide does not print rice as a method.
The sourced instruction is to wipe a wet key immediately until it is completely dry and to protect it from high temperatures, which rules out a hairdryer.
Is a car key waterproof?
No, a car key is not described as waterproof in the manufacturer handbooks read for this guide, which tell owners to protect the key from moisture and to keep it out of water and salt water.
The blade is the one part that water does not harm in the short term.
Does a car key survive the washing machine?
The blade and a separate sealed transponder chip often survive the washing machine, and the remote electronics of the key often do not.
Detergent stays inside the case and corrodes the circuit board after the key has dried.
Do you change the battery after a key fob gets wet?
A key fob battery that has been under water is often drained, and a new cell of the type the handbook of the car names restores a remote whose circuit board is sound.
One manufacturer handbook tells owners to fit only the same or an equivalent type.
How much does it cost to fix a water damaged car key?
The cost of fixing a water damaged car key is set by the part the water reached, the type of key and whether the key is repaired or replaced.
No price list is published, and a quote is agreed before work begins.