Seemingly as small as it is, the role of a vehicle’s relay is irreplaceable.
It controls and manages the high-voltage current from the power source to every other electricity-driven component, ensuring a smooth, bumpless operation for your car.
Hence, a relay clicking when car is off cannot mean something good, and the last thing you want to do is to ignore it.
Keep scrolling through my guides to learn the possible reasons and viable solutions.
Why Is The Relay Clicking When Car Is Off?
The relay clicking constantly can only mean at least one of the following: dead batteries, faulty relays, computer failures, and ground wire or power supply resistance.
Dead Batteries
Relay fuse box clicking sounds likely stem from the starter solenoids and their lack of battery power.
Worse, your car might even shut off mid-drive, indicating the alternator refuses to charge the system.
Observe the car’s run and engine compartment to confirm the issue.
If the vehicle cannot reach beyond 10 MPH or suffer from high-density smoke from the engine, your system voltage and wiring problems clearly need instant treatment.
Faulty Relays
Of course, another reason behind clicking noise from fuse box when trying to start car is the technical errors within the relay itself, which necessitates a starter relay bypass.
A relay breaking down cannot shut off your secondary circuit properly.
It will try and try again after the vehicle powers down – to no avail, since the mechanism has already got stuck.
These failed attempts to break off the circuits result in repeated, loud relay sounds.
Several possible reasons are cited for a bad relay. Some of the most common are:
- Contaminations in the car’s moving parts
- Mechanical wear
- Electrical overloading
- Worn or corroded contacts
- Short-circuits
- Overheating, even after changing the water pumps and thermostats
Computer Failure
Why is my fuse box clicking? One should not completely rule out the possibility of a malfunctioning PCM or ECU.
Their combined design takes charge of numerous automobile systems and functions – and that includes the relay itself!
In modern vehicles, the ECU compartment controls and communicates with varied components via electrical signals.
As such, when this ECU encounters malfunctions or technical faults, the relay will receive erratic or incorrect signals, causing rapid on/off clicking.
Even when the car has already been turned off, the issue will linger due to the ECU’s residual power.
Ground Wire Resistance for The Relay’s Control Side
With extremely weak ground connections, there is no way the relay coils can receive enough current for full-scale energization.
As a consequence, the coil’s generated magnetic field fails to hold consistent relay contacts in their activated positions and keeps cycling between deactivated and activated states.
No wonder you have to suffer from all those relay clicks but no power.
Power Supply Resistance To The Relay’s Control Side
Needless to say, power supply malfunction impedes the current flow.
This sudden resistance causes a massive voltage drop throughout the circuit and reduces the voltage transferred to the relay.
With lower voltage, the car’s relay coils do not have it in them to achieve optimal energizing and struggle to hold the activated relay contacts.
The constant, disruptive disengagement and engagement eventually lead to rapid clicking noises.
How to Fix Clicking Relay?
There are some simple, powerful tips even beginners could adopt to return their clicking relay to their regular, functional state:
Clear the Terminals or Jump Start The Car
First, try clearing the relay’s terminals. This method ensures no technical issues with the relay’s connections, eventually erasing loud noises.
And if that does not work out? Consider turning to the classic “jump start’ strategy, which involves removing the car’s starter relay and using a 12V power source to “jump” it.
As a result, the relay will be bypassed, sending direct power to the car’s starter monitor.
Here are the easy steps to jump-start your vehicle:
- First, disconnect your battery’s negative terminal. Once done, remove the car’s relay from its position completely.
- Next, link one jumper wire end to the battery’s positive terminal. Then touch the remaining end of that wire to the relay’s “S” terminal.
- Finally, pick another jumpering wire and connect the relay’s “I” terminal to the battery’s negative terminal.
Your success with this “jump-start” method implies both great and bad news. The great news is that you do not have to get stuck in the middle of an empty road with no repair shop nearby.
And the bad news? Your starter relay clearly needs replacing!
But if the method doesn’t work for you, something else is happening inside the starter system, such as a faulty ignition switch or motor.
What If The Relay Clicking Still Continues?
In that case, either fix the motor/starter switch or – well, prepare for it – replace the entire starter relay. I will discuss the detailed steps in the next section.
How to Replace The Starter Relay or Solenoid If It Cannot Be Fixed
Step 1. Park your vehicle on an even, solid surface.
Accessing the vehicle’s starter would be much easier if you could find a good surface to support the car’s weight (and the jack stand as well, which I will discuss in the latter steps)
Step 2. Disconnect the car’s battery.
Before proceeding with anything, you must disconnect the car’s power sources to prevent electrical damage and shock.
Simply use a socket wrench or your own hand to slacken the battery’s negative terminal and slide it from the terminal posts.
Step 3. Jack the car up if necessary
Does the starter require underneath access?
Then I suggest sliding a trolley or scissor jack beneath the car at its prefixed jack points. Turn or press the handle to jack the vehicle up, and stop when you think it is high enough to work with.
Step 4. Place the jack stands under the car.
Never work under a car until it is properly supported by a good jack stand. Can you imagine what would happen if the car came crashing down while you were directly underneath it?
Slide the jack stands underneath the designated jack point, then slowly lower your car onto it. Ensure the car stands properly and feels steady.
Step 5. Find the starter
Starters and starter relays are often attached, usually located on the bell housing of the transmission (where the engine and transmission interconnect).
Check this guide if you can’t find this part on yours.
Step 6. Mark the starter’s wires
The small cylinder linked to the car’s starter is the relay – from which three wires keep sprawling to touch their respective terminals.
Use different masking tape pieces to mark every wire and its terminal:
- One wire is at the top or far from the automobile starters
- Another at the bottom or closest to the starter
- The last is a wiring pigtail you can connect at one place only
Step 7. Disconnect the wires and remove compartments.
With all the wires marked clearly, start disconnecting them from your starter relay. Once done, move on to uninstall the mounting bolts and the relay itself.
Step 8. Slide in your new relay.
Slide the newly-purchased relay into the housings (from which you have just removed the old relay). Apply more pressure to push the plungers into the slot properly.
Step 9. Secure the screws and wiring.
Insert the screws and bolts to secure your new relay to its spot. And lastly, use the marked labels on the wiring systems to connect each wire to the relay in order.
Congratulations! The starter relay has been successfully swapped.
What Will Happen If I Do Not Fix or Replace The Relay?
Brace yourself for these dreading issues if the relay clicking with key off does not get fixed on time:
Component Failure
The relay and starter system plays a major role in electrical current flow control in cooling fans, headlights, fuel pumps, and more.
Needless to say, all these components will malfunction or fail altogether should anything undesirable happen to the relay.
For example, imagine what would happen if the fuel pumps struggled to deliver engine fuel. Your car would get stuck with the ignition or even stall mid-driving.
Electrical System Problems
A relay that remains engaged/stuck in the close position may create a constant, exhaustive circuit that drains the car’s batteries when the vehicle is already off.
Drained or dead batteries are only a matter of time, leaving you stuck and stranded!
Safety Concerns
As previously mentioned, the relay takes charge of brake lights or headlights as well.
It does not take a genius to piece two and two together and guess what would happen if these lights do not activate.
Both your road safety and nighttime visibility will be severely compromised, paving the way to deadly, hazardous situations.
Conclusion
No sane owner would ignore the relay clicking when car is off – unless he wants to invite accidents and car collisions!
Double-check whether the battery, ECU, power supply, or the relay itself is at fault, and try out my tips above to fix it back to normal.