When your car has trouble starting, one potential culprit is the starter relay. It’s a small yet vital component in your vehicle’s ignition system.
While not as commonly discussed as the battery or starter motor, the starter relay is crucial in ensuring your engine cranks when you turn the key or press the start button. In this guide, we’ll explore what a starter relay is, how it works, signs it’s going bad, how to test it, and what to do if it fails.
What is a relay? How does it work?
A starter relay is often mistaken for the starter motor solenoid. In casual conversations, they are usually used interchangeably. However, although they are closely related, they are two different components, hence the confusion.
A starter relay acts as an electrical switch that controls the high current intended for the starter solenoid. Every time you start your car, there’s a small current that flows through the ignition circuit to the relay. The relay then closes the circuit and allows a larger current from the battery to pass through to the starter motor. This then turns the engine over.
The relay is the middleman between the ignition switch and the solenoid. It’s usually found in the fuse box or somewhere along the wiring, not directly in the starter motor.
Signs of a faulty starter relay
Pinpointing a bad starter relay is tricky. The symptoms can be identical to those of a faulty starter motor. If you notice these signs, it’s best to look at your starter relay, as your starter motor may work fine.
- Clicking Sound But No Crank: There’s a subtle clicking sound, but the engine won’t crank.
- No Sound at All: Your relay is not activating if you don’t hear any sound. Be it a clicking or cranking noise.
- Intermittent Starting Problems: Sometimes your car starts fine; other times, it won’t. This could mean the relay is failing sporadically.
- Starter Stays Engaged: A bad relay can force your starter motor to engage continuously, even when the engine is already running.
- Burning Smell or Smoke: A shorted or overheated relay can produce a burning odor or visible smoke.
Is your car registering one or more of these symptoms? If so, it’s best to have your relay tested or replaced.
What causes a bad starter relay?
A starter relay can serve you up to 5 to 10 years based on their expected lifespan. This usually translates to around 100,000 miles or more. Still, your relay can break down earlier.
Here are the reasons that may cause that:
Heat and Vibration: Your relay’s internal contacts are susceptible to premature breakdown if they are subjected to constant high temperatures and continuous vibrations.
Corrosion: Moisture is the natural enemy of any electrical component. This often leads to corrosion on the terminals, ruining the electrical connection.
Electrical Overload: Surges or shorts in the circuit can fry the relay’s internal components.
Wiring Issues: Loose or frayed wires can interfere with current flow, leading to erratic performance or eventual failure.
How do I test a starter relay?
Testing a starter relay isn’t as complicated as you may think. If you’re ready to get some dirt on your hands, these DIY methods can help you test your car starter relay.
- Relay swap test
This is probably the easiest way to test. All you have to do is swap your starter relay with one with the same part number and start your car.
Find your fuse box under the hood. Remove the suspected faulty starter relay and swap it with the one for the horn or AC. After swapping, restart your vehicle. If it starts without a problem, then your old starter relay is bad.
- Multimeter Test
If you have a multimeter handy, this is another reliable way to test your starter relay. Start by removing the suspected faulty relay from the fuse box. Set your multimeter to measure resistance (Ohms), then check the resistance between the coil terminals. These are usually marked 85 and 86 on the relay. Your reading should fall between 50 and 200 ohms if your relay is healthy.
Next, 12 volts are applied to the coil terminals (85 and 86), and the continuity between the switch terminals, usually marked 30 and 87, is checked. If there’s no continuity when voltage is applied, the relay is bad and should be replaced.
Conclusion
A starter relay is critical for your car’s smooth ignition. But like any electrical component, it can break down prematurely. Once it goes bad, it’s practical to just replace it.
DIY tests and replacement remain the best option to avoid additional charges. Buying a new one isn’t expensive, and replacing it wouldn’t even take an hour.
Common questions about starter relays
1. Will a bad starter relay drain my battery?
Not really. A faulty starter relay typically won’t drain your battery unless it’s stuck in the “on” position, keeping the circuit closed and drawing current even when the car is off. That’s rare but possible.
2. How do I know if it’s the starter relay or the starter motor?
Start by listening: It could be either if you hear a click but no crank. Try a relay swap test or multimeter test. If the relay is good and you still get no crank, the starter motor or solenoid may be the issue. Look for signs that the starter motor is bad.
3. Can I still drive my car if the starter relay is bad?
No. Your car won’t even start if your relay has completely failed. Although, in some cases, you can still jump your relay or start with a remote switch, this solution is just temporary. It’s always best and practical to just replace this inexpensive part when it goes bad.
4. How much does it cost to replace a starter relay?
Replacing a broken starter relay wouldn’t hurt your pocket; it’s a relatively cheap component. A new one costs between $10 and $50. However, the cost can add up if you let a mechanic replace you.
5. How long does a starter relay usually last?
It depends on several factors. However, starter relays are expected to last 5 to 10 years. They can fail prematurely, though, due to heat, corrosion, wiring problems, and electrical overload.
6. Can I test the starter relay myself?
Yes. Testing a starter relay is straightforward enough for a DIY test. Your most common option would be to test with a relay swap or multimeter. Doing a DIY test can save time and money instead of taking your car to a mechanic shop.