A car contains the gauges, warning lights, and other notifications that a driver needs to drive the vehicle safely and correctly. So what do you do when these gauges go crazy when you try to start the engine? We've compiled the information to help you out below.
If the gauges and warning lights go crazy when you try to start the car, then the instrument cluster is not receiving the electric current that it needs.
In this scenario, you may try checking the following:
- Loose battery connection
- Discharged battery
- Faulty alternator
- Bad wiring and grounding
- Faulty ignition switch
- Failing voltage regulator
- Faulty ECU or BCM
- Bad instrument cluster circuit board
There may be many other reasons when only specific gauges act up when the engine is already running.
However, if the problem occurs only during engine start-up, we can isolate the issue to the above sources.
Are you experiencing this problem in your car now? Perhaps you encountered this problem previously, and now you want to know how to fix it in case it happens again. Either way, read on because you're in the right place.
Why Do My Gauges Go Crazy When I Start My Car?
Like most electronic equipment, your car's instrument panel will function properly if it receives a continual and precise flow of electricity. Otherwise, the cluster's gauges and lights can flicker like crazy.
The instrument cluster houses the information you need to safely and properly drive your car. It monitors your speed, engine RPM, fuel, brakes, lights, and many more.
Undoubtedly, it is an essential piece of equipment.
Because the instrument cluster monitors many things in the vehicle, we know that it also connects many car sensors. In short, there are several possible causes of erratic gauges and lights.
However, if the gauges and lights go crazy only when you try to start the car and go back to normal after the engine runs typically, then we can limit the suspect list to a few possible culprits.
Checking A Car's Battery Terminals
Before checking for any faulty components in the instrument cluster's circuits, we should try checking the more simple possible culprits: the power source. Turn off the car and check the car battery.
First, you might want to check the battery connections. Are the terminals dirty or corroded? Bluish-white powder on the terminals means battery chemicals may disintegrate your terminals slowly.
Battery terminal dirt and corrosion can cause poor connection and drain the battery's charge faster. You should remove the cable connectors and clean the terminals.
You may want to use a small brush, a simple baking powder, and a water solution to clean the terminals. Make sure to reattach the clamps securely to the terminals after cleaning.
Over time, corrosion may wear the terminals down. If the terminal clamps are still loose after tightening the bolts, you may want to try placing a battery shim on the terminals before reattaching the clamps.
Testing The Battery And Alternator
After ensuring a proper battery connection, you should test the battery's charge and state of health.
A dying battery can cause your car's electromechanical parts to act weirdly. Moreover, a weak battery charge is a probable suspect if your gauges go crazy while you're having a hard time starting your car.
You will need a multimeter or a battery tester to test your car battery.
Test With A Multimeter
A multimeter is an electronic device that measures the voltage, amperage, and resistance of different parts of an electrical circuit. In this case, we will be testing the electrical source, which is the battery.
To test your battery with a multimeter, follow these easy steps:
- Set the multimeter's DC voltage to 20 volts.
- Connect the red probe of the multimeter to the battery's positive terminal.
- Connect the black probe of the multimeter to the battery's negative terminal.
Battery Resting Voltage - Multimeter
A fully-charged battery's typical "resting voltage" ranges from 12.6 to 12.9 volts. When your car's engine is off, you should get this resting voltage reading.
Use the following voltage guide as a reference.
- 12.6V volts or above: Fully-charged battery
- 12.5 volts - Good battery charge; sufficient for easy engine starts
- 12.1 - 12.4 volts - Partially discharged battery; some difficulty
- 12.0 volts or below - Discharged battery; needs immediate recharging
A deeply discharged battery can cause erratic behavior in your car's accessories, especially when starting the engine. During ignition, your vehicle will divert most of the battery power to start the car.
Battery CCA - Multimeter
Aside from voltage, you need to test your battery's cold-cranking amps (CCA) rating. In layman's terms, CCA values describe the battery's engine-starting ability during cold weather.
Passenger cars, SUVs, and light trucks need between 400 and 600 CCA to start the engine. On the other hand, full-size and heavy-duty vehicles may need 800 to 1,000 CCA to get their engines running.
Although multimeters cannot read CCA ratings directly, they can help you estimate the value. To do this, you need to connect and see your multimeter's DC voltage reading while trying to start up your engine.
During engine cranking, the voltage reading should drop temporarily. For fully-charged batteries, the voltage should not read below 10 volts.
If the reading is too low, your battery needs a replacement or recharge.
Battery Voltage With Engine On - Multimeter
Finally, you need to test your battery's voltage during engine operation. At this point, the battery should no longer be your car's primary power source. Instead, the alternator takes over this role.
After the engine starts, a good car battery should have a voltage reading between 13.7-14.7 volts. The battery's voltage reading exceeds its resting voltage as the alternator recharges the battery.
Car Battery Tester
Car battery testers or analyzers have more battery-specific features than a standard multimeter.
Aside from giving out the battery's voltage reading, testers also analyze the battery's state of health, CCA, and state of charge.
Here are the steps to use a car battery tester:
- Attach the red battery tester probe to the positive terminal of the battery.
- Attach the black battery tester probe to the negative terminal of the battery.
- Choose your battery type from the tester's menu.
- Absorbent Glass Mat (AGM) Flat Plate
- Regular Flooded
- Gel Type Battery
- AGM Spiral
- Enhanced Flooded Battery (EFB)
- Choose your battery's CCA rating (you may find it on the battery's label or manual).
- Start the testing process and wait for the results to appear on the tester's screen.
Most battery testers will show the following results:
- State of charge
- State of health
- Actual against rated CCA
- Overall diagnosis - e.g., Good, Replace, etc.
Car battery testers may also perform charging and cranking tests.
A cranking test shows the cranking voltage and how long it takes for the engine to start. Alternatively, a charging test shows the battery's voltage level while the engine and the alternator are running.
Both the cranking and charging tests should also display an overall analysis at the end.
See this informative video below on how to use a car battery tester:
Alternator Test - Battery Tester Or Multimeter
If your tester shows that you have a discharged battery, then it can mean at least one of two things below:
- The battery is old and cannot hold a charge.
- The alternator is faulty and cannot charge the battery correctly.
An easy way to know whether your problem is with the battery or the alternator is through the tester's "Charging Test." Do the following steps below to run this test.
- Start the engine and turn on all the car's standard electrical equipment - headlamps, air conditioning, radio/multimedia system, etc.
- Choose "Charging Test" from the menu. The test will give you a precise result, e.g., "low," "normal," or "good."
Alternatively, you can also use a multimeter to test the alternator. While the engine is running, you should connect the multimeter to the battery terminals.
The voltage reading should not drop below 13.5 volts.
If the reading is below 13 volts, your alternator is not generating enough electricity to charge the battery.
How To Check The Cluster's Circuit For Bad Connection
Suppose your gauges' problem is not with the power source (battery and alternator). In that case, it must be along the electrical path (wires, switches, and controllers) or the destination (the instrument cluster itself).
Here are some components that may cause gauge problems during ignition:
- Chafed, exposed, or loose wiring to the instrument cluster
- Improper grounding
- Faulty instrument cluster voltage regulator
- Bad contact points on the ignition switch
- Failing electronic control unit (ECU) or body control module (BCM)
- Deteriorated sections on the instrument cluster's printed circuit or circuit board
Detecting auto electrical problems is no easy task for an average car owner. However, some enthusiasts may be able to fix the instrument cluster's issues with a multimeter and some soldering work.
If your gauges and lights go crazy during ignition, you have an inconsistent electrical supply to your instrument cluster. Faulty components can cause this in your cluster's electrical circuit, like your battery, alternator, wirings, voltage regulator, or switches.
You may test, repair, and replace these parts independently if you have auto electrical experience. However, average car owners may be better off with help from an auto electrician or the dealership.
Thank you very much for reading. We hope we were able to help you identify and solve your problem with malfunctioning gauges.
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