This issue’s Q&A article is about the exterior lights of your car.

Portrait of Tammy Strobel

This issue’s Q&A article is about the exterior lights of your car.

Brighter isn’t necessarily better when upgrading your car’s headlamp bulbs, even if they’re “HIDlike” halogens.
Brighter isn’t necessarily better when upgrading your car’s headlamp bulbs, even if they’re “HIDlike” halogens.


Should headlamp bulbs be replaced regularly? I have noticed, especially over the last five years or so, a huge variety of shapes and colours. It seems that white light is the current fashion in headlamps, as are wavy strips of light. Can I upgrade my car’s exterior lights to these fanciful and bright bulbs?

Automotive light bulbs, whether exterior or interior, need to be replaced only when they are blown. They do not require periodic replacement.

The current technology in lighting is LED (light-emitting diode). Prior to this, the gasdischarge lamps, commonly known as xenon or HID (high-intensity discharge) lamps, were state-of-the-art.

These gas-discharge units are still popular today, although the LED versions are fast taking over as the top choice.

The main advantage of these two technologies is their higher luminous efficiency. They consume less power compared with the old halogen light bulbs.

There are aftermarket conversion kits for the xenon-gas headlamp units, but they are costly. Also, such modifications are likely to be deemed illegal. Only factory-fitted headlamps are legal in Singapore.

Off-the-shelf LED bulbs as direct replacements for halogen bulbs are available at some accessory shops.

But before you go out and get a set for your car, make sure they are direct replacements that do not require expensive hardware and, more importantly, are not excessively brighter than your vehicle’s original headlight bulbs.

I have noticed that on some cars with daytime running lights (DRLs), the light goes off whenever the indicator on the same side lights up. But there are other cars where the DRL continues to stay on while the indicator is flashing. Why is this so?

Daytime running lights are not yet mandatory across the globe and not in Singapore either. However, many car manufacturers are incorporating DRLs as standard features, partly in anticipation of an international mandate for all vehicles.

There are significant benefits in a moving vehicle having its lights on during the day, as they enhance visibility to other road users. This is the same argument for switching on headlights in bad weather during the day – it is not for you to see the road ahead, but for others to immediately notice your presence.

Due to the natural ambient light during the day, the current generation of LED DRLs has a particularly high level of luminescence. Hence, when an indicator is switched on, the white or yellow DRL could, to the human eye, optically overwhelm the amber flashing signal.

To avoid this adverse condition, the DRL is totally turned off, so the amber flashing light appears as the only light displayed in the headlamp unit. This is the current format in lighting technology.

When DRLs first appeared on cars a few years ago, they were either halogen or regular incandescent-filament types instead of today’s LEDs, so the amber indicators were made of higher-wattage lamps to appear sufficiently brighter. With these headlamp systems, you may see the DRL and indicator flashing alongside each other.

Aftermarket DRLs are a different matter altogether. Firstly, they are not always compliant with regulations, and secondly, they may not have been designed with sufficient consideration for relative brightness. 

I have noticed that at night with my car’s headlights switched on, the engine’s idling speed slows down, while the lights stay very dim and brighten considerably only when I rev the engine. Is there a problem with the engine or the electronics, or both?

The most likely cause for the symptoms described above is a low voltage supply. This will often cause the engine control unit to function a little abnormally, causing the headlights to be dim.

The first thing to check in rectifying the problem is the condition of the battery.

If it is weak, replace the battery immediately. Sometimes, the problem may just be loose battery-terminal connections. Make sure these are clean and tight.

Another possible problem may be the earth cable, which can deteriorate over time and cause electrical issues. Inspect the cable and replace it if necessary.

Finally, check the condition of your car’s alternator, which should supply 14 volts to the battery when the engine is running at its normal idle speed.