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Be confident fitting HID bulbs

By autotech-nic on February 4, 2016

High Intensity Discharge (HID) headlamp bulbs, also known as Gas Discharge or Xenon bulbs, have steadily increased in usage across the automotive market. Yet for mechanics and technicians they are sometimes a misunderstood product, referred to as ‘scary and expensive bulbs’.

To provide clarity and improve confidence in fitting HID bulbs, Ring explains what a HID bulb is.

What is a HID bulb?
The obvious difference is that HID bulbs have no filament. Instead, there is a glass capsule in the centre of the bulb containing Xenon gas. Two metal electrodes going into the glass capsule enables a high voltage pulse to cross the Xenon gas in an arch shape. This voltage ignites the gas to produce a bright white light output. This is very similar to how fluorescent tubes work.

The bit that puts mechanics off is the start-up voltage that pulses across the Xenon gas to form the arch. This voltage has to be very high, typically up to 24,000 volts. A ballast is required for each headlamp. These ballasts convert the vehicle’s 12v DC voltage into 2,400v AC to ignite the bulb and then maintains a lower operating voltage. The operating voltage is 85v for D1 and D2 HID bulbs and 42v for D3 and D4 HID bulbs.

HID bulb


Clearly this high start-up voltage can be potentially hazardous. Following safety instructions, HID bulbs can be fitted perfectly safely.




Types of HID bulbs
There are four cap type references of HID bulbs; D1, D2, D3 and D4. These all come with a suffix of either ‘R’ or ‘S’ eg. D1R or D1S. Bulbs with the suffix R are designed to work in Complex Surface headlamp units. Bulbs with the suffix S are designed to work in Projector headlamps.


Reflector headlamp

Projector Headlamp

Projector headlamp







All HID bulbs must be fitted with a direct replacement. So if you remove a D2R HID bulb it must be replaced with a D2R HID bulb.

D1 and D3 bulbs have the ignition/starter pack fitted to the bulb. D2 and D4 bulbs do not. The ignition/starter is combined with the ballast.

D3 and D4 bulbs are recent additions to the range; they are designed to work with new compact ballasts and are already being fitted to Audi, BMW and Lexus models. They contain less mercury, so have better eco friendly credentials. They also run at a lower voltage of 42v once operating.

RIng HID bulbsHID bulbs and HID headlamps systems are only street legal if the bulbs being fitted are E marked and fitted to cars that have auto levelling, to prevent dazzle and a wash/wipe to prevent the light scattering from dirt on the lens.


Benefits of HID Bulbs

HID bulbs are up to 3x brighter than a halogen bulb, they also have an incredibly long life, averaging around 2,500 hours of use.

HID bulbs have higher luminance than Halogen bulbs, normally 3,200 lumens.

The colour temperature is 4,100oK, producing a crisp white light output close to daylight.

The high start-up voltage is potentially hazardous and is understandably the main concern for mechanics but rather than refer the owner back to a main dealer, by taking simple steps, you can change HID bulbs safely.

* The first thing to do is isolate the light circuit. Turn off the ignition and headlight switch.

* Isolate the headlamp circuit by removing the relevant lighting fuse. (Check the handbook to locate the correct fuse).

* As an additional precaution, leave 5 minutes for the bulb to cool down. HID bulbs run at very high temperatures so it is worth giving them time to cool down.

* Then proceed to change the bulb as you would do a normal headlamp bulb. Remove the bulb cover. Unplug the bulb connector, then remove the HID bulb, replacing it with the same reference type.

* Once the bulb has been replaced, reverse the fitting process remembering to re-install the fuse.

It has always been important to replace bulbs in pairs. With HID bulbs it is key; HID bulbs should be replaced in pairs to ensure a colour match and consistent light output.

Fitting HID bulbs: It all starts to add up
The benefit to mechanics for fitting HID bulbs is twofold. Firstly, they are not losing a customer to a main dealer or another garage that can replace HID bulbs. Secondly, fitting HID bulbs increases a garage’s sales margin.

Cost of replacing two H7 at retail prices is £18

Cost of replacing two HID bulbs at retail is £199.

By just replacing two HID bulbs, the additional revenue is £181.

Ring has also produced a fitting guide for extra support. Contact you nearest Ring Stockist for more information.




About Autotechnician
Autotechnician is a magazine published nine times a year, delivering essential information to independent garage owners and technicians in the UK. Delivered both digitally and in print, autotechnician provides readers with technical, training, business advice, product and news, allowing our readers to keep up to date with information they need to run and work within a modern workshop.
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