LED Head Light Conversion


Two 7″ round domed headlights.

Pair of LED H4 fitting headlight bulbs.

What’s in the pack:

Headlight lenses and two sets of bulbs were supplied to me by Mustang Maniac The cost of which are yet to be advised. Obviously only one pair will come with the kit if Mustang Maniac goes ahead with the kits.


It’s common knowledge that lights on classic cars are not great. Technology moves on and a significant upgrade of Halogen saled bulbs for the Mustang and other 7″ bulbs users has certainly helped to improve things. Replacement bulbs are like the originals and are of the standard ‘sealed beam’ style which I had refitted back in my car with correct Ford logo lenses.

These are the proposed replacements with optional side lights.

The side by side comparison of both bulbs, Ford on the left and the proposed replacements on the right.

The replacement halogens looked great and provided a nice upgrade compared to the fillament ‘candle’ power of the originals. However five years ago LED bulbs were very expensive and nowhere near as widely available as they are now. I still love the stock look, many of the LED option headlights are clear or the resto mod halo style, which in my opinion takes away that classic car look.

All the lightbulbs on my car are LED, and I just wanted that super white look on the headlights and of course the increased night vision and visibility to other road users.

Adam has been doing some homework at my request to see if there was a classic car look with with LED upgrades. He had a few options and and asked me if I wanted to be the test rig as it were. I jumped at the chance and this is that trial fitting and testing.


Removing the headlight.

The headlight doors are held in place by four screws, one in each corner.

The headlight door is not attached to anything and can be lifted off cleanly.

With the door off the headlight retaining ring becomes visible which in turn is held in place by three screws. Removing the threee ring screws will release the glass and could fall out if you are not careful.

With the ring off it was an ideal time to give the brightwork another polish and clean up before being refitted. Metal polish applied and buffed to a shine. I was surprised just how dirty they had become.

Lift the bulb towards you to expose the wire loom fitting behind the bulbs. Disconnect the plug fitting and the sealed bulb unit will come free.

The main problem is that there is a clearance issue behind the bulb. With the sealed beam and fitting plug in place there is just a few millimetres at most.

The Headlight Options:

This is split into two sections in effect, the lenses and the LED bulbs themselves.

The Bulbs:

There are many options of bulbs. Most of the high power LED bulbs will need to have some sort of cooling. That may be provided by the use of built in mini fans or heatsinks. The passive heatsinks are predominantly bigger and will definitely not fit behind the bulbs.

Active bulbs have a fan which will extract the heat produced from the LEDs over the cooling fins thus enabling the LEDs to operate properly and last as they are intended to do so, 30,000 hours or just under three half years in this bulb set case.

Here you can see the comparison of bulbs. The standard length of the H4 bulbs on the left and the LED option on the right without any excessive heatsink. The blue LED much larger base contains a small fan built within it and is considerably shorter than some other LED fan options available. Even so, the additional 10mm longer, plus the loom fitting causes the problem of clearance at the back of the bulb when test fitted. It was worth the try and would have been a very neat option. This was the “it could fit” option, but these will not fit as they are. Yes you can cut the connector of and make individual blade fitting but that is a real pain and will still be very close the fender fronts and not recommended.

The other option of bulbs to try still has the fan and heatsink. In order to make this style fit a wire pigtail will plug into the loom fitting and not plugged in directly behind the bulb itself. Not as common, but a very nice alternative. Also with LEDs there is an option to customise the colour of light from the LEDs. These are the 6000k option which gives a very clean white light, very much like the HID bulbs. Of course the 3000k or the 4000k options will give the more standard filament bulb warmer look. These are the they “will fit” option.

With the additional pigtail connection this means that the bulb body can be longer itself without being a problem. Below is the longer fitting bulbs compared to the other already too long option in blue. Although the bulb is even longer the net length is shorter as the fitting is held away from the bulb itself via the pigtail. The pigtail and loom connection will tuck neatly behind the bowl at the back. Comparison of the bulbs getting longer left to right., Halogen, all in one, and the pigtail variation.

Bulb Power:

The power of a bulb is rated on its output power known as Lumens or ‘lm’ suffix.

– Halogen standard bulbs are rated at 1000 to 1500lm. Although some bulbs can be tweaked to give more, but are much more expensive than their standard counterparts.

– The blue LED bulb has a rating of 12000lm total which is 6000lm each side.

– The pigtailed version is rated at 10800lm total which is 5400lm each side.

Thus the LED giving off considerably more light than the halogen, more on that at the end with comparison shots. Supposedly these LEDs are 300% brighter. I don’t think it’s near that, but they are certainly much, much brighter.

The pigtailed bulb has a clever fitting for the sprung loaded fitting or the normal H4 recess cut out. The LED bulb twists out via bayonets and allows the plate to be swapped over for both style of fittings as required. A nice touch by the makers.


There are a number of options I mentioned earlier such as, clear lenses semi patterned or patterned. There are variations of these themes with built in side lights or no side lights.

The option I have here is the pattered type lenses with the side light option. The lenses come with a dust cap, pre fitted H4 halogen bulb and sidelight.

Standard clip to remove the halogen bulb.

The sidelight option is removed by pulling from the snug fit grommet and is a standard BS9s filament bulb.

As I have LED/indicator side lights at the front this additional sidelight isn’t required at the moment, so I removed the bulb and will be blanked. I may refit the bulb later if I get the urge as long as it’s an LED alternative of course.

Measuring the height of these replacement lenses the standard 6″ depth with the longer bodied LED (blue) bulb is past the limit with the loom fitting plug in place. Verified by a test fitting.

Sidelight Options.

You can leave the sidelight in place and use it, or blank it off. I did the later using the original grommet and slightly smaller blank off grommet inside the other hole to fill.

In order to avoid the black plug which can be seen through the glass I decided to spray them with a little left over chrome car spray I had left over.

The results were good enough and can just bout see them. The pic on the left is the hole exposed and the right is blanked off.

Fitting The LED Bulbs:

Test fitting of the pigtailed LED bulbs showed that the dust cap will not allow the bulb to be fitted with the dust cap in place as the bayonet fittings are covered up.

The answer is to turn the dust cap inside out and cut back the additional internal collar with a sharp knife, I used a scalpel and a new blade. When the dust cap is reverted back to the correct orientation it clears the bayonets fine.

Note: Before cutting the dust cap I did test fit the lens and the bulb together fitted back into the bulb bowl, there was enough clearance to allow the air flow at the back for adequate cooling.

Another reason the bulb plate is removable because the spring loaded clips will not bend around the motor and heatsink. Clip the plate in place first without the main body of the bulb. (Test fitting of the bulb without the dust cap in place is shown in the larger picture).

Now the clever bit; place the dust cap over the bulb and insert the LED main body into the base plate and twist the bulb until it clicks in place. You can see from the Picture here below that there is space around the bulb for the heat exhaust.


To align the beam pattern which is so much more visible now, the LEDs are to be facing 9 – 3 orientation, or the centre of the flat bulb vertical. You may need to adjust this angle once the bulb is fitted back in place and to then checking the aim of the lights as well.

Refitting the Headlight

Clip the loom connector to the pigtail.

Move the headlight back into the mounting bowl and thread the wiring to the back of the headlight bowl.

The headlight has three ridges which sit within the headlight bowl to stop it twisting and moving the headlight pattern. Seat the headlight in place and fit the retaining ring onto the lens and tighten up properly when all is held in place.

Check the headlight aim and all is working correctly.

With everything working and in its correct place refit the headlight door.

Time Taken:

In theory it should take around half an hour to replace a headlight bulb each side.

However as I was trialling different bulbs and to see what fitted it took me longer. Of course I won’t add that to the overall time as I have done the working out for you. The only non standard part is the trimming of the dust caps to allow the LEDs to locate in the holding plate. That only took a couple of minutes to do it neatly with a sharp knife. Alignment of the bulb within the lens is the only bit to remember before final screwing up.

Full time took around forty minutes all in for each side.


I pushed the car out of the garage a bit and shut the door to keep out much of the light as I could. I changed the driver’s side first in order to give the comparison. Left pic the original halogen, the right pic the LED bulb.

The results on the wall test looked very noticeable as well. The left side of the pic is the LED shows very white. The right side shows the warm light of the halogen and not much light pattern definition.

With both LED bulbs fitted.


This is a great upgrade and will certainly help with the nigh time running and visibility to other road users or in poor weather. A very modern upgrade that doesn’t look out of place. Less strain on the alternator regarding power draw is a major advantage as well.

Is there a downside?

Only if you want to be picky! With the engine of and the headlights on, there is a very faint hum of a motor which comes from the back of the LED bulbs. With the engine on you will never hear it. In the open you can hardly hear it, but if you listen for it you can hear it – just. The motors are ball bearing based and designed for long. I would say that it’s kinda cool that I have cooling fans for my LED headlights on an old classic car!

Share my Content