LED Lights for cars and trailers

If you own a classic car you may have thought about using LED bulbs because you heard they were brighter with less power draw on the marginal electrical system on your older car.

LED Lights for cars and trailers

You will see all kinds of claims of reduced electrical system load but a 90% power savings is often quoted. If you have a trailer that you are concerned seems to have lighting that is a bit dim, you may have considered getting LED lights for the rear to improve rear visibility at night and when braking and turning.

I had heard about LEDs as the answer to all these problems and have tried some different LED solutions with mixed success so I wanted to take a minute and tell you about those experiences to save you some money and time.

The first time I purchased some LED bulbs in an auto parts store I was disappointed to find out that they had less light output than a stock bulb. LEDs have several advantages but light output is not one of them, at least not in a standard LED replacement bulb situation. When I took them back into the store to complain to them the clerk admitted that I was not the first person who had noticed they were not as bright as the standard bulbs. Also, the texture of the lense can reduce the efficiency and output of LED bulbs. There are exceptions to the light output issue and I’ll cover those in a minute.

If the bulb mounts on a stock base and has a small number of LED like about 6-12 LEDs mounted on the base that is about 1 inch in diameter, it is probably going to be less than or equal to a stock bulb’s brightness. The LED bulb’s big advantages are low current draw, extended life and cool operating temperature. The LED’s big disadvantages are they may cause your turn signals to work incorrectly or cause your cruise control to stop working. More on these issues in a moment... 

Multi bulb arrays

If you are looking for brightness the larger 1.5 + inch multi bulb arrays of 30+ bulbs these will indeed give you more output. Many of these larger array type bulbs won't fit the stock bulb holder without some modifications but they are the way to go if you are looking for lots of visibility. Most stock bulb holders only have enough clearance to slide the bulb through the opening. Usually you have to modify your housing to accommodate these array panels and you may have to hard wire the bulbs to the wiring harness on your car as they will generally come with wire leads and not a bayonet base attached. Another type of multi bulb unit you will see offered on eBay are light sticks and these can be used in several different areas.

Some are flexible and allow some bending. The can have multiple circuits in the array so that running lights, turn signals and brake lights can all be accomodated into a single LED stick. For the classic car enthusiast we often have to balance appearance and originality with safety. Using LEDs in a creative and tasteful way for center brake lights, license plate lights and other safety lights can give you much improved rearward visibility.

Thermal flashers

If your car has a thermal type flasher unit it relies on current draw to function properly. With LEDs the draw is reduced and there may not be enough draw to make them flash at all. If you leave the front turn signals with regular bulbs and the rear with LEDs, this may solve the problem or you can fit a load resistor.

These are sometimes sold by the same vendors that sell the bulbs. The load resistor can get hot and be sure to follow the instructions carefully on their installation. Also, if you are fitting LED lights to save on power, the load resistor defeats that purpose and adds back in drain that the LED saves. Another option if your turn signals flutter too quickly or don’t work correctly is to install a heavy duty flasher unit. These are usually non-thermal and will flash no matter what the load. They may be labeled “LED compatible” or “for trailer towing”.

Another flasher unit that has gained some popularity are center brake light modulators. We have all used the trick of pumping our brakes to make the brake lights flash and warn other drivers that we are stopping. A center brake light modulator unit essentially does this for you by flashing the center brake light for you when you apply the brakes.

Depending on how the unit is made it may flash the brake light a few times and then go to a constant on mode and some will have a delay timer so that if you are in stop and go traffic and are on and off the brakes it will keep the light on constant until a certain number of seconds have passed. Kahtec flasher units are the ones I have used but you will find numerous other brands.

Cruise Control Issues

Another thing to be aware of on modern cars is that the cruise control on many cars uses the presence of ground coming through the incandescent bulb to allow the cruise control to activate. When the absence of ground is sensed, the cruise control cuts out as it indicates the brake pedal has been pushed. With the LED bulb there is not enough resistance in the bulb so the cruise control never turns on as it senses the brake is always depressed.

Many new cars have dash indicator lights that show when you have a burnt out bulb. These indicator lights may be triggered by the use of LED lights, as again, the LED bulbs are not sensed but the detection circuit.

Trailer lighting

We have all imagined the horror story of someone plowing into the rear of our trailers and it is not a pretty picture to think about the damage to the trailer and the tow vehicle along with the trailer’s precious cargo. I have fitted the trailer LED Brake/Turn Signal light units (not bulbs but the unitized LED units) on my trailer and these are incredibly bright. I would highly recommend these. Visibility is excellent day or night.

Other ways to get more light output

I have found another inexpensive way to get more light output is to fit a 2357 bulb in place of the more common 1157. If your system uses 1157 dual filament bulbs you can use the 2357s. They fit the housing with no mods and are brighter but have a slightly shorter life.

Another way to get brightness is by using halogen bulbs. The problem with halogen and some of the other bright bulbs is they indeed run hotter and can melt the plastic parts or the lens in the taillight housing. If you decide to use a hotter bulb be sure to carefully test the bulb/housing combination. Remember that if you had the headlights on and applied the brake lights over a long period of time, like on a long downhill coming out of the mountains, the combined heat from both filaments can get it very hot and start melting things.