Farmall Flat Back Lamp Replacement

ByJohn Papay

North Royalton, OH

Sealed Lamp Assembly

Remove the bezel that holds the lamp assembly in the housing and this is what you have. There is a lens, gasket and a metallic reflector. The base of the bulb comes out the back and it is threaded so that a lug wire can be attached.

Lens-Reflector Disassembly

Use a good pair of side cutters to peel back the edge of the reflector. Go very slowly and take care not to put any pressure on the lens to avoid cracking it. You will start at the bottom where there is a break in the housing and go all the away around before attempting to remove the lens.

Lens & Reflector

Once the lens is removed you can see the bulb, reflector and gasket.

Lens Markings

The lens markings read “Sealed Tractor Lamp” “Made in USA”. The word “Guide” is in the center of the lens and the word “Top” is at the top edge of the lens. It is a sealed lamp but not a sealed beam headlight. Also 4-5/8 is stamped above the word “Sealed”

Removing the Bulb

The bulb is soldered into the reflector. You will need a heavy duty soldering iron like an old American Beauty with a massive tip that won’t cool down in order to melt the solder quickly. Use rosin to help transfer the heat. Once the solder melts all the way around, the bulb will push out the front. Raise the reflector up off the table so that the bulb can drop down.

Reflector without the bulb

The old Bulb

The old bulb is quite unique. Note the unusual shape. There were no numbers on it and the voltage rating is unknown.

Old Bulb Base

What makes this bulb so unusual is the screw terminal in the base. It was decided to salvage the base from the old bulb and attach it to the new bulb to preserve the type of connection and original appearance.

Screw terminal base removed

Use a hacksaw or other small saw with a fine blade to cut all the way around the base being careful not to cut too deep. Once all the way around, the bottom should separate. The wire shown in the photos was originally attached to the base through the small hole in the wafer insulator.

New Bulb & Old Base

The concept is to attach the old base to the new bulb. This will be done after the new bulb is soldered into the reflector. The bulb chosen was the Sylvania 1156LL. The LL stands for long life and the bulb is rated for 3000 hours of operation. It draws about 2 amps and was the only commonly available bulb that would do the job. A package of 2 is available from Autozone for around $5.

Soldering the new bulb in the Reflector

Position the new bulb in the reflector and support the bulb from beneath using a shim so that it is at the right position. I wrapped a few turns of solder around the bulb to make it easier. Use rosin core solder made for electronics. Do not use acid core solder. Flux helps to make the solder flow. Once the bulb base and reflector heat up, the solder will flow nicely . Use pliers if you need to reposition the bulb.

Attaching the old base to the new bulb

Cut the wire from the old bulb and solder it to the center terminal of the new bulb. The center terminal will melt quickly so use a small iron this time. This wire will go through the hole in the old screw terminal base.

The new bulb and old base

Poke the wire through the hole in the old base and solder. This will keep the old base in place while you solder the old base to the new bulb. Again, wrap solder around the base and use the large iron to heat it up. The solder will flow all the way around and provide mechanical strength. Once cooled, clip off the wire poking through the base and file being careful to not file all the solder away.

Completed Reflector with new Bulb

Reassembly

Reassemble the lens in the reflector and orient the lens so that the top of the lens is opposite the cut in the rim of the reflector. Crimp the lip of the reflector over the lens with channel locks being very careful not to apply too much pressure and crack the lens. This is a tedious process so don’t try to do it quickly. Take small overlapping bites. The reflector is thick and does not bend easily.

Flat Back Shell on tractor

Place the ground strap over the base of the lamp and push it through the hole in the back. Attach the gasket around the rim of the reflector/lens assembly and place in the flat back shell. Place the bezel ring around the assembly and tighten.

Connect the wires

Attach the hot wire to the base of the lamp and connect the ground strap to the housing with the original screw.

Finished Product

The base of the lamp sticks out more than the original. If you want It to be nearly flush like the original you can cut the base off the new bulb and attach the old base. That’s more work and there is always a chance you’ll break the bulb. All in all it doesn’t look too bad and it sure beats a made in China Wal-Mart replacement

It Works!

The 1156LL lamp provides quite a bit of light and will be fine for most purposes. Of course you could replace these with Halogen bulbs or sealed beam headlights but it wouldn’t be very original. It’s a bit of a job but very straightforward . Just take your time and you will be pleased with the result.

The Farmall A Tractor

Farmall A, S/N F.A.A. 97951. The tractor is for Sale (Cleveland, Ohio).Contact Ed 440-213-6671