Heinze coil box restoration
Posted: Sun Feb 15, 2026 10:05 am
This Heinze coil box came in for lid repair. There was a chunk of wood missing on one side. I also noticed one of the contact springs was loose, then broke off.
During the spring replacement I noticed a lot of corrosion around split rivets that hold the springs (see photo) and wire that carries power to the coils. Measuring the resistance on each spring contact revealed one contact had very high resistance, it was measuring 68k ohms. This would essentially stop the coil from working since very little current would get into the primary coil. The other contracts measured 1-3 ohms, this resistance will have a negative effect on coil performance.
So although this coil box would have four rebuilt coils they all would perform poorly due to the resistance inline with the primary coils. I believe this is a bigger issue than owners realize. Most coil boxes are still running with the original hardware. So there is over a hundred years of corrosion and since these contacts are out of sight little attention is given to them.
This can easily be checked with an ohm meter, ideally there should be zero resistance. Testing can be do without pulling the box apart but to repair this the bottom panel with the contacts must be removed. It also a great time to clean the switch. The contacts were media blasted and lubricated with conductive grease. I also made the lettering in the switch white again.
The brass latches were disassembled, cleaned and polished. The wood was stripped, lid repaired, stained and sealed. I also nickel plated the box mounts since they were rusty.
With rebuild coils and box the owner will again enjoy a much better running T.
During the spring replacement I noticed a lot of corrosion around split rivets that hold the springs (see photo) and wire that carries power to the coils. Measuring the resistance on each spring contact revealed one contact had very high resistance, it was measuring 68k ohms. This would essentially stop the coil from working since very little current would get into the primary coil. The other contracts measured 1-3 ohms, this resistance will have a negative effect on coil performance.
So although this coil box would have four rebuilt coils they all would perform poorly due to the resistance inline with the primary coils. I believe this is a bigger issue than owners realize. Most coil boxes are still running with the original hardware. So there is over a hundred years of corrosion and since these contacts are out of sight little attention is given to them.
This can easily be checked with an ohm meter, ideally there should be zero resistance. Testing can be do without pulling the box apart but to repair this the bottom panel with the contacts must be removed. It also a great time to clean the switch. The contacts were media blasted and lubricated with conductive grease. I also made the lettering in the switch white again.
The brass latches were disassembled, cleaned and polished. The wood was stripped, lid repaired, stained and sealed. I also nickel plated the box mounts since they were rusty.
With rebuild coils and box the owner will again enjoy a much better running T.