Smiths heater as fitted to my 1959 TR3A

    It really helps to have access to a blasting cabinet / compressor. I invested in one a couple of years ago and believe me it gets plenty of use. For these heaters , disassembly is very easy as no special tools are required. The biggest challenge is finding parts if you need something that's missing. For example, the little plastic handles on the doors are not available. One of mine was chipped badly. Luckily, I had a second heater unit that had one perfect handle. So, like many restoration challenges , sometimes it takes two or more units to make one good one. Begin disassembly of the heater by removing the 3 spring clips as shown below. These clips hold the top and bottom end units in place, with the core clamped between them.
    Attachment 59573

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    As shown in photo #8, it was necessary to skim the commutator to restore the surface and improve operation. This operation was not done with a cutting tool. I used medium crocus cloth, which is an iron-oxide coated abrasive cloth, used as a polishing agent.

    This is a good time to examine the motor brushes. These are made of carbon and wear down in normal use. In this motor design it is not possible to inspect the motor brushes by unscrewing a cap on the out of the motor. Unfortunately you must remove the entire motor housing. Visually, a brush that needs replacement will show a dramatically uneven face, with discoloration in one spot, and, more likely, chipping on an edge. It's important to note, however, that it's usually not ideal to remove and reinstall brushes without good reason. However, since most of these heaters were built over 60 years ago, itís a good idea to replace the brushes now. I could not find a direct source of original Smiths motor brushes. I ended up removing one of the brushes and taking it to a motor repair shop. He sold me a couple of brushes for a few dollars. These were slightly oversize in all three dimensions, so I simply filed them down to size.

    After attending to the commutator , the rotor can be inserted back into the motor housing. Now the field winding wires need to be re-soldered to the commutator. This is followed by a test of the motor before you completely re-assemble the heater. I temporally reconnected the fan and connected the motor to a 12-volt DC power supply. You can use your car battery but be sure to put a fuse in series. I recommend a fuse size no larger than 5 amps. With the fan attached and with new brushes the motor was connected to a 12-volt DC supply. I measured just under 2 amps. In actual operation you may measure higher current because the fan will have more load when shrouded by the heater core.

    Reassembly of the heater is simply the reversal of disassembly and is very straight forward. Prior to mounting the heater back in the TR I added an in-line fuse (10 amps) for added safety. Be sure to replace all hoses and hose clamps. There are documented reports of serious burns (to particularly sensitive areas of the human anatomy) that occurred when an old hose burst, or clamp let loose. For added authenticity ribbed heater hoses are available from a few of the major suppliers. In addition you can replace the old faded nameplate of your heater with a new one. I found a supplier of these nameplates on eBay.

    I am often asked if new replacement motors are available for these heaters. The answer is no. So unless you can cannibalize another heater you have problems. However, I have yet to find a motor which was not repairable. Usually a skim of the commutator and new brushes will bring these units back to life.

    If you have any questions, I can be contacted at angelfj@verizon.net

    Best regards,

    Frank Angelini
    Downingtown, PA USA
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