Six volt radios can be damaged if operated with
an eight volt or twelve volt battery
The dropping resistors used in the 50's and 60's to allow 12 volt operation for 6 volt radios were a patch, at best. It subjects the radio to voltage swings that are hard for it to tolerate. It also adds about 40 watts of heat under your dash.
An eight volt battery will make your 6 volt starter turn faster but it will also shorten the life of your radio and headlights and the rest of your car’s bulbs. Six volt cars all started when they were new. If your engine does not start with six volts it probably needs a tune-up or rebuild, not an eight volt battery.
Car manufacturer’s went to 12 volt systems because the accessories were becoming too much of a burden for the 6 volt electrical system. When cars first came about, radios and heaters were options, not standard. In the fifties, air conditioning was introduced. Rear window defrosters would soon follow. To handle all these accessories with a 6 volt system would require impractically large cables. It was more cost effective to double the voltage of the generator, thereby doubling its power and also reducing the wiring sizes. It also allowed greater capacity starter motors for the larger displacement and compression ratio engines that were on the way.
Sorry, but I do not guarantee nor knowingly repair radios operated with improper voltages or polarity. However, 6V radios can be converted to 12V. It requires major modifications but, once done, you will obtain the proper operation and longevity from your radio that it had previously.
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