yes, red=12V ... there are body length differences, one is longer, but I'm not sure which ... and there will be internal differences a qualified auto electric shop could ID, field winding [the ones attached to the case] resistance is less on 6V than 12V

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics