Toyota Repair Problems? Ask a Mechanic for Answers ASAP
Hello I will help you with your question,
If you want enough power to run a heater you will need to install a dedicated circuit straight off the battery. A fuse at the battery and 12 gauge wiring properly protected to the rear will give you 20 reliable amps to use. I don't know ifthat would run a heaer but it will drain a battery fairly fast.
Please let me know what you are thinking of so I can help