Landlord Has Taken Over A Week To Fix My Heater, What Are My Options At This Point?

I live in Northern California in an older duplex. There are honestly quite a few problems but it has its charms and there’s nothing that’s been detrimental to my health or anything so I mostly ignore the issues. They were all noted to the landlord obviously since I didn’t want to be charged for things that weren’t my fault but she never has jumped to fix any of it. Recently my heater has been acting up and takes a while to start (it’s an older model that I honestly can’t even place how old it is) so I mentioned it but again she did not do anything. Last week on Sunday it completely stopped working. I had to pester her all day through email and phone call to get any sort of idea as to when a repairman would be out to fix the heater. She had no idea but then last minute said the next day. He showed up, left after about 5 minutes saying he needed another part and this song and dance played all last week which concluded on Thursday to him saying we need to rip the whole unit out. I asked when this would be fixed and no one is giving me a direct answer. She said it would be fixed on Friday but no one came by and she stopped responding to my messages. It’s about 25 degrees F here at night and it’s impossible to warm it up during the day since it’s cold all the time. I’m getting really fed up with freezing and just want to know what my options at this point are.