Hi
I have a trane xb80 furnace that was blowing cold air and as I read in this forum and according to the led code with flashing 4 times I found that I should change my swith limit , so I took out the switch it was l190f30 but the shop gave me l180f40 and told me it should work . I installed it on the furnace but it was blowing again colx air and whenever I was trying to put the temp above 23 it was stoping blowing air . And after a while it completely stop working . Now it's not working at alland it seams ghat there is no power in the furnace and the light is completely off . Please help we what to do ?

Flash codes don't mean the switch is bad. It was probably just doing it's job. If the limit switch was opening then the furnace was over heating. Make sure you have a clean filter.