I just had the 90k service done, and since then the Highlander has no heat. I've mentioned it to my mechanic who is going to see if there is a procedure to bleed the system of any air pockets, etc. I wondered if there is an issue with the 4 cyl. on an '03 Highlander with this problem. I saw a post talking about the heater controller, but my heat worked fine until this service so I don't think that's my problem...

I'm beginning to think that the problem could be the heat controller - last night the heat worked like a champ, but this morning I get no heat again. It could have not been noticed since we haven't needed to use the heat until now... Time to practice the soldering skills.