I had the opportunity to use my FasTrak yesterday on the Express Lanes on the way home. I was still waiting on my license plate and since traffic was kinda heavy I took the chance. I left my FasTrak device in my center console. Every time I went through one of those sensors, it triggered by beeping twice.
This was using my FasTrak Flex and not the newer candy bar size. It wasn't buried in the center console and was sitting on top of everything so YMMV.
As current Tesla owners know, FasTrak is very picky about where it should be mounted on Teslas in order to sense the device. I believe they still do require you to mount the device so you're still taking a chance if you're not mounting it on the windshield.
This was using my FasTrak Flex and not the newer candy bar size. It wasn't buried in the center console and was sitting on top of everything so YMMV.
As current Tesla owners know, FasTrak is very picky about where it should be mounted on Teslas in order to sense the device. I believe they still do require you to mount the device so you're still taking a chance if you're not mounting it on the windshield.