The light should turn green. Had tbis same experience with my showdown charger. If they cant get the charger right what about rhe unit? Vex man all the way now
if you had read what was said, you would have read it is green.
if you plug your charger into the wall and not onto the battery it will be green.
this means an open circuit while plugged in. if it is green while not plugged in at the wall and while attached to the battery then it is a faulty charger that lasted two years.
an open circuit can include loose battery terminals or loose fitting quick connectors at the charger plug or a bad battery among other things.
so if you had this same open circuit experience with your showdown, then the fuse would be the main culprit. a fuse can blow or just get defective over time. if it blows it can because it had too much load while hooking up the charger. this can happen if you plug in the charger at the wall first and then plug the battery onto the other end last. this creates a surge of energy the fuse thinks it needs to protect the circuit and opens up. give the charger some thing to do before plugging it in is best to avoid blowing fuses. so if hooking up the wrong way doesn't blow your fuse all at one time it can hurt it a little each time your doing it until it is open, but you can't see that it's opened. as said a tester is all that is needed and those are cheap enough at 6$ harbor freight.
showdown had the fuse blow when hooked up wrong more than any other sonar i have read about for people not knowing how to hook them up. the fix is super simple for those who didn't know how to use the charger and that is to bump up the fuse rating by one amp. the stock 2 amp is a little small for the application unless connected correctly.
as far as these types of chargers are concerned i don't trust our lives to them because i have had a wire fire while at home from this type of charger, but a different brand. this is also why many of us in the know use some thing else such as what i recommend and that is the battery tender jr. even for your vex. they are 25$.
if you trust yours, you should do it on cement or some thing that can't catch fire and ideally not in your living space so you can't breath the smoke from the fire and so you don't have smoke damage.
you ask about the marcum unit. nothing is wrong with mine. the op isn't complaining about his head unit. sounds like yours was fine also and the charger has been working for a couple of years and still maybe working for the op.