Originally Posted by 97 SL320

I just looked at the e bay link. He is selling them for $530 , as in Five Hundred Thirty Dollars with 1,643 sold. $ 53 would be pushing the limits for what amounts to a pill bottle, a LED , switch , wire and 3 banana tips. This is about $ 5 in parts to be generous.

The tester is basically a switch that puts a module into test mode and a light so you can count the blinks. There are diagrams and code info on the net so no need to pay $ 530 .