Just as a follow up to this. I'm not sure if they changed their manufacturing process since this was posted but they seem to be using circuit breakers in these now. I ordered a Dorman 904-304 from Amazon last month and didn't replace my glow plugs before installing it (all 5 fusible links in old module blown) and it simply threw a code for all 5 glow plugs when I hooked up my MBII scanner. I disconnected the Dorman module again, checked all glow plugs with a meter, all 5 were bad. I put new glow plugs in, hooked the Dorman module back up, and it worked fine. If this thing had fusible links they would have blown again and I would have had to send it back for a new one. So I assume since it works fine, it must have circuit breakers.