instrument cluster and taillight issue

[slimcat7m3]

Hello,I am having a wiring issue with my 89 240. I recently installed a boost controller in my car and initially installed it wrong. I am a capable mechanic just wired it wrong. Now that is fixed but around the same time my battery/alternator light came on. I checked the charging voltage and it was low so I had it rebuilt. When I installed it the alternator seems to be charging but the light never went out. I am sure my other problem is related so when I turn my headlights on I blow the taillight fuse and my instrument cluster lights and taillights don't work, headlights and idiot lights still work. I have my whole dash and left side of the car torn apart, and cannot find any thing. Its probably a ground wire somewhere but could some one give me an idea of where to look. I have been looking for days. Keep in mind I had no issues before I installed the boost controller. Any help would be great. Thanks

[amolao]

On the first problem I will tell you to back trace your steps to the beginning of the installation and while looking at the FSM wiring diagram look for any burn wires, miswired cables,etc....on the cluster problem, disconnect the cluster and see if the fuse still blows....you can still have headlights with the cluster out...is a safety thing. But if it works with the cluster disconnected then you have a short in the cluster.