OK. for starters 2001 XJ8 British Racing Green
one of the dash board lights left pod was out, if i tapped on the dash right above it it would go on and off. so i decided to take it out and replace all the bulbs at the same time. put it back together and none of the backlighting works now. when i hooked up the battery all the lights and warning lights were flashing in random order, battery not charging, check engine,low coolant, door open boot open etc. unhooked battery again, and checked all connections. pulled all the bulbs out and put the old ones in, now everything works fine except the backlighting in both of the pods and the backlighting in the trip computer pod on the right of the steering wheel. please help, what did i do wrong.

 

I have replaced various non-working bulbs in the dash a few times. It seems to me that the contacts tend to oxidize over time which leads to poor electrical contact with the bulb. The last time I had the instrument cluster out I cleaned all the contacts thoroughly, tweaked the wire contacts on the bulbs, and used a small amount of dielectric grease on each bulb/contact. Have not had any problems since.

 

pulled the dash panel out again and checked all connections, everything works as stated, except no back lighting on the speedo and tach. is there a fuse for these such lights?

 

This happens to me a lot. Especially with the older newer cars (post 1995) with multiple very fine pin connectors. The problem is usually the connector that connects to the back of the instrument pod. The very fine pins sometimes barely make or break contact. You have to make sure everytime you unplug or plug that connector back in, you pull it out or push it in straight and carefully. Any pins that get slightly bent will cause problems. It is not a corrosion problem. You may have to plug and unplug several times and check all the lights. Do not install the instrument pod back until all the lights work, then gingerly push it back in, otherwise you will not get a light to work again.

The other issue is the lamp base not making very good contact with the printed circuit board. Tighten the connector at the base and hopefully it will make better contact with the PCB. Check your replacement bulbs by jury rigging to a 12V battery first.

If all else fails, whack the dash hard with your fist a few times and it usually works! It worked to get my dash lights to work on my Mercedes and got my original AM radio going on my '56 Olds!