bulb issue

Hello, The gauge cluster bulbs on my 1996 XLT keep going loose. I know for a fact they are not burning out, because I have replaced the bulbs and inspected them afterward, But it seems every time I change all the bulbs and reinstall the gauge cluster, after a little while a bulb goes "out". I...

One of my inspection 'fail' items was no check engine light (key in run position, engine off). Last weekend I took out the cluster, replaced all 6 illumination bulbs and the check engine bulb. I couldn't see any broken filament, so I used a 9V battery & a couple test leads to make sure the bulb...