Any ideas on what could be causing the speedometer and gas gauge to work intermittently , no lights on the shifter or heat/air panel, and the radio has power but will only stay on for a few seconds before loosing sound. The cigarette lighter wasn’t working but I replaced the fuse and that worked. I’m stumped.

 

when the radio loses sound, does it's light stay on or does the unit go dark? My sense is its time to check into a wiring diagram to see what comes off the ignition switch, what relays are in common, what ground points are in common and whether the circuits go through the CEM. I'd try a few things - wiggle the key when they go out to see if that brings the lights back on, remove/clean reinstall the connectors going to the CEM (if this is a Gen 1 S40, the CEM is right above the hood release and has 3 big connectors to it.

 

It never looses power. The sound just goes away. I have a feeling the radio, speedometer, fuel gauge, and panel lights all failing are connected in some way. Everything keeps pointing to the CEM which I took out and cleaned all of the connections then replaced but no luck.

 

sound systems typically have 3 components - the head unit, antenna amp/connector to the antenna and the power amp to the speakers. If you get no radio but sound on tapes/CDs it usually points to the antenna amp/connector. If you get no sound on any input then its either in the head unit or the power amp (not all models have an external power amp). Since you suggested you lose sound after a few minutes, that suggests to me some component is heating up and the expansion is creating an open circuit. SInce you say the lights are staying on it sounds like its internal and not the power source. (although the backlight may have a separate source you so need to see if the radio power light is on). Is this a Gen 1 car? If so, you can swap in a replacement CEM no programming required. Typically a used CEM can be had for $50-75 on eBay or via a recycle yard. In the mean time you can check fuses/relay output volts etc.