2001 lincoln continental: left rear suspension is sagging, pumps up when started and starts decreasing when engine is shut off, also all turn and brake light do not opperate all at the same time.

Sounds like the left rear airbag or the air bag solenoid is bad.

Do not see how that would affect tail (turn and brakes) lights also, thinking something electrical, but I checked fuses and relays.

Electrical problem is very likely not related to the suspension problem as you have already figured out.

You can find the replacement air bags on ebay for $70 - $100. If you're even the least bit mechanically minded, this is a rather simple fix. Or you can replace the air bags with springs. Also can be found on ebay or at a local junk yard. I've also seen a replacement spring kit at full retail for about $400.

You can always replace them with a set of spring shocks for the price of 1 air shock and then remove the fuse to the compressor after installing.