88 deville, dash lights flickered , then dimmed and went out complely. climate control no longer works no gas guage, no a/c or heat and no speedometer.all fuses good, if i take out the relay and push it back in to just barely touch the contacts, the digitals light up for just a second.i have replaced the bcm, the climate control, and speedo cluster.i have cleaned both battery connections but still nothing . i have wiggled all harnesses and connections could someone pleaseeeeeeeeee tell me what i am overlooking. i am tired of guessing how much gas is in the car and and sweating down here in florida. my back is shot and the wife is miserable ( its her car ) please help me. thank you .

Disconnect the negative battery terminal.
Then go back to the relay you mentioned and, with a small screwdriver, bend those contact inward so they'll make better contact when you put the relay back. Then test it to see if it lights up again. Test the relay if this doesn't work; it may be defective. Sometimes, if one of the wires on the + terminal is even slightly corroded or not installed "just right", this can cause the same problem. Good luck!