Auto theft system for 1997 eldorado cadillac bypassed but now instrument cluster and ac not working

If this is the analog intrument cluster and the entire instrument cluster is intermittently losing illumination, remove the instrument cluster light fuse and replace it with a new fuse. It is remotely possible that the actual fuse holder wires have broken due to age and would need to be soldered back together.
If this is the digital instrument cluster and the entire display is going dead, it could be anything from the wiring harness to the BCM. If it is the digital instrument cluster, I can really only recommend taking it to a reputable shop or Cadillac dealer to service.

Check negative connection to car frame or loose battery connections.

You probably can't.
If the anti-theft module is in the cluster, you would need the correct key chip for the car the cluster came out of.
You might be able to bypass the passkey system by running a wire to the fuel pump relay and other components.
You may need a shop manual to find the circuits.

You will need to call a locksmith on this.

if the theft light is was flashing on you, put the key in the ignition and turn all the way until the instrument cluster lights up, just don't start the car. leave it like that for aprox. 10 min. or until light goes out. when that happens, turn of(don't take out keys) and try to start car. hope it works.

generally when half the cluster fails it points a a failed instrument cluster, Not the ECU. Either way I would have it diagnosed properly before you replace anything.

Unfortunately i can't really give you advise on how to bypass it since in this case the info can be used for auto theft. If you need help installing the ignition key switch i can be glad to help.

remove ac vents with flat head screwdriver . thair should be a 7mm bolt in each vent holding tha dash pad on remove them. remove the trim going to head liner from the dash pad. use a 7mm to remove the bolts holding the cluser in place should be one each side and 3 across the back . disconnect the wiring harness and your done. also disconnect the negative batery cable when doing this

dealer scan tool is required to reprogram your Passkey III system into the panel control module witch is part of the instrument clust.

U ARE GOING TO HAVE TO PULL THE INSTRUMENT CLUSTER OUT AND SEND THE ENTIRE UNIT IN FOR REPAIR AT AN AUTHORIZED GM DIDGITAL DASH REPAIR CENTER, YOUR DEALER CAN SUPPLY THRE NAME AND PHOMNE NUMBER, THIS IS NOT A FUSE PROBLEM.