Toyota Repair: 1999 Chevy Prizm Electrical Problem, 1999 chevy prizm, chevy prizm

Question
I have a 1999 Chevy Prizm (which is really a Toyota Corolla), which is having significant electrical problems, with no apparent cause.

The problem started with the headlights and auxillary radiator fan running even with the car turned off with no key in the ignition.  Additionally, we are unable to start the car any longer.  We have ordered the factory service manuals to assist in the repair, and found that if we disconnected the DLR module which is located above the glove compartment, the lights and fan will no turn off, and the car will start.  However, with the car running there are no lights, and if I turn on the left/right blinker, in addition to the signal on the dash panel blinking, the brake light blinks and the ABS light blinks.  Furthermore, if I turn on the AC, the car immediately dies, and if I turn on the 4 way flashers the car immediately dies.  Assuming the problem was with the module, we pulled it out and could identify several of the electrical components that appeared to be burned.  We purchased a new one and installed it, but it did not solve the problem.

At this point I took the car to the local Chevy place (1/2 hour away) and after 1.5 hours, the best option they could come up with was that the multi-function switch in the steering column was bad (a $400 switch).  The service manager I have known for several years, and he recognizes I can't afford to sink $400 into this switch.  He recommended that we find a steering column at a junk yard that we could pull the switch out of.  We found it easier to simply replace the entire steering column ($75.00), since it's only 4 bolts and the plugs.  Unfortunately, this did not solve the problem.  At this point, we are pretty much stuck.  The best the dealer can suggest is that it is in the wiring harness someplace, but I can't afford to pay them to hunt for it.  I'm hoping someone has seen this problem before and might be able to direct me more quickly to what the solution might be.

Thanks!  

Answer
Yes I have seen this problem a few times, the dealer is correct, the problem is in the wiring but it can be repaired in most cases, the problem is under the dash on the left side, there is an electrical connector that has a lot of ground wires going into it, the connector may be taped to the wire harness, the problem is that the ground connections get corroded and build up resistance which causes the wires to overheat causing all kinds of strange problems. The solution is to cut out the burned wires and solder in new wires and clean the connections. Have the dealer look for this connector, it has a bunch of white/black wires going into it and coming back out, the connector is plugged into a socket, all it is is a ground bus connector, fixing it will solve the problem, because of this the DRL light relay may also need to be replaced because in most cases it shorts out when this happens.