I’ve had an electrical problem for over a year now. It began with the SRS light staying on and “sapping” power (I know now that isn’t what was happening, but that is the way that it appeared) from the rest of the electrical system (see my "Penntellect" 1/13/2005 posting.) Now, it appears that the warning lights that are coming on are not “false alarms” but rather real problems related to the electrical system. For example, the Overdrive Indicator light comes on without my input, I can’t turn it off manually, and I can’t drive over 45MPH at 4000RPM. I’ve taken my ’93 940 to the dealership with this electrical issue, but they don’t want to do very much because they won’t guarantee they can fix it. I have run and cleared diagnostics on it more times than I care to say, but diagnostics really isn’t telling me anything (for instance, the ABS diagnostics tells me it is a crash sensor/dealer fix.)

The biggest piece of new information on this problem that I have (though I don’t know how to interpret it) is related to the key switch / ignition switch replacement. The dealer told me the last time that I took the car in to them that when they have seen this symptom before, they have replaced the key switch and that has been the remedy but they would not guarantee that would fix my problems. I have attempted to replace this starter switch with both a Scan-Tech replacement and an OEM replacement, and both of them seem to be shorting out (or triggering a shutdown switch?) the electrical system after I reconnect the battery and turn the key to Position iii-whatever it is, the car loses all electrical power once the key is turned.) After about five minutes of sitting there contemplating where I went wrong, the power mysteriously comes back on-but I can never crank the engine. When the old key switch is reinstalled, it starts just fine but I’m back to the same old problems.

Does anyone have any ideas of what I can check or what might be causing this? I’m thinking that some feature preventing this short/trigger on the old key switch must be burnt which isn’t on the new ones. I have replaced the Overvoltage relay (the fused relay which regulates voltage coming into the dash), but am beginning to think that this problem is in the ECU. Would any of you agree and think it worth investment in a new ECU?

I appreciate and look forward to your feedback!
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1993 Volvo 940