2001 S10 Blazer: With ignition in off position,Speedo sits maxed out @ 100mph, fuel gauge will point straight down at 6:00 position, will not start. If I "smack" the dash above steering wheel,fuel gauge goes back to "normal" position. Speedo still stuck at 100, engine will not start,and it sounds like when you have a bad connection from battery. Don't know if I have a bad ground somewhere between battery and starter,not sure where to check. This Blazer has always had intermittent electrical issues with the ABS and brake warning lights coming on/going off for no reason. When I first had trouble with it not starting, the gauges did not go crazy,and the engine turned over but would not fire.I disconnected the battery cables to look for corrosion, and when I reconnected and them, the electrical issue with gauges came back. The fuel pump is coming on. The battery is only a few months old. Could I have a bad ignition switch and/or a bad connection after battery? Please let me know how to get to the ignition switch and also where I should check for bad connections after the battery. Please let me know where all the grounds/and or hots connect to frame,etc.. I am a member here, but if someone posts a link such as a schematic, and I try to see it, it says I don't have permission, so any explanation would be much appreciated from the very knowledgeable folks here. Thank you

UPDATE: I found several ground places and cleaned,tightened. Now it seems I have a MAJOR short somewhere. Is it possible for a bad ignition switch to cause the following: Without the key in the ignition, the alarm that sounds for leaving headlights on or key in ignition with door open sounds, I hear something buzzing behind glove box, the temp gauge bounces around, I hear a clicking sound like a relay turning off/on. These all happen pretty constant, but can be intermittent. This is all without a key in the ignition, and needless to say it drains the battery down. I have to disconnect the battery to stop all this. Of course, the engine will not start as well. BTW, I have seen some great tips here on how to get at the ignition switch from Swart and wolfpack, just wonder if I should go there?
Thanks much