hi, its a 94 s10 blazer 4.3 cpi. when it idles... the volts drop to 12 volts, and the lights dim...the wipers go slow. but when i drive, its fine, and it reads 14 volts. now, if i idle and just tap the gas to get the rpms up to 1000, its fine. ive been a 12 volt technician for 9 yrs and have done everything i know. i tried a new battery, i put a hi-output alternator in, replaced the grounds, all the fusible links coming off the alternator, and still the same. as a matter of fact.... it seems it is getting worse. i hooked up my friends car to it with jumpercables , and still the same. for the 5 years ive had the truck, ive never had a voltage problem and its always been at 14 volts (this is an aftermarket gauge). i ordered an iac sensor from work today, in hopes that it fixes it. does anyone have any ideas? it seems every problem i have with this truck , no one has ever heard of it.