Low Voltage Problem

I have a 90 s10 blazer 2wd 4.3L(285 km on it) with a weird electrical problem. The voltage gauge at idle is at the red line 9, while driving it will be at 12 to 13 and will not go any higher. When I come to a stop the lights will dim, the fan will slow and if its cold out it may stall. I've checked the battery and tried a different one, same problem. I replaced the alternator and put on new belt. The battery reads 12.6v and alternator reads 14.3 volts. A while back my DLR would not come on and 6 months later one of the headlights burnt out, I replaced it and cleaned the connections, DLR now work but every time I started the truck or turned on the lights I heard a buzzing from under the dash. That lasted for about 2 weeks and hasn't returned. I have cleaned all the grounds that I could find, replaced cable from alt. to batt., checked all fuses and they are good. Has anyone had this problem or suggest anything I have missed. Please help i'm pulling my hair out on this one.

Sounds like the battery is shot.

I have a 90 s10 blazer 2wd 4.3L(285 km on it) with a weird electrical problem. The voltage gauge at idle is at the red line 9, while driving it will be at 12 to 13 and will not go any higher. When I come to a stop the lights will dim, the fan will slow and if its cold out it may stall. I've checked the battery and tried a different one, same problem. I replaced the alternator and put on new belt. The battery reads 12.6v and alternator reads 14.3 volts. A while back my DLR would not come on and 6 months later one of the headlights burnt out, I replaced it and cleaned the connections, DLR now work but every time I started the truck or turned on the lights I heard a buzzing from under the dash. That lasted for about 2 weeks and hasn't returned. I have cleaned all the grounds that I could find, replaced cable from alt. to batt., checked all fuses and they are good. Has anyone had this problem or suggest anything I have missed. Please help i'm pulling my hair out on this one.

hmmm ... new battery and alternator and still big draw that low rpm gen can't match ... all i can think of is something drawing way more current then it should or has short in it ... but i'd expect that to blow fuse ... i'd still try pulling 1 fuse at a time to see if voltmeter jumps, telling you atleast the problem circuit, maybe. check that no wires disconnected or bare anywhere under hood or dash or behind radio if you moved that.

oops, in rereading your post i think you may have already answered area of drain or short or bad ground or excessively high draw ... headlight that burnt ... check it's ground wire ... i dunno what dlr is but that acted up so another suspect ;-)

i dunno what dlr is but that acted up so another suspect
Thanks Cam59, DayLight Running lights(DLR) i kinda suspected it could be from the lights but haven't found any bare wires yet. I'll try the fuse elimination and post back on what I find. Thanks again..

A new twist to this problem but it seems to be fixed. Last week my distributor went, so i had it replaced. The blazer then was running like crap with surging and stalling after that. The mechanic said my IAC motor was failing, I replaced that and my gauge now sits at around 13 volts and doesn't move. I can't recall it ever being at or above 14v, its always been around 13 so i'm happy. I'm guessing my idle was to low or the IAC motor was drawing to much power to just to keep the engine running at idle. Thanks for all your help.