85 Charging Problems W/AC on!

Hi guys, When I'm driving with the a/c on and I stop at a light, my voltage drops so low after about 15 seconds it red lines and I have to rev the
engine or it will stall on me. Whats your thoughts? Also what's the norm for oil pressure? Mine is at 80 all the time. THANKS, Tim
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sounds like you may have a voltage regulator problem, it is common with the C4's i think they upgraded the alternator in 86 or 87 so if you do have to change out the whole alternator i would get the newer one.
80 psi o the oil pressure all the time is not right at all, i would start with a new sender from GM or you can take it to a shop that you trust and have them hook a gauge tester up to it, most shops that do much electrical work will have one of these little units, you might try unplugging the wire from the oil pressure sender and see if your gauge goes to 0 psi. i believe that (from memory) that most GM's go from about 1 ohm at 0psi to 80 ohms at full gauge deflection, i am not sure about the digital dash like yours has, but that is the way most of the GM stuff in the 80's worked.
as far as what is normal, that depends on a lot of factors, bearing clearances, temps, (above 180) oil viscosity, rpm's. But a general rule of thumb is ten psi/thousand rpm with a fully warmed engine MINAMIM.
on my 87 at about 1500 rpm i see about 37 psi motor hot and running Mobil one 0w40. Greg On Mon, 1 Aug 2005 18:16:58 -0400, "Tim & Cindy McDonald"

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Get your voltage/charging problem solved before you work on your oil pressure reading.
Bones '87 & '95
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On my 85 when idling I am around 55 psi for oil pressure and its up to around 70 when toying around. I use mobil one 15 / 50.
On your problem... are you sure that the compressor is not seizing up and dragging down the rpms? Does the serpentine belt squeal? If you were suddenly not charging the battery should keep you running.
I have 129k on engine although not sure if it ever been apart. In general does a 350 push oil at this milage? Passed emissions fine here in Mass at around 20 to 50 percent of allowed emissions. I assume that past owners were not babying it as its red and 4 plus 3.

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