Turn A/C On - Low Vacuum and Low Idle/Stalling

[98GSX-WI]

I searched but couldn't find this exact problem and I am hoping that someone will know right away what might be wrong.

When I turn on the A/C my vacuum drops and my also idle drops dramatically and the car sometimes stalls when not moving. (The coolant temperature also rises quite a bit, but not sure if this is related or not).

Is there some valve or solenoid that needs replacing -- or something in the A/C system that would impact the vacuum?

I also noticed that my battery voltage seems to drop to about 12.5 volts (monitored by Apexi Turbo Timer) when I turn on a lot of things like the A/C. So I'm thinking that maybe it could be the alternator or something electrical?

Any suggestions are welcomed. Thanks!

 

[Gstclipse69]

I would check/replace your isc. It helps maintain a steady idle when you cut things on like the ac.
DmTaLoN's Idle Speed Control Test/Fix Page!

 

[98GSX-WI]

Thanks for the reply. I have ordered an ISC. I suspect that you are correct and this is the part that isn't working right. I will update this thread after it is installed to let everyone know if that was what was wrong.