it seems to be discharging with the air on, when I turn the a/c off its ok.

 

Are you saying that the charging system is discharging when the AC is on and it drops your idle?

Your idle speed might be too low and it is below the threshold of charging.

Your engine when it is idling correctly should barely have any drop in idle speed when the A/C clutch is engaged, we probably have more torque at an idle than most 4-cylinder cars have peak, they shouldn’t act like a Pinto when you switch on the A/C.

Try and bring up your idle speed a bit.

An easy way to adjust your idle speed without fighting the locknut on the pump is to simply slip a short section of 3/16” rubber hose over the end of the screw that adjust the idle stop now you can simply adjust the idle with a screwdriver by pushing the tubing back of fourth on the end of the screw, mine has had this for years.

If you look to the left of the AFC housing you can see the tip of the orange hose.



Or you could have an overcharges air conditioner.

Jim