Rpms drop when heat or air is turned on

There should only be 1 screw located at the base of the carb facing outward.

The method I use requires a tachometer. If you don't have a tachometer then you can use the "by ear" method, though it's not as accurate.

With the engine off, start by turning the screw all the way in, then back it out 1 and 1/2 turns. This usually give you a baseline to start with.

Start the engine and get it up to operating temperature, make sure the choke is fully open, and have the air cleaner and all vacuum lines installed.

Using the tachometer (or ear) turn the screw (usually out) until the RPMs increase. If they don't increase by turning the screw out, then try turning it in.

Eventually the RPMs will stop climbing while turning the screw (as said earlier, usually out).

THEN turn the screw the opposite direction (usually in) until the RPMs JUST start to drop off. That should be real close to the optimum setting.

This setting is ONLY for the base idle air/fuel mixture and is NOT for anything else.

Hope this helps.

correct rpms should be ~800rpm ac off, and ~1000 rpm ac on.
idle up switch is broken or vacuum hoses attached to idle up switch has leaks.

The throttle body needs to be cleaned, grime in this area prevents the throttle plate from closing completely and allowing air to enter, making the air/fuel mixture lean. Make sure to clean the front and back sides of the throttle body. Also, disconnect the battery during the cleaning process to allow the computer to reset and relearn to the cleaned throttle body.

It's called the tip in procedure. You need to run the engine at 2000-2200 rpms and gently cover the choke opening with your hand. If the rpms go up about 100, it is set right. Too much of a rise in rpms, or rpm surging means it is too lean. No rise in rpms means it is too rich. If you pull a vacuum line and the rpms increase, it is too rich; pulling the vacuum line should keep the rpms steady or cause a slight drop. You need to remove the air horn to access the APT screw. You knock out the aluminum plug and install the air horn again to adjust while running the engine. You can 3/8 tap and plug the hole for easy access or drive the aluminum plug back in when done. Turn the APT screw Clockwise to lean it out and counterclockwise to richen it up. To turn it, make a tool with a 5/16 x3 bolt. Cut a notch in the bottom with a hacksaw or grinder about 1/8" wide. The bolt will fit into the hole with the air horn.

Hello and welcome to FixYa!

If that's the case then the problem will be on the MAF (mass air flow) sensor. If the MAF is faulty the car tends to loose power and erratic idle may occur. One good reason why you are having this issues. I strongly suggest that you have it replaced to resolve the problem.
Hope this helps and thank you for using FixYa! Have a good one!

would change top hose plus make sure there is a thermostat fitted

You need to have your pressues check at lower rpms it sounds like your a/c compressor doesn't have enough of a charge to remove the heat from the air but at higher rpms it can because higher rpms means higher flow and higher pressure.

when it will again on . Check thermostat

You probably have an air lock. Remove a heater hose and get all the air out. Then run it with the rad cap off until it warms up. You should see the water level drop when it finally goes, or if you got the air out with the heater hose, it should be okay.

Since the fan is electrically operated it is not the problem.it seems like more of a waterflow problem:the faster the engine turns-the more the water pump turns.i am only guessing but it seems like it could be low on antifreeze or your water pump is failing..good luck