This can be a sign of a few different problems.
why does my car vibrate when ac is on?
good question! when the compressor of an ac unit is running, there are more vibrations in the engine because it has to work harder. so, this would make your car vibrate. this vibration is usually only felt under hard acceleration or at wide open throttle where sufficient engine power can overcome the added load imposed on the ignition system by being forced to start and stop so quickly with each compressor thrust. if you are having trouble starting it when this happens, have your mechanic check your spark plugs for any signs of damage or dirt/gasses leaking past them.
a great answer! one final thing to be aware of though – lubrication may need to be improved if you're experiencing high levels of vibration which could lead to catastrophic failures
what causes rough idle when ac is on?
the ac is not the only thing that can cause a rough idle. there are many factors that can affect how quickly or slowly an engine will idle.
a cold engine will typically idle slower than normal, could be due to poorer quality fuel, dirty air filter, lack of maintenance, etc. if this happens after your ac is on it's likely an issue with the ac and you should consult a mechanic for more information.
how do you fix a rough idle when ac is on?
the common fix for this is to disconnect the power of the ac unit. this will cause some people who don't know better to freak out, but it's what the workshop manual suggests. the new fangled central air units use more power than earlier systems, and that takes away from reliability of electrical signals on your car (or anything with electronics). when working on old cars like this, it's best to clean any kind of gunk or grease off before you reconnect everything together so there's no future problems. and remember not to touch any live wires while rewiring!
about these answerer questions…
many of these questions ask about why certain behaviors happen among humans. if they are opinion based instead of research
why is my car misfiring when the ac is on?
your car may be telling you that it needs an oil change.
oils are the engine's best friend. they keep moving metal parts from grinding against each other, they lubricate so things can move, and they carry heat away to avoid under-heating (and possible destroying) your engine. the oil acts like a film between moving parts, too thick to allow metal pieces to scrape against one another by brute force but thin enough for them also to slide past each other without seizing up. and because many oils break down over time, if the oil becomes contaminated with water (from rain or dew), it should be changed immediately– even if you're not driving 50 miles every day like most people do! when water se