Why does my f150 shake when air is on?

I have a 2005 f150, when my AC is on (it’s summer in the south so yes it’s on constantly) my truck shakes. The best way to describe it: you know when you’re at an idle, and the vehicle wants to stall out and it has that shake to it? That’s what my truck does when the AC is on, I mostly feel it when there is no gas applied.
Also my AC makes a horrid sound when idling (like a loud pop now and then) and unless I’m driving, it won’t blow cool air.
Why?! Simple fix or time for a new AC?

It won’t blow cool air unless you are driving??? Does that mean the moment that you stop the cool air also stops? Or does that mean that when you stop the temperature out the vents slowly creeps up… And then, after the vent temperature has become somewhat warm, you hear the “horrid sound?”

If your problem is the latter situation the radiator fan is likely not functioning and continuing to operate the AC when idling could seriously damage your system.


What engine?

It is possible that you have a defective IAC idle air control valve

Question . . . is the idle fine if the AC is off?

As for the noise, it could be the compressor cycling on and off

It could also be that the compressor is about to explode (internally)

Another question . . . when the AC is on at idle, is the engine idling at a slower than normal speed?


it’s a 5.4 the idle is fine with AC off and my engine idles fine with AC on or off


When I’m driving then stop, the air slowly warms up until I start driving again. I was told this is normal with my truck but there isn’t a wide enough space for air too enter the system, but I just don’t think that’s right.

Then the “horrid sound” I hear will happen when driving also. It’s a loud pop sound. But I mostly notice when idling, and I know it’s something with my AC because it was fine this winter when not in use and made that sound last summer also when I used my AC.

Has the AC been recharged in the past? By someone other than an AC specialist?
It might be low on refrigerant oil. Or as @db4690 says the compressor is in its death throes.

The AC compressor kicks on and off via a “clutch”. It sounds like the compressor might be bad causing a lot of extra drag that causes the noise when the clutch kicks the compressor on. I think you need to go to an AC shop, or your trusted mechanic to have the compressor checked out. Have you noticed a drop off in either performance or mpg? This would be likely if the compressor is taking extra power from the motor.

My fiancé added some AC stuff (yeah i know technical terms there) last summer BUT it was acting oddly then and has simply gotten worse this summer with the whole making my truck shake thing.

As a matter of fact, I do believe the mpg has dropped. a drive I make twice a week seems to be taking more gas than it did in the past, which I noticed a week or two ago.

by the way, thanks y’all for all your ideas/advice! I appreciate it

You might get the truck scanned for codes. The chain type auto parts houses will do this for you free. You might also note if the idle speed drops a little when the compressor kicks on. If it does that could point to an Idle Air valve problem as mentioned or possibly a vacuum leak.
However, an Idle Air valve problem does not always set a code.

Without hearing the noise, I could theorize that it might be a control door inside the dashboard banging open or closed as some of those are vacuum operated; even ones with EATC heater/AC controls. A blend door actuator on the way out might cause a noise also.

Bless your heart. There’s no reason to be rude. I’m looking for opinions as to why my AC is doing this, not arrogant comments.

Thank you I didn’t even think to have them scan for a code, sometimes the simplest things are easiest to forget I guess.
I really appreciate y’all giving my some great advice. Thank you


From reading your replies, it sounds like your AC compressor isn’t doing its job and is about to let go.

Lovely. I suppose on the bright side, if and when it goes out, my windows still roll down until I can afford to replace it! Lol


Let me give you advice from a professional mechanic

Get that truck to a shop now and have it diagnosed

If a shop tells you the compressor is about to let go, replace it NOW


At that point, debris will have shot into the discharge hose, condenser, and possibly the suction hose.

At that point, this is the bare minimum you’ll need

AC accumulator (you always do on major repairs)
Orifice tube
Flush the hoses
Install an inline filter to prevent any remaining debris from ruining the new compressor
Might need a condenser (flushing is not always effective)

Sometimes when a compressor lets go, it throws the serpentine belt.

I’ve seen cars overheat when the belt gets thrown and the driver decides to keep going

So . . . spend a little now or a lot later

I agree with @db4690 about getting the truck checked out at least. If you can’t afford the repairs at the moment and continuing the operation of the AC system will add more damage then you can stop using it at least. It would be helpful to know where the poping noise is coming from.

There may be some minor engine problems that is causing the low idle to happen and the gas mileage to drop down. There are lots of possibilies that could cause that kind of trouble. A good shop should be able to pin down the problem if there is one and hopefully not cost you a lot to fix it.

You’ve gotten a list of comments here which, to those not knowledgable in mechanicas, might seem like disconnected guesses, but if you’l allow me to elaborate I think you’ll agree that they’re not.

When you engage the AC, a clutch engages a compressor that places added load on the crankshaft. The Idle Air Controller (IAC system adjusts the idle upward a bit to compensate at idle.

In your case, it sounds like either the IAC isn’t corrected for the added load of the compressor, the engine isn’t operating at optimum and is unable to smoothly carry the added load, or the compressor itself is binding and placing too much load on the crankshaft. The AC noises suggest to me that the last of the guesses may be the right one.

Conditions that cause less than optimal engine operation, and IAC problems, will show up in the engine’s computer as “fault codes”. Having the codes read is an excellent first step, because correcting any faults may just solve the problem.

And some are suggesting getting to to a shop ASAP because if the compressor is failing and binding up, it can cause other damage if it does so. If the compressor binds and the belt pops, it can fly free and cause physical damage. If it alsodrives the alternator, itll also leave you broken down on the side of the road.

I hope this helps. Everyone here is trying to help, and it can get confusing.