Hi, I have a 2010 F150 Lariat 4x4 with the 5.4. It has around 63,000 miles on it. I purchased this truck last winter and recently have noticed a pretty heavy vibration when the AC is running. It only vibrates when I am at a stop. If I apply a little throttle the vibration seems to go away or it goes away if I shift to neutral. The vibration is not violent but it is above average and I would definitely not consider it normal AC vibration. Any help would be appreciated.

 

Need more input. Does the vibration go away when the a/c is turned off? Has any part in the system been serviced or replaced?

 

Thank you for replying. Yes, the vibration goes away when the AC is turned off or when the compressor kicks off. I have only had the truck for a few months so I am not sure on the AC maintenance records. The freon seems to be full.

 

It could be a bad belt tensioner or slipping belt. Otherwise, I think you're gonna need to get the a/c professionally inspected. I never mess around with them...Too important in the south!

 

Thank you again for your reply! I will check into it.

 

Are you sure you aren't just feeling a drop in the rpms from the air compressor putting a load on the motor? Sometimes the rpms dropping a little low can be described as a rough idle. I think my truck at idle is a little rough because I think the rpms are set low. New spark plugs can sometimes fix your issue.

 

https://www.ford-trucks.com/forums/1...d-in-gear.html

I had a very similar issue...never solved it, traded truck simply due to high mileage...

 

Olytlr - Thank you for responding. I am absolutely sure it is not a normal AC vibration. It is a little more aggressive than what I have experienced with other vehicles. It is not violent nor does it feel like the truck is about to stall but it is a good strong shake. If I pop the hood I can see the belt tensioner pulley shake back and forth. I replaced the tensioner pulley a month ago do to the bearings being shot. Maybe I should replace the arm that holds the pulley along with the plugs?

travlnman - Thank you for the link!

 

Maybe I should replace the arm that holds the pulley along with the plugs?
Yes, I think the problem would be in the tensioner body itself. The springs can break or just let the belt go slack and bounce around.

 

Thank you again Thunder:Raven. I will order one and put it on and let you know how it goes.

 

An experiment to try , which I did with confusing results. Two people are preferred here. Get it warm by driving a few miles. Park with vehicle running, turn air on, parking brake on, put in D with second person holding foot on brake and see if you get the rough idle/vibration. Then, unplug your connector for the brake lights, and repeat. Mine would not be rough with connector off. I have the Torque App on my phone , and it shows a significant drop in RPM , down to nearly 500, and I felt that with the AC on, it was too much load at this RPM causing rough idle. If I had kept, I would have probably replaced the throttle body...they are a couple hundred bucks on Rock Auto. I replaced belt, pulleys, plugs, etc, etc...with no change.

 

Another thought, perhaps the clutch is comming in and out causing the tensioner to dance around. High pressure switch, low pressure switch if bad could cause the clutch to come in and out rapidly (though unlikely). Also more simply check the clutch connector at the compressor and make sure terminals are good and it snaps solidly into place.

 

Did you get it fixed?

 

Sorry I just saw your post Thunder. The belt tensioner came in but I have not had a chance to put it on. Maybe I will have time this week. I will update you with the results.

 

Bumping to know the results with new belt tensioner on. Also if you can test the voltage at the compressor port to know if it is in the operating voltage when vibration happens.