might start by getting the AC system checked out.

you could have high pressure and after being off a while its hard on the ac compressor clutch to startup, over coming the high head pressure, but once it on and running, its ok.

the smell could be your ac compressor clutch burning.

could be a bad fan belt and it needs to be replaced.

big fan belt and I would not want to have to replace it along the highway some where,

do you carry a back-up fan belt in the tool box?

 

I've had the same problem for years. Only does it after the AC has not been run in a few days. Also noticed it won't do it if I wait for the engine to get up to running temp then turn on the AC. No ones knows what it is. I've even had the AC serviced for another issue and the problem couldn't be found during service. Would love to know what's causing it too.

 

Add another one to the list.....Just had my AC serviced about two weeks ago. Blows cold as it every has, but once in a blue moon I'll cut it on and here that same noise..

 

I believe it's probably the AC clutch on it's way out and or compressor.

When the system is running and cycling you have a very high pressure on the return pushing on the compressor.
When It hasn't run for a long time (maximum couple of minutes) the pressure balances between the two sides so a slightly sloppy compressor can make a clank on startup. It doesn't have any resistance right at startup or positive pressure.

Just thinking out loud. I do a lot of AC work and have seen this many times on the same types of compressors.
The plastic smell if not something in the AC clutch has me more confused unless it's fan clutch related.

 

Mine does that right after I start it. Maybe about 3 seconds only does it with ac in on position on start up first start of the day. Was told its nothing to worry about as long as ac is workin


Sent from AutoGuide.com App

 

I have done a lot of thinking on this subject as ive seen many compressors do this. The problem in my opinion is that the clutch is slipping and not friction locking onto the pulley for some reason or another when you first kick it on with a not up to temperature engine. The idea waywardtavel mentioned (not enough pressure upon start up, causing a sloppy clanking noise) is the other thing I support the idea of, the only thing that makes me doubt that is a lot of people have this problem only right after start up and engaging the ac... and not when tuning the a/c on after its been running for a while.. could it possibly be the gap between the clutch and pulley not right? I know they have to be pretty much spot on and set with a feeler guage. also maybe it could just be the material of the clutch wearing out, (idk If they are ceramic or what?) and it takes a bit more of heat before it grabs? just my 2 cents:thumbsup:

 

Have lived with this exact problem for 2 years. AC is still cold and dependable as ever but the noise makes me cringe every time even 2 years later. I find myself enduring the SoCal 105 degree heat rather than turning on my A/c before the engine gets to OT.


Sent from AutoGuide.com Free App

 

Mine has done it since new. I just ignore it.

 

I guess there is some comfort in knowing I'm not the only one that has had this for years. LOL Didn't mind the wait to OT when I was living in north GA, but Orlando is a different story!

 

Total theory, maybe when the engine heats up it allows more oil that is coating the piping to drain into the compressor for a less sloppy start up.
If that's true it would be better to wait for OT.

 

Don't quite understand that theory...why would the oil drain when its at opperating temperature and not with the vehicle just sitting there?

 

When you shut it down The oil is vaporized or mixed with the gas and coating the walls of the entire system. If you open the system after shutdown the walls of the pipe are coated with oil and a cotton swab proves this and It didn't run down the vertical pipes to the compressor or at least some.
Maybe when the engine warms it warms the oil on the pipes to be viscous enough to run down to the compressor at the bottom.

Short answer to your direct question is oil is more viscous when warmed. It's vaporized upon shutdown and cooling rapidly.

 

I had the same problem with my 07 5.9. Had to replace the compressor to solve the
problem.

 

I have this exact same problem. I get the loud clunk when I first turn on the ac but I can almost immediately turn it off and back on and I get a smooth engagement. The ac works really well so I guess I can sleep a little better knowing I'm not the only one.