Lately on startup I get an intermittent rattling/scraping sound. I thought it was the fan, then I thought it was the AC. Not the compressor, somewhere behind it I think.
Is it something a shot of coolant would take care of? AC seems to be cooling okay but outside temps have been low. https://photos.app.goo.gl/vHUP1iYCdDhCSY858

 

The picture is of the alternator. Shot of coolant?...you mean lubricant? Either way , nope.

There is an idler pulley that may be making the noise, pretty easy to replace, does require removing the serpentine belt...actually if you remove the belt, then you can spin the alternator and the idler pulley...see if either is making noise or spins with resistance. Again idler pulley easy to replace...alternator bearing not so much...I take to a shop, requires a press to get old bearing off, new bearing on...plus they install a new rectifier.

 

The shot was really to catch the noise. You can just hear it intermittently over the engine noise. It is coming from the back of the engine, towards the firewall. Actually it is quite noticeable from in the cab. Did not do it this morning though.

 

Is the AC compressor cycling on and off rapidly ? That is a sign of low R-134a refrigerant. Be cautious when using the AC Pro type DIY recharge kit. Be sure the can doesn't contain any sealant. the can should contain only refrigerant and oil---no sealant. If it does and later you have to take the vehicle to a shop, they will not touch the AC if it had any sealant in it. It fouls up their expensive AC purge machines. BTW yoiu don't have to use the AC Pro refills when you exhaust the initial can of AC Pro. You can buy the small size cans and they are more likely to have just the refrig and the oil without the ealant. These small cans of R-134a are under $10 an be bought at any Auto supply store.

 

I do not recommend using the DYI cans of refrigerant because there is no easy way to vent the air out of the hose between the can and the valve that connects to the vehicle's schrader valve, so this introduces air into the system. I know it is not much air, but still.
And I double agree that if the can contains sealant, then no shop will connect their equipment.

As far as the noise...check the distributor cap, rotor...make sure they are tight. If those are good, and you still have the OEM distributor, the one with the plastic housing....it is very likely shot.
Also, I had an aftermarket cap/rotor at one time...there was a clearance issue with them...the rotor was rubbing on the cap. Replaced with Delco...problem gone.

Later,

 

If this video works can anyone interpret the rattle noise at about one second? Note the AC is off, actually.
https://drive.google.com/file/d/17Nf...w?usp=drivesdk.

 

Unable to help, as I do not have a Google account to view video.

 

Sorry Lanny, I can't get the sound for you. Oh well, maybe it will go away by itself...