Clunking noise at start-up. Fan clutch?

[JBonpua]

I get this clunking noise within the first second or two after I first start the engine. It sounds like the magnetic clutch engaging the A/C compressor with a fan sound mixed in. It does it when I take out my truck once a week to go to church on Sunday morning (yes it is a Sunday truck). Throughout the day, I have not notice this sound. It seems like it only does it if it stays overnight. It sure sound like a fan clutch to me. How reliable are these clutches on a 3rd gen? What would be the symptoms of a bad clutch? I’ve also notices the fan been coming on a lot for no reason even when it is relatively cool out with no A/C and not towing (I don’t tow anything, remember Sunday truck). Any ideas?

 

[1smoknC]

yea mine does that too, but its not really a clunking noise. its more like a ticking and it lasts about 20-30 seconds and only happens after the truck sat overnight. its really weird.

 

[rbattelle]

I'd bet it's your A/C clutch coming on. The loud clunk is un-nerving, but normal.

Ryan

 

[WKruger]

I got the same noise. Sounds like it's coming from around the transmission. Sorry for the hi-jack.

 

[KWilkinson]

Does it do it no matter the position of the A/C blend/vent switch setting? If you have it set to the cold side you will get a clunk of the blend door slamming back and the ac clutch kicking on. When you shut the truck off the blend door moves back to a default center position and when you turn the key on and the ac clutch cycles the blend door moves back to whatever position the switch was left to, and if it is left on cold it makes a thump when it closes. Just try setting your ac to mid-range, see if it still does it.

 

[JBonpua]

I'd bet it's your A/C clutch coming on. The loud clunk is un-nerving, but normal.



Ryan

Does it do it no matter the position of the A/C blend/vent switch setting? If you have it set to the cold side you will get a clunk of the blend door slamming back and the ac clutch kicking on. When you shut the truck off the blend door moves back to a default center position and when you turn the key on and the ac clutch cycles the blend door moves back to whatever position the switch was left to, and if it is left on cold it makes a thump when it closes. Just try setting your ac to mid-range, see if it still does it.

This happens when the A/C is off so it would not be the compressor clutch engaging or the blend door. I will have to get my wife to start it while I'm under the hood (scary thought). I really believe its coming from the fan/clutch somewhere. My G56 and DMF is quiet so I don’t think it is that.

 

[rbattelle]

This happens when the A/C is off so it would not be the compressor clutch engaging or the blend door.

Is the vent control set to defrost?



Ryan

 

[JBonpua]

Is the vent control set to defrost?



Ryan

The vent is set to flow through the front vent with the fan switch off. The weird thing is today it did not do it when I was under the hood and my wife started the truck. #@$%! This thing is possessed!

 

[DBentley]

On my 96 and the 06 it sounds like someone hitting the block with a big hammer on startup. Im sure its the ac pump kicking in.

 

[MrFixit]

Went through this last summer when my truck was new. We took a 3k mile trip and when I 1st heard the noise, I started checking everyday upon start up to see where it was coming from. It was the A/C compressor. ECM progrmmed to engage A/C clutch for a second upon start up. I have a friend that works at Dodge that confirmed this.