Big "clunk" after start up - ???

[Walker]

After having my "reflash" done a couple of weeks ago, I now have a very distincitive "clunk" (which happens to sound similar to the a/c compressor "clunk/bang" when engaged, which I do have), and happens just about one second after start up. Sounds like its coming from the engine compartment (lower right/pass. side). My a/c unit is always off on start up so... Any ideas? It definitely was not an issue before the update.

 

[Giachino]

Mine does the same thing..... i think it is ac related... . typically i've had my ac on near shut down time... . and when i startup it happens (even if the ac is now off)..... it's not all the time, but it's also never happened when i'm not using the ac at all.

 

[Pawpaw]

If your heater control is set to defrost or defrost/heat blend, then your AC compressor will cycle. It's used in defrost mode to help dry the air before blowing it on your windshield.



Bob

 

[mconstable]

If your blend door is going south (mine is), it clunks pretty good.

next time you turn off the truck, make sure the fan (A/C) is off...

Next time you start it, after it's started, turn just the fan on low, wait a few seconds and see if it clunks, if so, that's the culprit.

 

[JEstes]

Somebody correct me if I'm wrong, but doesn't the truck turn on the compressor to help it warm up sometimes? I'm not 100% sure, since I haven't really looked into it, but I think mine does that occasionally.