When i turn on the AC/Heater blower on my 2010 Dodge Grand Caravan it make a clunk-clunk- clunk sound for 10-20 sec then runs as normal... What cound be causing this start up sound? Thanks

yes your ac compressor is kicking on. when you have defrost on it will kick on and off also...

The blower motor shaft suffers from lack of lube, water entry, or excessive bushing wear. after it runs awhile it may displace the problem, or find a smooth path to run. leaves, debris or mouse nest may be found in the heater area. wear gloves when accessing.

The movement of the plenum parts in the heater case can make strange sounds. I hear these unusual noises sometimes and have to check operation. If it does what it is set for, I leave it be. If I want to not hear certain sounds from one, I investigate. after understanding its normal operation and verifying it ? It could just be an amc or a mopar. Does it malfunction?

Stored vacuum in a reservoir can keep your settings but eventually it comes to rest after vacuum is bled off. when you restart later ? the vac can pull the parts to where the controls are set. I suppose you could see if your sound comes from a linear electric motor or activating a vac diaphragm.

When the controls were set to a different condition, the sound may not happen, that's an easier thing to try.

There was a message sent but no post here about the electrics in the actuator and limit vs. available linear distance in the actuator. It occurs to me if you verify your actuator sits and ratchets for very long at each direction? you must take it to your service department. one guy was saying his had been replaced once. but still reverted to this action. If an update of info, parts or a bulletin was to be found, you need to ask a service advisor at your dealer, show them, and see if they think it needs any help? or if there were a bulletin? ratcheting at the stop for several seconds and up to 20 sec? I think they should have your answer.

They may also say, yea, they do that. let me run a request and see what if anything is possible. You can get it on a repair order during coverage in case it decides to stop working. Or if you find a fix later you have it documented?

He said during movement of fresh air/recirc door, not temperature blend door so showing the service advisor or tech may be necessary, and ask parts if the number is replaced with an updated part, aside from a tech bulletin. Their procedure would be unknown to me exactly.

the damper for outside air vs recirculating inside air damper is getting hung up. probably a piece of an old filter or insulation making it hang up while the door is moving, thus the gears are jumping. left in-addressed will result in eventual stripping of the nylon gears and the damper door will be stuck in one position or another. you will have to take half the dash apart to service it. and I recommend a extra set of hands to hold up parts while inspecting and doing the repair. be prepared to have to order new gears and or actuator.

Take off your blower motor reach up in there and pull off your blend door reverse the order just take your glove box off save yourself some money