07 ram 1500 5.7 thump noise if heaters on

[Hesabiggin111]

I recently picked up an 07 dodge ram 1500 quad cab with the 5.7l hemi and when I have the heater on it randomly makes a thump sound possibly on the passenger side low and deep in the dashboard or possibly the engine compartment passenger side and it would have to be close to the firewall. Also it's kind of a low sound as if someone's thumping on a empty coffee can while hiding under my truck. It's not loud enough to know if it does it while driving and my AC and heat seem to blow fine. It definitely doesn't sound like air bubbles in the heater core could it be a vent door? Thank you for any advice

 

[Fast69Mopar]

I recently picked up an 07 dodge ram 1500 quad cab with the 5.7l hemi and when I have the heater on it randomly makes a thump sound possibly on the passenger side low and deep in the dashboard or possibly the engine compartment passenger side and it would have to be close to the firewall. Also it's kind of a low sound as if someone's thumping on a empty coffee can while hiding under my truck. It's not loud enough to know if it does it while driving and my AC and heat seem to blow fine. It definitely doesn't sound like air bubbles in the heater core could it be a vent door? Thank you for any advice

Without seeing the truck or a video of it happening my best guess would be a broken recirc. door.

When you hear the thump sound do you hear it once or is it continuous?

Does it get louder while driving a certain speed?

Can you duplicate the noise multiple times by doing something specific?

 

[CorDog009]

Blender door. My truck does the same thing. Luckily mine is just the one that lets fresh air in, so there's always a slight bit of air coming through the vent with the blower motor is off, ambient air in the summer and warm air in the winter depending on the temp selector knob.

 

[cheffrank_357]

Broken or detacheched spring on the door
Not easy to get at btw
Just turn the radio up lol

Sent from my SM-G975U1 using Tapatalk

 

[Hesabiggin111]

Thanks for the responses I figured it was a vent door just didn't realize it would make the noise every few minutes. So wanted to be sure it wasn't something serious.