So I’ve been trying to figure out what is up with my heater. Its newly installed but out of warranty as I bought it a year prior on a sale.

The unit had been working great for a couple months heating my spa. This is a Pentair Mastertemp 125.

One evening my wife mentioned it was cold even while running and sure enough the heater was showing a service heater light. So I reset the heater and it came on, sounding normal, blower spinning up, hear it ignite and run for about 5-10 seconds then something clicks and the whole system whines and shudders.

I did a bit of testing and from what I can tell its worse when it gets hot, if I start it colder it will whine and then stop until it gets hotter.

Waterflow is not restricted, there are sensors that measure water flow and the burner won’t fire if the flow is too low, it feels the same at the exit and the temp when running isn’t hotter when exiting.

I pulled the blower apart and confirmed there is no obstructions or loose parts.

I’ve bypassed the pressure switch as well to test if this was the issue.

I’ve also talked to Pentair who isn’t so helpful (they just want me to get a tech out)

I’m really hoping you might be able to point me in the right direction for what I might look into.

I have a link of a video of the unit when it engages, in the video the blower is running and the igniter is already on and about 5 seconds in you can hear it start groaning and then slowly get better.

any help would be appreciated, I’m pretty handy if I know where to look.

Thanks!