Pulsacoil 2000 help - thermostat settings / reset buttons / + -

Hi, first time poster so thanks for help in advance.

I have pulsacoil 2000 system which was working fine - originally had problem about a year ago where system wasn't producing any hot water at all. Plumber came out and remove the thermostat covers and pressed the tiny black button and that did the trick- think this was a reset?

Over course of last 12 months I've had to do this myself once and it worked again.

Yesterday went to shower and water was only Luke warm. Went to press reset button and it didnt need to be pressed. The top thermostat black switch is set to the plus sign permanently ( I think this is max) but the bottom one has always been around the half way point. I turned this towards the plus sign and within 30 mins I had nice hot water again.

Rang plumber and he said my two immersions need changing n all set to charge me 350£ for pleasure. Can someone please tell me if I need them changing or is it ok to have the bottom thermostat switch on the plus sign all the time?
Any help be muchly appreciated
Thanks

The stats need to be set at about 72c
I work on lots of PC 2000's.
And the genuine Gledhill immersion heater are the best.
And their rod stat DO NOT HAVE RESET BUTTONS.
Being a thermal store heating up to 72c.
The DHW is sorted out by the sensors, pump and PCB. (50 to 55c)
If your heaters are ok.
Then get 2 new rod stats.
Mike

Sorry Mike, the later Pulsacoil 2000 have the rod thermostats XB081( the green one, not the blue one) with the black knob ( reset button) fitted ( factory upgrade to remove the central overheat thermostat GT064), but yes also those are calibrated to 72 centigrade and like to pop out ( mostly do to a leak at the stat pocket) , if they do ( only pop out and not leaking, so the back cap cover is dry inside), change the stat, but otherwise if they are not pop out and the unit is not heated on the Off peak , there is a good chance, the immersion is gone.
regards Mario at Mario's Boiler Service

The newer ones do have reset buttons. JB is the cylinder hot? Check the water level in the header tank if it is. Also it may not be the element but could be the pump or sensor, agree with the contractor you are using to check they system in case it is not the element.