Lee 420 pot wont go over 750 F

[Buttonbuck]

Ok so last time I cast the temp was about 50ish same as this morning. I usually run my pot at 750-800 for pure lead for muzzleloading roundballs and lee slugs. I put it on 10 and waited 25 min it went to 650, I backed it off and set it again at 10 it went to 750 I put it back on 8 and it stayed at 10. Is this a potentiometer or reostat? Do I just need to take it apart and spray it out with contact cleaner? anyone experience this? I keep the pot in the barn I should probably bring it inside.

[Frozone]

The controller is neither a "potentiometer or reostat" (they are the same thing BTW), it is an 'infinite control' often used on ovens and hotplates.

It works by heating up a bimetal strip as current pass through it. After the control reaches a certain temp it shuts off until it cools.
You can check it by opening the case and moving a wire from the control to the element (UM... unplug the thing first) cutting the control out of the loop.
If the pot reaches temp (and over as it's full on all the time) replace the control. If the pot still won't come up to temp replace the element.

[Maven]

Frozone's advice is excellent. However, before you do that, make sure the pot is unplugged, then try cleaning the contacts on that bi-metallic strip and gently bending the lower one down, by ~1/8". Plug it in again and see if the temp. rises above 750 deg. F. If so, you're fine. If not follow Frozone's advice.

[Buttonbuck]

Well before I disected the pot I tried it again. The Lyman thermometer read 750-800 f when I got blue and gold colors on top. I was thinking this was a physical change that occurs closer to 850-900? At any rate I am thinking that I had not run this pot in a few months and being in the barn it just got dirty. I think I need to keep it inside. Any Ideas on the thermometer if it is reading low? How do you test and calibrate these things.

[prs]

First good news is the parts are reasonably priced. Second goodie is that these are easy to service. No really bad news.

prs