When doing a custard I noticed that my TM is not heating up fast enough.

As a reference test I boiled 1000 ml of water to 100 C.
According to the book this should take 5 min.
I only got to 80 C in that time.

I did this 2 x with the same result just to make sure.

Q:
How many heating elements in the TM?
and if there is more then one is it possible that one fails and the TM keeps on working?
Any other hints or ideas what is happening?

(Contacted our Sales Person, just no answer yet, maybe the forum is a quicker way to get an answer)

Thanks all
Romano