Electrolux grill not reaching max temperature?

I have an electrolux built in oven.
When I switch the grill on and turn the temperature to Max it will only reach 150 degrees (I know this as when you turn the temperature back down to 150 degrees the light indicating that the grill is still heating to the required temp goes out).
I have two options - full grill and half grill and the same happens on both (there are two elements).
The oven however heats to max temp with no problems.
If it was an element, surely one of the grill options would work?
Is there a separate thermostat for the grill, from the oven?
If so, am I correct in assuming it is the thermostat?