best to get it checked by gas safe engineer[UK]who can also work on LPG equipment. First contact Truma ask if flame should rise as control knob is turned or does it ignite a second row of jets on same burner bar.
In case you haven't Truma contact details.
Contact Details:
Email technicalATtrumauk.com
salesATtrumauk.com
ON EMAIL ADDRESSES CHANGE THE AT TO NORMAL EMAIL SYMBOL AS THIS FORUM DOES NOT ACCEPT EMAIL ADDRESS IN NORMAL FORM.
Website www.trumauk.com
Telephone 01283 586050
Fax 01283 586051
Address Truma UK Ltd
Park Lane
Dove Valley Park
South Derbyshire
DE65 5BG
Bob, May 2011