Error code F42 Hera -80degC freezer

[Tesla]

I had a service call to this -80degC freezer and found the condenser blocked with a disintegrated filter which I cleaned. There is an error code F42 showing. I switched it of for some time and then on after a minute or so the word OPEN shows on the display and beeping noise, I checked the door reed switch = OK, Push any button and that clears and a moment later the F42 is displayed with the beeping noise. I have checked online and cannot find a service manual (or one in English) that will tell me what this code is or how to reset it. Any help will be appreciated.

Type HFU 686 Basic
Heraeus

[install monkey]

sorry tesla - i cant find manuals,only brochures- fisher scientific supply the cabinets and they have a technical dept heres the link http://www.fisher.co.uk/index.php/en/technical-support?view=ticket&layout=open

[Brian_UK]

I can find a manual but it is only in German.
http://www.thermoscientific.com/ecomm/servlet/techresource?storeId=11152&langId=-1&taxonomy=4&resourceId=95829&contentType=User+Manuals&productId=12811516

Translation..
Door or lid open:
Display: oPEn
Open the door or lid of time to be
from the control system registers.
After two minutes, a visual
(Open mode indicator) and an audible alarm
(short beeps) output.
OPEn the display goes out when the door or the
Cover within the next 2 minutes closed
is.
After 4 minutes, a long beep and the
F42 error message is output.
+++

So the door has been open for more than 4 minutes or the door switch is broken.

Oh thanks for Google Translate in our hour of need. ;)

[Tesla]

Thanks very much Brian and Install Monkey
I checked the door reed switch which checked OK, it could be the connection to the PCB or a component on the PCB which I shall check further.