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Saturday, 7 December 2013

Problem: The roaster will not light or the flame goes out during the roast.

Troubleshooting roaster ignition

Originally From Diedrich's old site:


Key locations for cleaning are:

  • The lower chaff compartment
  • The drum chaff tray
  • The cooling bin screen
  • The blower impeller
  • The rear chaff collector duct
  • the chimney (from the down pipe of roaster to the top of the chimney)

Tools Needed

  • One small Flathead Screwdriver
  • One small Philips Screwdriver
  • One Wire Brush
  • One Putty Knife
  • One small Pipe Cleaner or Paper Clip
  • Electrical meter


This is a classic symptom of an airflow issue. With this sheet you will be able to determine whether or not the symptoms are related to compromised air flow.

If your machine does not light, try making an air adjustment. With your machine turned on, move the air flow control from the cooling bin position to the 50/50 position. If the gas ignites you have proven there is an air flow or cleaning issue.

The burners going out during a roast and long roast times can also be signs of airflow problems.

With the burners lit, open one of your burner access doors. If this has either a positive or negative effect on the burners such as brighter burners (or dimmer) it is definitely airflow related.

From the roaster to the top of the chimney, all of these separate components combine into a balanced air flow system. Residue built up anywhere in the roasting system can affect the roaster’s function. This build up of residue will cause the airflow to be diminished, shutting the gas flow down to your burners. There can be a build-up of residue on impeller blades, air flapper, exhaust ports, etc.

Foreign objects in your chimney can also hinder the correct amount of air flow. Check for water dead birds, or other animals that may have got in there anything that impeeds airflow causes this problem.

Problem: Roaster Thermocouple or High Limit failure

Taken from the old Diedrich web site, which has been replaced:

If the roaster goes out and can be relit by resetting it; locate the Watlow high-limit. It is a small, black plastic molded box approximately 4 inch x 2.75 inch. In a manual roaster, it is located behind the switches in the electrical box. In an automated roaster, it is in the automation lectern.

Tools Needed: 
Electrical jumpers
Voltage meter
Flat head screwdriver
Phillips head screwdriver

REMOVE the red and yellow wires that are attached to the thermocouple terminals. Place a jumper or loop between the TC (+) and TC (-) on the high limit in place of the wires. If the roaster lights and stays lit, the cause is either a bad thermocouple or a loose connection between the thermocouple and the high limit. Check the connections before replacing the thermocouple.

If the roaster continues as before, goes out but relights upon resetting now you ll need to check the high limit.

Find the normally open or NO terminal and common or COM terminal. Put a jumper between those 2 terminals WITH the wires in place. If the roaster now stays lit the high limit has failed and needs to be replaced.

WARNING! Remember that this is a trouble shooting guide ONLY. Do not run the roaster with the high limit disabled. It is a substantial, safety hazard to do so and Diedrich Manufacturing, Inc. cannot be held responsible if damage occurs as a result. Be sure to reconnect the high limit before using the afterburner.