Insufficient heat output

Step 1: Fuel pump

Check delivery quantity of fuel pump.

Possible defect	Remedy
Delivery quantity too small	Adjust delivery quantity
Filter blocked	Clean filter
Strainer dirty	Clean strainer
Fuel check valve blocked	Install new fuel check valve

Step 2: Temperature regulating system

Check temperature regulation.

Possible defect	Remedy
Check temperature sensor and temperature regulating switch	Replace temperature sensor

Step 3: Engine heat exchanger

Check adjustment of heater flaps on engine heat exchanger.

Possible defect	Remedy
Bowden cable adjustment not correct	Adjust

Step 4: Engine cooling air housing

Non-return flaps in engine cooling air housing stiff or jammed.

Possible defect	Remedy
Not installed correctly	Remove cooling air fan and check flaps. replace if necessary.