Heater does not work at low outside temperature

Step 1: Battery

Measure battery voltage.

Possible defect	Remedy
Voltage too low	Recharge battery if necessary

Step 2: Fuel pump

Check fuel pump delivery quantity.

Possible defect	Remedy
Delivery quantity too small due to	Change condition by

Step 3: Glow-spark plug

Remove glow-spark plug and check glow element.

Possible defect	Remedy
Open in glow element	Install new glow-spark plug

Step 4: Thermo switch

Connect voltmeter to terminal NO of safety switch and to ground, then turn heater on with engine cold. Voltage must be held for at least 70 seconds.

Possible defect	Remedy
Thermo switch defective (cut-in time too short)	Install new thermo switch