2. If the preheater begins to malfunction, it can only be checked accurately enough by trial replacement of the questionable components. However, you can do some preliminary checks.
3. Disconnect the main supply wire from the corresponding candle (see photo).
4. Connect a voltmeter between the supply wire and "earth", making sure that the wire does not touch the engine and the car body. Ask an assistant to turn on the preheater and check that the voltmeter shows 12 V for several seconds before the system turns off automatically. As a rule, at an air temperature of + 20°C, voltage should be applied to the candles for 7 seconds. This time decreases at higher air temperatures and increases at lower ones. If the voltmeter does not show voltage at all, then the reason for this may lie either in the relay or in the wiring. Switch off the ignition.
5. Connect an ammeter between the positive terminal of the battery and the wire connecting the glow plugs. Check that after 20 seconds each of the candles takes 12 A of current (those. only 48 A if all 4 candles work).
6. If one or more candles do not consume current, disconnect the wire connecting the candles and test them individually or use an ohmmeter to check the candles for continuity and make sure that they have the same resistance.
7. When finished, connect the main power cable.
Pre-start and post-start heaters (latest XUD9 engines)
1. On all engines, the glow plugs run for approximately 7 seconds before starting the engine. (The exact operating time of the candles depends on the temperature of the air under the hood).
2. The after-start heater provided on some recent engines ensures the operation of the candles for another 3 minutes after starting the engine (provided that the load lever switch contacts are closed and the engine temperature does not exceed 60°C). This reduces noise and smoke from the engine exhaust after a cold start.
3. See appropriate section for load lever switch adjustment.
4. Temperature control is carried out using a thermal switch behind the fuel filter housing (the thermal switch can be recognized by the pink-purple plastic ring).