Problems with starting a diesel engine in cold weather most often arise due to glow plugs. These parts are responsible for quickly warming the air in the combustion chamber, which facilitates starting the power unit. When at least one such element fails, the diesel starts with difficulty, vibrations and thick exhaust appear. To avoid this, it is useful to be able to independently identify the malfunction. In the material, we will analyze how to check glow plugs with a tester, a light bulb, a battery, and a multimeter, and also talk about diagnostics without removing them from the car.

Why checking glow plugs is necessary

On diesel engines, the serviceability of glow plugs determines how easily the engine starts in winter. If the entire system works as it should, the unit starts without extra effort even in severe frost. When a plug burns out, the fuel mixture does not ignite in time, and the engine begins to misfire. Timely diagnostics helps to detect the problem in advance and install a new plug before the cold weather arrives.

How to check glow plugs without removing them from the engine

Many car owners wonder whether it is realistic to assess the condition of the plugs without removing them. Yes, such an option exists. The most common method is to use a tester or multimeter. You just need to connect to the plug contacts and measure the resistance.
  1. Turn off the engine and disconnect power in the onboard network.
  2. Connect the negative probe of the multimeter to the car body (ground).
  3. Touch the positive probe to the plug contact.
  4. Compare the obtained data with the norm: for a working plug, the resistance value usually stays in the range of 0.5–2 ohms.
  5. If the device shows infinity or too high a value, the element is faulty.
This approach allows you to quickly assess the condition of the plugs directly on the car.

How to check glow plugs with a multimeter

Using a multimeter is considered the most accurate diagnostic method. The procedure is as follows:
  • Switch the tester to resistance measurement mode.
  • Disconnect the power wire from the plug.
  • Place one probe on the plug body and the other on its contact.
  • A working plug will show low resistance (about 1 ohm).
If the resistance is noticeably higher or the multimeter shows infinity, the part needs to be replaced.

How to check glow plugs with a tester

The tester, also known as a multimeter, is a universal device. In addition to resistance, you can also measure current consumption:
  1. Connect the ammeter in series to the plug power circuit.
  2. Turn on the ignition.
  3. A working element should consume from 8 to 15 amperes.
When the current is too low or absent altogether, the plug is not functioning.

How to check glow plugs with a light bulb

A more accessible method is using a test lamp.
  • Connect one contact of the lamp to the battery.
  • Connect the second contact to the plug terminal.
  • If the lamp lights up, the plug is fine; if not, it is burned out.
This method is convenient for a quick check, but it is less accurate than a multimeter.

How to check glow plugs with a battery

Checking directly from the battery is also permissible, but caution is needed here.
  • Remove the plug from the engine.
  • Connect the battery negative to the plug body.
  • Apply positive to the contact.
  • A working plug heats up very quickly and begins to glow red.
This method allows you to accurately identify a non-working plug, but it requires removing it.

How to check glow plugs on a diesel without removing them

For diesel engines, the ability to diagnose without disassembly is especially valuable. That is why a multimeter is most often used. It allows you to assess the condition of the plug directly on the car without resorting to removal.