Repair 7

How to Check the Voltage on a Glow Plug

Glow plugs are used in vehicles that require diesel fuel to operate. Because glow plugs are exposed to extreme heat they can lose their voltage and become damaged quickly. If your cars glow plugs lose their voltage, you may find that your vehicle no longer starts. Even if the vehicle still starts, you may find that there are other operating issues. While a glow plugs voltage is usually checked by a professional in a garage, it can be done at home with the right equipment.

Instructions

1

Open the car hood and locate the glow plug relay. The glow plug relay is often found on the drivers side of the car behind the headlight. The location of the glow plug relay will depend on the vehicle. Glow plug relays are usually large, black and boxy, with a sticker that resembles a barcode. Several wires are attached to the glow plug relay.

2

Remove the glow plug relay lid and set aside. You will see several connectors and thick wires under the lid. Remove the largest connector by pulling up.

3

Set the multimeter to "ohms" and note the number on the display screen. That number must be subtracted from each glow plug voltage reading to get accurate results.

4

Connect the negative wire on the multimeter to the battery negative. The multimeter should be clearly labeled. Connect the positive wire to the multimeter and then insert the other end into each hole on the glow plug relay connector.

5

Read the meter to determine each glow plugs voltage. Refer to your vehicles user manual for recommended voltage levels.