Caterpillar 3406 — Check Glow Plugs
Testing & diagnosis · Starting Aids
For the Caterpillar 3406, from the Caterpillar operator's manual.
Applies to: Caterpillar 3406
Procedure
- Disconnect the wire lead from the glow plug terminal on the HEAT-START switch.
- Install an ammeter with a capacity of over 75 amps, in series, between the disconnected lead and the terminal on the HEAT-START switch.
- Turn HEAT-START switch to HEAT.
- Observe the ammeter. Each 12 volt glow plug draws approximately 12.5 amperes. The ampere draw of one glow plug multiplied by 6 will be 75 amps, the total ampere draw of the glow plugs in the engine. A
- If a defective glow plug is indicated, disconnect one glow plug lead at a time.
- Turn switch to the HEAT position. Observe the ammeter. Reconnect the lead.
- The glow plug that does not change the reading on the ammeter, when the switch is turned on, is the defective glow plug.
Tools required
- ammeter with capacity over 75 amps Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Each 12 volt glow plug draws approximately 12.5 amperes.
- Total ampere draw of the glow plugs in the engine is 75 amps.
Full service-parts list: Caterpillar 3406 →
Source: Caterpillar operator's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.