Cummins/Onan — Heater (Glow Plug) Relay Check (K13)
Testing & diagnosis · Glow plug heater relay K13
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan HDKA, Cummins/Onan HDKAQ, Cummins/Onan HDKAR
Procedure
- Connect the relay coil voltage across the relay coil terminals; the relay should activate if coil is okay.
- Connect a voltage source to one side of relay contacts.
- Connect a voltmeter to other side of relay contact and voltage source.
- If voltage appears when relay energizes, the contact is good.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan HDKA →, Cummins/Onan HDKAQ →, Cummins/Onan HDKAR →
Source: Cummins/Onan service 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.