4-52 4181384 First Edition
ELECTRICAL
4
Glow Plug Circuit
Symptom: Glow plugs do not get hot.
Symptom: Glow plug wait light does not
come on.
Probable Cause Remedy
Faulty power circuit. Measure voltage between 40A fuse F12 brn wire terminal and ground. Voltage must be
approximately 12 VDC.
Open 40A fuse F12. Test fuse. (See “Fuse Test” on page 4-61.)
Faulty glow plug relay power circuit. Measure voltage between 40A fuse F12 brn/wht wire terminal and ground. Voltage must
be approximately 12 VDC.
Faulty glow plug relay. Test relay. (See “Relay Tests” on page 4-62.)
Faulty key switch. Test switch. (See “Key Switch Test” on page 4-63.)
Faulty key switch circuit. Check continuity between key switch terminal 19 and glow plug relay terminal 86.
Continuity must be indicated.
Open glow plug relay ground circuit. Check continuity between glow plug relay terminal 85 and ground. Continuity must be
indicated.
Faulty glow plug relay output circuit. Measure voltage between glow plug terminal strip and ground. Voltage must be
approximately 12 VDC.
Faulty connection at glow plug terminal
strip.
Clean and tighten ring terminal connector.
Probable Cause Remedy
Faulty glow plug wait light. Check light bulb and connections.
Faulty glow plug timer. Substitute the timer with a known good glow plug timer.
Faulty key switch. Test switch. (See “Key Switch Test” on page 4-63.)
Faulty glow plug timer circuit. With the key switch in the heat position, measure voltage between glow plug timer
terminal 4 and ground. Voltage must be approximately 12 VDC.
Open glow plug timer ground circuit. Check continuity between glow plug timer terminal 3 and ground. Continuity must be
indicated.
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