2002 LB7 Glowplug relay melting

[LBZMike]

My brother inlaw has his 2002 Silv. HD (LB7) in the shop having the glow plugs changed. Has over 200k miles. The shop found out the bank on the right side(PS) was not working due to the relay wire being burnt in half. Replaced both banks. The left side is heating up the relay wire still causing it to get very hot and would proabably melt it thru. Mechanic is going nuts trying to figure it out. Any help is appriciated.:confused:

[rapidoxidationman]

An ohmmeter should find out where the short is... Or maybe just a REALLY bad connection at the relay is causing it to overheat.

[More Power]

Beginning in 2002, the LB7 glow system (at least the CA models) received individual wires running to each of the eight glow plugs, while each bank of the 2001 LB7 glow plugs were ganged together.

I would disconnect portions of the glow plug system looking for what's causing the excessive draw. A process of elimination.

Jim

[DmaxMaverick]

The emission series is important. All CA emission Duramax trucks have individual wires (my Oct. 2000 built truck does), while the fed emission trucks are grid wired (one power lead to each bank, with the GP's ganged, as MP said). If you are unsure which it is, there's a picture of a CA model GP controller in the "truck stuff pics" link in my signature. If yours doesn't look like that, then it's a federal smog truck.

Either way, there's only so many things that can cause an overload on the system. If it's a CA model, you can use a scanner to read the feedback voltage during a cold start. The voltage reading will indicate how many plugs are working, or if the number is off the scale, there is a short on at least one harness. Any condition not "normal" will illuminate the SES and store a "P0380" code. 2006 and later trucks will actually tell you which cylinder. The LB7 federal trucks aren't as smart, which isn't necessarily a bad thing.

Anyway, I suspect a dead short in the harness, or one glow plug that's dead-closed (shorted internally). I suggest removing each plug and put power to them. They should glow full in 10 seconds or less. If you have one that draws power but doesn't glow, that's the shorted plug. It should be quite obvious. I've not heard of this happening with the Duramax plugs, but it wasn't too uncommon on all previous thermistor-type plugs (11G and later).