This 1994 suburban 6.5 TD, has been sitting for 8 years, now has a new engine, everything was functioning before, now the glow plug light doesn't work. The dash is apart and I have been looking for the glow plug fuse, no one knows where it is, and have been testing the wiring, no connection from the instrument panel to the glow plugs. There is no photo nor wiring diagram of the firewall junction box on the internet. Their have been suggested alternative fuses, but all are OK. Can anyone diagnose the position of the failure?
grancito
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This 1994 suburban 6.5 TD, has been sitting for 8 years, now has a new engine, everything was functioning before, now the glow plug light doesn't work. The dash is apart and I have been looking for the glow plug fuse, no one knows where it is, and have been testing the wiring, no connection from the instrument panel to the glow plugs. There is no photo nor wiring diagram of the firewall junction box on the internet. Their have been suggested alternative fuses, but all are OK. Can anyone diagnose the position of the failure?
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Thread from the 6.5L FAQ page may guide you: My glow plugs won't cycle
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Coming off the GPR there is an orange wire in the loom heading off to the drivers side. Possible you have a break in that wire some place?
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Thank you for the diagrams, I'll start by trying to find that fuse again, they were all OK but none labelled glow plugs. The bulkhead connector image is confusing, but I will go back to the fuses.
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I started untaping the loom to find the connection, but was going to make a real mess, and did not get to the connection point. Hit and miss circuit testing the bulkhead connector, got me nowhere, the position is difficult for me to access. The wire could be disconnected at the orange lead, the engine has just been replaced and wiring had to be move out of the way.
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Try checking for a blown GLOW PLUG fuse or bad WTS lamp bulb.
Check the dash ground wire above the DLC.
The GLOW PLUG fuse will only have voltage while the glow plugs have voltage.
The GLOW PLUG fuse does not have anything to do with the function of the glow plug relay.
Check the dash ground wire above the DLC.
The GLOW PLUG fuse will only have voltage while the glow plugs have voltage.
The GLOW PLUG fuse does not have anything to do with the function of the glow plug relay.
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Ok, I found the fuse, no label for it, it is OK. I have checked from the ECM, the instrument panel circuits, the plug connection and obviously the bulb, and now find there is connection to the instrument panel from the fuse. I was looking for the dash ground but could not find it, anyway the tests excluded a ground problem. The fuse to glow plug wires has no voltage when the plugs are on. So the problem is the connection in the harness or the bulkhead junction. I still have not got a wire colour diagram of the junction block. It is too hot to work here, 94 F, it will cool down in a few days, we have rain and a cyclone coming, so I will wait for info and get back to it in a few days.
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Follow the driver side glow plug wires and just about where they enter the main harness will be a large splice with heavy orange wires.
One of those wires goes to "B1" on the firewall conn. (C100).
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One of those wires goes to "B1" on the firewall conn. (C100).
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I followed the large orange wire to the bukhead juntion area, it has connection to the glow plugs, before it disapears with the other wires into a mess of tar type sealant. After getting the soft cover off, I found no access to any connections. The cab side of the box does not look like the drawing and I was unable to determine which wire could be the glow plug one. It is very difficult for me to remove each plug, so have only removed those that could be the one, by position and colour. Next I will try to feel behind the fuse block for the glow plug fuse wire, to track it. The block wont come out or turn over after disconnecting it. It got twisted and was ulmost imposible to clip back in place. Failing success there, I will drill the fire wall and run a wire from the glow plug relay to the front of the fuse block. It is not so hot now, so can do a small amount of work.
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The cab side of the C100 connector has the convenience center over what is shown on the diagram.
The conv. center can be released from the C100 conn. to get at the wires coming thru the firewall conn.
The conv. center can be released from the C100 conn. to get at the wires coming thru the firewall conn.
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Thank you, now I understand, the last photos are of the junction inside the cab, I was testing the wrong connectors. I got a look at the back of the fuse block from under the dash and see the orange wire I have so much bleeding under the arm skin from so much difficult positions, I am going to cut the wires both sides and make a link through the fire wall.
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Thank you for your help with the photos and diagrams, I went with the link, from near the junction box in the engine compartment, to the back of the fuse board, throught the hood release grommet. I broke a piece of the dash board while releasing it to get to the back and turn it slightly. A difficult repair to the fuse block and a lot of bad words for the designers. The light works, so now back to assembling the dash.
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