753 Bobcat Glow plug?

[DaleM 753]

Hi All, I have a 1991 Model 753 (508613765). My glow plugs are not working and I'm just starting into my troubleshooting. On my machine, when I take my key to ON, after the initial display light-up, my glow plugs will automatically come on for a timed duration if the coolant temp is cold enough. If so, the display will show GLO XX with the XX being the seconds the plugs will be energized - 5, 10, 15, etc. This part seems to work fine as I see the plug countdown when temps are cold. I do NOT, however, get voltage at the bus bar across the plugs during the countdown. From what I've read, there is typically a relay feeding the plugs. My O&M manual does not tell me where that relay is. I have several relays in the engine compartment under the air cleaner, and also some off the cab harness mounted on the back of the cab near where the "computer box" (not really sure what it is) mounts. Short of tracing wires, any way to know what relay feeds my plugs? Aside from the relay and bad connectors, any other starting point suggestions? Thx all. Dale M

 

[reaperman]

You need to find a manual to look up the schematic diagram. I thought those older c series glow plugs were activated by turning the key backwards? I may be thinking of the 743 series.

 

[DaleM 753]

Thanks Reaperman, it might be worthy me buying a service manual as I'm sure it wont be the last time I need one. My glow plugs work for certain as I described. I can see the GLO XX display and countdown working on my little diagnostic panel when I take the key to ON. Just no voltage. I'll see if I can chase some wires and figure out which relay is associated.

 

[reaperman]

There are manuals on this site that can be view and possibly downloaded, do a search. I haven't looked on this site but have read of other members using them.

 

[DaleM 753]

Just a follow-up for someone in the future searching for this info. The Glow plug relay, as well as the starter relay and two fuses, are all mounted on the same bracket under the air filter in the engine compartment. The two relays are the same. I swapped my starter relay into the glow plug relay port and the glow plugs worked as they were supposed to. 12VDC at the glow plug plug bus bar until the instrument panel countdown was done, then 0VDC. Hope this helps. Dale M