This post is to assist others that are having problems with G1800 temperature and/or fuel gauges that will not work, or work intermittently. While electrical problems are usually suspected, it has been noted on my unit and others (Phil) that the needles of these gauges are actually getting stuck to the posts, and the solution is to dismantle the instrument panel and correct the problem.
Still, certain electrical problems can cause these same issues, and after reviewing the schematics that "Jinman" was kind enough to forward, I think a couple of easy "checks" can be made to rule out electrical problems.
I am no expert on this subject, and would invite other forum members to weigh in on my logic if any part looks incorrect or needs clarification.
Each of the gauges has three wires attached; two are common to both gauges.
The third wire from each is unique to that gauge and goes to either the temperature sending unit or fuel sending unit, where resistance is measured.
12volt DC + leg to gauges: if the "oil" (and glow plug) light is still working when the key is turned to the on position, then the gauges will be getting power, so you can rule that out as a problem.
12volt DC - ground leg to gauges: If the two instrument panel bulbs still work that light the panel (sorry, I do not remember if the headlights have to be turned on, but try it both ways) then your gauges should still have this shared ground leg, and so ground or common to the gauges should not be the problem.
Wires to sending units: If it appears you have both 12volts + and - from the above checks, then with the key on, momentarily remove the wire from each sending unit and touch to ground, to see if the gauge reacts; if it does you could have sending unit issues.
If you get no reaction from grounding the sending unit wire, then there is an excellent chance your gauge needles are simply stuck to the posts, so you may wish to proceed to dismantle the instrument panel and correct that problem.
Still, certain electrical problems can cause these same issues, and after reviewing the schematics that "Jinman" was kind enough to forward, I think a couple of easy "checks" can be made to rule out electrical problems.
I am no expert on this subject, and would invite other forum members to weigh in on my logic if any part looks incorrect or needs clarification.
Each of the gauges has three wires attached; two are common to both gauges.
The third wire from each is unique to that gauge and goes to either the temperature sending unit or fuel sending unit, where resistance is measured.
12volt DC + leg to gauges: if the "oil" (and glow plug) light is still working when the key is turned to the on position, then the gauges will be getting power, so you can rule that out as a problem.
12volt DC - ground leg to gauges: If the two instrument panel bulbs still work that light the panel (sorry, I do not remember if the headlights have to be turned on, but try it both ways) then your gauges should still have this shared ground leg, and so ground or common to the gauges should not be the problem.
Wires to sending units: If it appears you have both 12volts + and - from the above checks, then with the key on, momentarily remove the wire from each sending unit and touch to ground, to see if the gauge reacts; if it does you could have sending unit issues.
If you get no reaction from grounding the sending unit wire, then there is an excellent chance your gauge needles are simply stuck to the posts, so you may wish to proceed to dismantle the instrument panel and correct that problem.
