Intermitent electircal malfunction?

[RDrancher]

Three times in the last week my tach has been dead on start-up, then starts working and stays that way all day. Yesterday the temp gauge quit working about two hours into a job, then started working a couple hours later.

Any ideas?

 

[murphy1244]

Maybe bad grounds. Those types of problems are tuff but it is usually a ground.

 

[RDrancher]

Thanks Murph, I'll check it out.

 

[Spicer]

At this point I cannot tell you what is going wrong. I can give you the theory of operation.

None of the gages are directly connect to the sensors. The MPU reads the individual sensors and outputs to the dial gages.

All of the dial gages are biased to give the indicated measurement. Each gage has two windings; one set moves the needle up and the other down. If the needle is at the half way point both windings have the same rms voltage applied on both sets of windings. The MPU provides the biasing.

The Tach and the Temp appear to have independent failures. My only suggestion at this point would be to cycle the power by removing a battery terminal for at least 30seconds.

The next time the tach fails check if the hour meter is incrementing the last digit (illustration of an hour glass) every 36 seconds.

Mike

 

[Spicer]

Are there any common connection points on the PCB such as ground or +12V?

The Temp and Fuel gages are common ground, but the tach is common positive.

Mike

 

[jinman]

My tach and fuel gage stick at zero all the time. Sticking of gages that experience condensation is common. I just give the face of my instrument panel a good rap and the tach and fuel gage spring to life. I just love smackin' that tractor. It makes me feel good and people call me Fonzi.

 

[RDrancher]

My tach and fuel gage stick at zero all the time. Sticking of gages that experience condensation is common. I just give the face of my instrument panel a good rap and the tach and fuel gage spring to life. I just love smackin' that tractor. It makes me feel good and people call me Fonzi.

I knew you'd be along with an ultra-technical fix.

I got blown out of my job this morning when a backhoe hit a water line up the bank from my grading area. Figured I'd trailer up, head home and do my weekly pressure washing and general look-a-round-for-loose-stuff. While I was at it I removed and disconnected the gauge cluster, and cleaned up the contacts. It always amazes me how filthy it gets behind the gauge cluster.

Maybe I'll just apply the "Fonzi love tap" method of repair and call it good.

 

[jimmysisson]

" do my weekly pressure washing " Maybe some water or cleaner is getting in where it corrodes contacts? I like clean too, but I'd hand wash the dash electrical area. $.02
Jim

 

[jinman]

" do my weekly pressure washing " Maybe some water or cleaner is getting in where it corrodes contacts? I like clean too, but I'd hand wash the dash electrical area. $.02
Jim

Jim, from my experience, it's not external water that gets into the instrument panel from the top because it is sealed pretty well with a gasket to the dash panel. Since they are not hermetically sealed, the outside air is free to collect inside the panel from the bottom or back side of the panel. When it is humid during the daytime and then cool at night, I see condensation on the inside of my panel from the trapped humidity. I think that's common with tractors of several brands that use the modular instrument panel designs. If there was a fan drawing air through the panel, it would reduce the collection of moisture, but then there would be dirt (lots of it) unless you had a filter. . . and it goes on and on.

On our tractors, the temperature gage and fuel gage are about $70 each and the tach is about $135. The whole instrument panel is about $790, so replacing the individual gages is the best if that will fix the problem. The crazy thing is that the deluxe model tractors have three gages and the non-deluxe models have only a fuel and tach (no temperature gage), but the non-deluxe instrument panel is over $900. Sheesh!

On the 2120, the instrument panel seems to be more vertical than ours and may direct condensation away from the actual instruments. Ours is more horizontal and moisture off the lens drips right down onto the gages. BTW: Have you ever looked at the prices on replacement parts for your panel? Be sure and sit down before you do.

 

[RDrancher]

I haven't had a problem since cleaning up the contacts, so I'll keep my fingers crossed and hope everything keeps working.

Those prices for gauge clusters are outrageous!