Tractor runs fine, fuel gauge, etc. works. Dash warning lights do not. (L3650)

[J-H]

Kubota L3650, early '90s. Problem identified during the engine fix (previous thread here) caused by the oil cap being lost and the engine running without oil.

I've had this tractor for about 3.5 years, and the 3 dash warning lights below the gauges have NEVER worked. I didn't even know they existed until my neighbor pointed them out. The oil level warning, alternator warning, and I don't recall the 3rd one, don't ever come on.

I checked the fuse box near the front of the engine, and the fuses are fine. None of the wiring appears visibly damaged.

I have searched the internet and did not find a troubleshooting process for this. I expect I'll have to take off cover plates to get to the control panel, and then there will be something with checking to see if power is getting to the lights - but how would I trigger "Alternator not working" or "Low oil pressure" warning sensors to get current there in the first place to test?

 

[Dave_eng]

The three warming lights should come on when the key is first turned to the ON position. Then they go out.

This is to show you the bulbs are working.

Make certain you are turning the key too quickly to give the warning lights a little time to come on before hitting start.

Dave

 

[J-H]

I've left the key turned to the right but not on a few times in cold weather to give the glow plugs time to warm up. I don't know if that's even a thing in this tractor or not, but when I was having trouble starting the tractor, it was one of the suggestions.

No lights.

 

[Roadworthy]

If the fuses are good check for a ground to the dash. It may be missing or corroded.

 

[Russell King]

Since you bought it used, I would start by verifying that there are bulbs in the sockets. They often vanish when tractors go up for sale.

You can also rig batteries to get 12v and see if applying power to the wires to see if they light up then see what needs to be fixed to make them work.

Getting a schematic is a good place to start, and understanding that is next.

 

[J-H]

Shouldn't there be something connecting to the back of these light bulbs?

 

[nota4re]

You should be able to half-turn those bulb sockets and remove them. Check to see if the bulbs are there - and if they're good. (That's all part of a circuit board - you can see the traces and the wire feed looks to be that harness on the end.)

 

[bsekf]

On my m7030 the idiot lights are called "The Easy Checker" and mine don't work either. However the glow plugs, fuel gauge, temp gauge and switch work. I have a small parasitic drain and, I think, a bad battery. I hesitate to tear into it for fear of losing what I have. Would like the oil pressure light! Looks like you may have found your problem. No wires.

 

[Russell King]

No, the printed circuit is the wiring.

Corrosion seems to be a problem, perhaps use deoxit or similar product to clean the contact points.

You can probably get replacement bulb holders

 

[J-H]

The bulb sockets each have two contact points on them, and those are pretty clean. I'll try getting some Deoxit and will use it on the circuit board to see if that clears it up. It's ordered and should arrive next week.

 

[Russell King]

You can also see if there is any voltage at the wiring harness and if there is some there does the voltage get to the point on the circuit board to make the bulb glow

 

[J-H]

The circuit board looks a lot cleaner now, but still no lights. Am I just sticking the multimeter into the wiring harness and then grounding the other side onto the tractor body to check for current?
Or will my light-up "there is current here" detector work?

 

[nota4re]

Are the bulbs good? Did you check continuity across the filament with the bulb pulled out of the socket and again across the contact points with the bulb seated? Don't overlook the easy things!

 

[J-H]

Continuity checking: The setting on my multimeter where it goes "squee" if current goes through. Yeah, it's been 21 years since that "electricity and magnetism" class in college.

I have continuity on one of the 3 bulbs in their little turn-out sockets, even after spraying the contacts with deoxit. Could it be like a string of Christmas lights where none of them light up if one bulb is bad?

Guess I need to get a new set of bulbs and maybe sockets if they are cheap.

If it's the wiring harness, where do I stick my multimeter probes to test them, and how would I get the harness to send current (to light up error lights) when the tractor is already running?

 

[Russell King]

I have continuity on one of the 3 bulbs in their little turn-out sockets, even after spraying the contacts with deoxit. Could it be like a string of Christmas lights where none of them light up if one bulb is bad?
No

If it's the wiring harness, where do I stick my multimeter probes to test them, and how would I get the harness to send current (to light up error lights) when the tractor is already running?
Find the wire to the alternator warning light (it should be activated by just turning the key on). Put the meter on volts DC good for a bit above 12 volts range. Attach meter ground wire to the ground on tractor. Attach the meter positive cable to the alternator warning wire (or pin on the connector). Turn tractor key to on position and meter should be steady at around 12.5 volts (same as if directly measuring across the battery).
Same for oil pressure light.
Don’t know for third since I don’t know what it is for.

If you have a wiring diagram it will indicate the wire color and probably the pin number in the connector for these three lights. If not I can look at mine to suggest the wire color.

 

[J-H]

Thank you!
0 current on any of the contacts in the wiring harness.

At least the back of the circuit board is cleaner now.

The service manual I have for the tractor is so undetailed that it's not very useful. I guess my next step is to trace the wiring harness back to the fusebox to see if there's anything that looks hinky along the way.

 

[Russell King]

Don’t check amps (current) or ohms (resistance), check voltage at the harness pins.

Your reply says “0 current” is why I am saying to test voltage.
You could also switch to a test light to see where voltage does appear.

If you’re unsure about the meter or testing with it then switch to the test light and ask for more information on how to use it.