G1800 headlight switch trips fusible link

bstauss

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Equipment
G1800
Aug 12, 2020
15
0
1
70070
Just bought a G1800 with 1100 hours. Owner sold it as a "parts" tractor, but it runs and mows. Going through it, I noticed the headlights were not plugged into the wiring harness. With engine running, I turned on the headlight switch and it immediately killed the engine. And no power to the instrument cluster. It tripped the fusible link just past the starter in the harness. What would cause the headlight switch to do that? I did notice on the instrument cluster when I bought it that the fuel and temp gauges do not work, so maybe I need a new cluster? They are quite pricey - are there any good outlets for used parts?

Also, the dynamo is putting zero out to the battery - I get 12.5V at the battery with the engine off or running. Do I need a dynamo? Also a bit pricey, but needed if it's bad. I see a voltage regulator in the wiring harness, maybe it's bad? How can I troubleshoot which is bad? Thank you.
 

i7win7

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Equipment
BX2370, B2650 grapple, tree puller, trailer mover, 3 point hoist, mower, tiller
Feb 21, 2020
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1st thing I would fix is the electrical short that blows the master fuse. They maybe getting harder to find but get an incandescent work light and use it as the master fuse. It will limit the current flow. It may dimly glow with the head lights off. It will burn full brightness when you turn head lights on (electrical short). Wiggle/inspect wires, when short is removed test lamp (test fuse) will dim. repair wiring and replace master fuse. If tractor has a metal headlight relay, the relay maybe cause of short.
 

bstauss

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G1800
Aug 12, 2020
15
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1
70070
Great suggestion, but I'm not quite following you. How would I replace the master fuse (assuming you mean the fusible link) with an incandescent work light? Is that a 12V work light that I hard wire in place of the fusible link?
 

Dave_eng

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M7040, Nuffield 465
Oct 6, 2012
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Williamstown Ontario Canada
Dynamo is so simple it rarely fails. To test it, use a multi meter set to measure AC voltage. Disconnect two output wires and measure the voltage between these two wires with engine at full rpm.

18 to 22 volts would be good.

Regulators do fail and that may be what is why your tractor is not charging.

Dave
 

bstauss

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Equipment
G1800
Aug 12, 2020
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Ah, AC voltage. Thanks Dave. I'll do that when I get it running again. I pulled the fusible link off of it tonight (the green wire loop near the starter) and checked it with a meter. It has continuity, which is not what I was expecting. I guess next step now that I have a wiring diagram is to trace it through the harness until I find where the voltage disappears.
 

bstauss

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Equipment
G1800
Aug 12, 2020
15
0
1
70070
So, I got the G1800 running tonight. Turns out that 2 of the 3 fuses behind the deck screen were bad. I swear they looked good and had continuity when I checked them earlier. But my 12V test light doesn't lie (I only had my ohm meter earlier). I replaced all 3, turned the key and the dash lit up and the fuel gauge worked. Glow plugs worked, but the key would not turn the starter. A screwdriver across the starter terminals and it fired right up. I don't know why the key used to work the starter and now it doesn't. I let it warm up and found that the temp gauge is still not working.

And Dave - thank you! I tested the dynamo as you suggested and at full throttle it is putting out 38V AC. So, the battery not charging is downstream somewhere.

A good night's work. I can at least move the tractor now under it's own power. Pushing is really hard with no release valve on the transmission.

Thanks for all the help!
 

i7win7

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Equipment
BX2370, B2650 grapple, tree puller, trailer mover, 3 point hoist, mower, tiller
Feb 21, 2020
3,170
3,636
113
Central, IL
Glad your making progress and master fuse is OK. If anyone blows the master fuse in the future, this is why an old fashion incandescent can be a trouble shooting tool

Great suggestion, but I'm not quite following you. How would I replace the master fuse (assuming you mean the fusible link) with an incandescent work light? Is that a 12V work light that I hard wire in place of the fusible link?
yes use quick connects, alligator clips or solder wires to blown fuse (it's already junk) incadescent bulb is just a special wire that increases in resistance and limits current.
ex. 5 watt bulb -> 5watts/12volts=4.16amps
any short circuit wanting to pull over 4 amps will power test lamp at full power

For smaller fuses a low wattage marker lamp is more suitable
 
Last edited:

GreensvilleJay

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Equipment
BX23-S,57 A-C D-14,58 A-C D-14, 57 A-C D-14,tiller,cults,Millcreek 25G spreader,
Apr 2, 2019
9,679
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Greensville,Ontario,Canada
be sure to get a good, accurate wiring diagram/ schematic of your new ride !!! without it you can spend hours or daze trying to figure out why 'it doesn't work'.......
If it's a 'PDF', print off 2-3 copies. keep one on the wall, nice and clean, for reference cause the one at the tractor somehow will have grease and oil and dirt on it very soon !
 
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bstauss

New member

Equipment
G1800
Aug 12, 2020
15
0
1
70070
Working on the next issue - it appears the battery is not getting charged. I put a voltmeter on the battery with the engine running at near full throttle. The meter gradually finds it's way up to 13.6/13.7 volts. Thinking it needs to be more like 14.5, I ordered one of those cheap knockoff regulators on Amazon, plugged it in, and get the exact same voltage readings, even the gradual ramp up over 10-20 seconds to 13.7 volts. I'm not so sure it is the regulator. Thinking something else is not allowing the battery to charge. Any thoughts? Thanks for your help.
 

PoTreeBoy

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Equipment
L35 Ford 3930
Mar 24, 2020
2,344
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WestTn/NoMs
Working on the next issue - it appears the battery is not getting charged. I put a voltmeter on the battery with the engine running at near full throttle. The meter gradually finds it's way up to 13.6/13.7 volts. Thinking it needs to be more like 14.5, I ordered one of those cheap knockoff regulators on Amazon, plugged it in, and get the exact same voltage readings, even the gradual ramp up over 10-20 seconds to 13.7 volts. I'm not so sure it is the regulator. Thinking something else is not allowing the battery to charge. Any thoughts? Thanks for your help.
13.7 Sounds good. What battery voltage do you get with the engine off?
 

bstauss

New member

Equipment
G1800
Aug 12, 2020
15
0
1
70070
13.7 Sounds good. What battery voltage do you get with the engine off?
12.5 volts. I'm assuming the battery is good. It easily starts the engine and holds a charge for days and will start again then.

I have another G1800 that is putting out over 14V running and the voltmeter immediately jumps to 14.5 when connected. On this G1800, it lazily finds it's way up to 13.7.
 

PoTreeBoy

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L35 Ford 3930
Mar 24, 2020
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So we know it's charging some. Turn the lights on with engine running and see what the battery voltage is.
EDIT Your tractor has a dynamo and rectifier. These are pretty much go/no go and yours seems to be go. You could clean connections if you have time to kill.
 
Last edited:

bstauss

New member

Equipment
G1800
Aug 12, 2020
15
0
1
70070
So we know it's charging some. Turn the lights on with engine running and see what the battery voltage is.
EDIT Your tractor has a dynamo and rectifier. These are pretty much go/no go and yours seems to be go. You could clean connections if you have time to kill.
Well, the headlights are a problem. They were disconnected when I got the tractor. They are still disconnected. If I turn on the headlight switch (no headlights connected in the harness), it blows the 20 amp fuse (I think it's the 20) and the engine immediately shuts down.
 

lugbolt

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ZG127S-54
Oct 15, 2015
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bad ground is one likely issue. These old things were very well known (and occasionally hated) for their electrical issues, bad ground was one of many.

there are several harness connections. 2 or 3 under the dash, one up under the steering pedestal, several up by the engine, etc. They are all critical. Take each one apart, clean all of the pins, apply grease and reassemble. After assembling all of them do a drop test across the individual wires in the connectors. You can do it before you start too to know which one is giving you fits. You do it with a load on the electrical system, whether it be light bulbs or whatever. I usually just turn the key on & check all of them, but the ones that feed the charging system you have to do with the engine running--and you'll have to be real careful there. Remember the dynamo puts out AC voltage and it can zap you so be mindful of that, AND rotating engine parts.
 

bstauss

New member

Equipment
G1800
Aug 12, 2020
15
0
1
70070
Continuing to make progress. I'm not sure what's going on with the regulator and charging the battery. As I noted, with engine at WOT, you can watch the volts gradually build up with a volt meter - 13.4, 13.5, it climbs to about 14.5 over the course of a minute and stops at 14.5. So it is charging, but takes a while to get there. If I take the voltmeter off the battery and then put it back on, it jumps right to 14.5V. Since the cheapo Amazon regulator did the same thing, I don't think it is the regulator. I'm sure the new dynamo belt helped - the old one was completely worn and loose. Not sure where to look next. It's charging for now, and I mowed with it today, stopping and starting it several times with no issues.

Speaking of starting, I found a connector behind the dash that was pulled apart. A red/yellow wire. I swear the wiring diagram says that wire is for the headlights (makes sense given my head lights issue). So I plugged it back in, and started it up - and the key worked the starter for the first time - no screwdriver needed. Turned on the headlights and it immediately popped the 10amp fuse and killed the engine. No change there. When I mowed today, it started every time with the key. So, that was a success with the starter. Slowly working through the issues. The headlights have me baffled. But, I have yet to go through the wiring harness and grounds completely.
 

Russell King

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Equipment
L185F, Modern Ag Competitor 4’ shredder, Rhino tiller, rear dirt scoop
Jun 17, 2012
4,607
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113
Austin, Texas
On my tractor headlight wiring is brown for one beam (low?) and yellow for the other beam (high?). Same color runs all the way to headlights so you can verify the colors at the headlights.