Bad Ground side effects

[Soonerdad]

Would a bad ground cause there to be ZERO power to the key switch? Trying to learn something here.

 

[Mark_BX25D]

Yes, absolutely, that is quite possible.

If the battery itself is not connected to the chassis (because the ground connection is bad), then that bare metal you thought was ground isn't anything at all. You might as well have it connected to the air or your dog's tail.


A bad ground can do all kinds of strange and seemingly impossible things. A flaky or missing ground is a quick trip to the Twilight Zone.


When things get weird, check your grounds.

 

[Soonerdad]

Thanks for the info. It’s intermittent . Try several times nothing . Then suddenly there’s juice and it starts . Symbol for electrical lights up on dash and stays lit. Beginning to start running thru it all thinking dynamo is bad as something causing the light to stay on. Elect is so frustrating

 

[Mark_BX25D]

An intermittent ground is a real possibility. Remember that you can't check a connection by looking at it. Take it apart, clean everything to shiny bare metal, reassemble with a little dielectric grease. Then you know it's good.

But cables can be bad, too. Corrosion can wick up inside them under the jacket and do a number on the copper, while looking just fine. You can usually feel it by bending the cable. If it feels "crunchy" replace it. Don't be afraid to get rough with your cables to check them - if they are nearly bad, you want to break them so you know they are bad, so you can replace them.

As a test, get a known good battery jumper cable and connect your battery ground terminal to a good grounding spot on the frame. Don't be afraid to remove some paint. Then see what it does.

Electrical work requires patience and methodical troubleshooting. Don't jump from one thing to another. One thing at a time, and keep a notebook handy. Write down every step. It's just really easy to get yourself confused otherwise. I'm an engineer and I keep a notebook when doing this kind of work, or I can get lost.

 

[Henro]

Just an added thought, but remember the ground circuit starts at the negative battery terminal. Removing the clamp, cleaning, and making sure it goes back on tight is a good starting point.

 

[GreensvilleJay]

'turn key switch' as in 'start' position ?

Can easily be a bad switch,could have 10000+ cycles on it..they wear out. 'fun' is when the internal grease covers the switch contacts and randomly doesn't allow power to pass through....
How old a machine , # of hours, # of start/stop cycles...??

Typically won't be a 'bad' ground as same ground powers the starter and it won't spin without a zillion amps...

 

[Mark_BX25D]

Typically won't be a 'bad' ground as same ground powers the starter and it won't spin without a zillion amps...

Zero power TO the key switch is not due to a bad key switch.

 

[GreensvilleJay]

based on this..(more info than the OP...

... It’s intermittent . Try several times nothing . Then suddenly there’s juice and it starts .

it's typical of a bad keyswitch.

The only physical change during the 'start-no start' condition ,is the turning of the key whereas a 'bad ground' would be consistent, either low ohms or open.
It'd be nice to see the wiring diagram of the unit.

 

[BruceP]

Would a bad ground cause there to be ZERO power to the key switch? Trying to learn something here.

This is kind of a 'trick' question.

If we define:

• "Ground" to mean battery minus
• "Power" to mean Battery plus

The answer is "NO", absolutely not. It is not possible for the positive portion of the circuit to be affected by wires which only exist in the negative portion.

If you clip the minus-lead of voltmeter on the battery minus. IT IS NOT POSSIBLE for a "bad ground" to affect power arriving at the keyswitch and being measured by your meter.

=====================================

It’s intermittent . Try several times nothing . Then suddenly there’s juice and it starts . Symbol for electrical lights up on dash and stays lit.

This sounds like a flakey keyswitch. I have been able to successfully 'revive' many keyswitches using WD40. ( WD40 was invented as a Water-Displacer to fix electrical problems due to moisture-intrusion)

1. Remove the keyswitch
2. Inspect it for openings which you can insert WD40 tube and fill it up.
3. 'work' the switch back and forth 30+ times.
   1. Repeat the 'douse and work the switch' sequence several times.

This process is 'messy' so do it outside over a bucket.

I have had VERY good luck reviving keyswitches in this way.... perhaps 9 out of 10 will come back to life and work fine for many years thereafter.

 

[Mark_BX25D]

You need to spend more time in the real world and less time in a textbook. If there is no connection between the battery negative terminal and the chassis of the vehicle, a measurement of the voltage at any point in the vehicle will be zero, unless he connects his ground probe to the negative terminal of the battery, which very few people do.

A person untrained in electrical theory will report it exactly as the OP reported it. He's measuring for voltage, and sees none.

 

[GreensvilleJay]

untrained....or trained, he could have his DMM set to AC volts.....

 

[Mark_BX25D]

untrained....or trained, he could have his DMM set to AC volts.....

The question was, 'could a ground problem cause a reading of zero volts to the key switch'.

The answer is, YES, it can.


If the question had been, "what could cause a reading of zero volts", then the answer would be a lot longer.

 

[Soonerdad]

Well then let me ask the question what would cause a reading of zero Volts . Look folks, I’m just trying to learn something here not trying to cause a stink .

 

[Mark_BX25D]

Lots of things. Start with the basics. The very first thing is to make sure you are accurately describing what you are seeing. If there is no voltage going TO the keyswitch, it's a very different thing than if there is no voltage OUT of the keyswitch. I have assumed you are doing that, but if not, now's a good time to correct that. No harm,, no foul, but we need to know.

Check fuses first, of course, but I assume you have done that.

So measure at that same point you did before and put your ground probe on the negative terminal of the battery. Not the clamp, the terminal post itself. If you see voltage this time, you have a ground problem. If not, you have a supply (hot) wiring problem.

Once you know whether it's a ground or a supply problem, you can start running that down.

 

[Soonerdad]

Lots of things. Start with the basics. The very first thing is to make sure you are accurately describing what you are seeing. If there is no voltage going TO the keyswitch, it's a very different thing than if there is no voltage OUT of the keyswitch. I have assumed you are doing that, but if not, now's a good time to correct that. No harm,, no foul, but we need to know.

Check fuses first, of course, but I assume you have done that.

So measure at that same point you did before and put your ground probe on the negative terminal of the battery. Not the clamp, the terminal post itself. If you see voltage this time, you have a ground problem. If not, you have a supply (hot) wiring problem.

Once you know whether it's a ground or a supply problem, you can start running that down.

 

[Soonerdad]

last attempt here…. My tractor won’t start . Whether it’s in to the switch or out of the switch, I’m not sure what the correct explanation is . I’m not a electrical guy. I’m not an idiot either . What I do know is when I turn the damned key to start it , sometimes there’s no lights on the dash , no sound of the cutoff solenoid working or the engine cranking. Other times when I turn the key the light light up on the dash and I get a couple of cranks on the e gine and then boom, it lol goes dead again. Other times it all Works like it’s supposed to .

 

[MountainMeadows]

Any electrical troubleshooting should start at the battery. Check the battery voltage. Check your connections: remove and clean the cable ends. Follow the neg. cable to the frame or engine block. Remove and clean the frame or eng. block area and the cable end. Look closely at the cable where it enters the insulation. at both ends. If it's green and crusty replace the cables.
When all that is done take a test light or volt meter to see if you have voltage at the switch. If there's no voltage check for bad or loose connections at the fuses. If you have voltage at the switch but the dash doesn't light up and the tractor doesn't crank over it's most likely the switch.

 

[GreensvilleJay]

Your #16 post is the 'classic' bad ign switch. Really.. 'sometimes it works, sometimes it don't'. It's not just starting, it's also lights on the dash work/no work. I found a G1800 wiring diagram ( previous G1800 no start post here...) Looks like the ign switch plugs into a harness that plugs into another and maybe another......
try carefully disconnecting and reconnecting the plugs and jacks, several times, then try to start.it 'might' be a bad connection but really, my gut says it's a bad switch. It's a simple mechanical device that's only designed for xxxx number of on-offs.Add up cycles,vibration,dust,dirt, grease migration, shaving and it'll give 'random PITA start/no start/lights/no lights' problems. EVERY time you key the key, it wears out a wee bit.
if you get a good ,readable copy of the wiring diagram, you can make jumpers to 'bypass' the switch
The problem with 'testing with meter' is that if you test when the switch is 'ok', you'll assume the problem is elsewhere...go off on a wild goose chase. Now IF you test when the switch is 'bad' ,then you'll see it IS the switch. problem is the randomness of the good-nogood. If it'd just FAIL, it's be easy to SEE.
At least you don't have a 'computer' to deal with.......

 

[GreensvilleJay]

this... What I do know is when I turn the damned key to start it , sometimes there’s no lights on the dash ,

is typical of the classic bad ign switch. I grabbed the wiring diagram from a previous post here, ign sw connects to several cables. You could unplug, replug them several times BUT my gut says bad switch. Your machine is 22+ years old, the switch only designed to last xxxx cycles. Unknown how many 'turns of the key' its had. You could unplug the ign sw, jumper the connector and see if it lights up, starts, runs.
You might try the WD40 'trick' however I'd order a new switch as it's unlikely to be a wiring cable problem and everything works, when it works. Good news no dang computer to deal with !
Generally speaking 'switches' are usually the first 'electrical' thing to cause problems.

 

[Daren Todd]

You need to spend more time in the real world and less time in a textbook. If there is no connection between the battery negative terminal and the chassis of the vehicle, a measurement of the voltage at any point in the vehicle will be zero, unless he connects his ground probe to the negative terminal of the battery, which very few people do.

A person untrained in electrical theory will report it exactly as the OP reported it. He's measuring for voltage, and sees none.

Actually that's false. You need to check a circuit under a load. Even a minuscule connection can show good battery voltage. But once load is applied, power can drop off due to bad connection.

Check power going in to the switch. and then have someone cycle the key and see if power drops.

Then test the out going side of the key switch the same way. Just move the power lead to the out going terminal on the key switch while keeping the ground connected to ground.

You can test the battery cables the same way.