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cod

wire testing for an electrical moron

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Title says it all but would any of you know if there is some way to test the wires in a harness to see if they need to be replaced?  I've got a 418 and it runs great but occasionally it will not start when hot.  So I got through the "rituals" to satisfy the harness spirits (clean the ground, disconnect the plug from the ignition switch, jiggle wires, etc) and the problem goes away for months at a time.  I'm not sure if there is a resistance setting on an ohm meter that would indicate that some of the copper strands are broken although I'm not sure that is the problem.  I'm beginning to suspect that it might be easier to just run all new wires as the original are 30 years old but futzing with copper spaghetti is not my idea of a good time so any pointers/suggestions are greatly appreciated.

 

Thanks - Cod

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@cod You could use a good OHM meter and ohm each wire individually to see what the resistance is, but you would need a little electrical background to properly use the meter as well as understanding what the readings mean.

If you feel it is a wiring problem, start by checking all the connections for corrosion/tightness.

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When you say won't start hot. Are we talking it won't crank or it won't fire. If it's a cranking problem and if it's an ONAN, first thing I'd be looking at is the starter itself. 

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I agree on the ohm meter. You could clean the terminals and check connections then as you reconnect use a little dielectric grease. That will help keep good continuity. 

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17 minutes ago, squonk said:

When you say won't start hot. Are we talking it won't crank or it won't fire. If it's a cranking problem and if it's an ONAN, first thing I'd be looking at is the starter itself. 

Won't crank.  If I turn the key to the on position and jump across the solenoid, it turns over and fires up.

 

I'm heading out to garage now to do more tinkering.

 

Cod

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Posted (edited)

Check for power at the solenoid when key is in start position. If you have power you have a bad solenoid or bad connection to starter from battery. If no power the switch or wire from switch is the problem. Assuming all grounds are good and all safety switches at good and working properly.

Edited by JPWH

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If you end up replacing wires I would hit the hardware and buy a pack of adhesive wire numbers to mark them prior to replacing.... and take a lot of before pics.

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Does the row of idiot lights show a hint of what circuit is the problem? The ignition switch, pto switch and the clutch pedal (8-spd) or neutral switch (auto) is all that is involved.

 

Garry

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Just a quick update.  Went out yesterday and started cleaning all of the connections.  Removed the battery and cleaned the terminals and wires that connect to them. Disconnected all of the solenoid wires and brushed them up. Removed the ground connection and cleaned there. Removed the connector from the back of the ignition switch and cleaned each female clip and male plug (hope the wife has some spare nail files as those slots are rather tiny).  As I went I checked each wire with a ohm meter and each of them tested fine. When all of this was done I applied dielectric grease to every surface and re-assembled everything.  Needless to say the beast fired right up, it's charging the battery at around 13v and so I let it run for about 15 minutes, turned it off and it fired right up.  So for now the gremlins are placated with the ritual offering but it has exhibited this behavior in the past and perhaps when it gets real hot next with next weekends mowing...

 

Thanks for the tips and to answer Garry's question, I think the board was fried when I got it as I've never been able to resurrect it.  I had a spare board I sent to SOI and he mapped out how all the circuits ran and the parts to fix it but I haven't had the inclination to tackle that kind repair work.

I tend to solder wires in a similar fashion to how I sweat pipes and believe me it isn't pretty!  ;-)

 

Cod

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Posted (edited)
On ‎10‎/‎1‎/‎2017 at 9:10 AM, cod said:

Won't crank.  If I turn the key to the on position and jump across the solenoid, it turns over and fires up.

 

I'm heading out to garage now to do more tinkering.

 

Cod

You might want to be a little more specific when trying to describe your problems.  First post should have said something like the engine starts most of the time and when it doesn't  start right up it will if I jump the    solenoid. This would have hastened up the advice and type of advice given to solve your problem.  Just a thought.

 

 

 

 

Soldering components on a circuit boar is childs play. First, use a iron/pencil type soldering iron less than 40 watts to limit damage to circuit boards. Sometimes its easier to snip the component leads next to the component and this allows you to use a pair of needle nose plyers to remove the lead once you have the solder heated up. The best method is to use a desoldering station to 

heat the solder and remove it completely with the use of a vacuum pump.

Edited by 6bg6ga
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In addition to an ohm meter, you also can check to see if the wire can carry a load.

At work I use a sealed beam as a "test light"  to verify that a circuit is good

A circuit may show voltage with a meter, but will not carry a load.

generally if the circuit can carry enough current to run a headlight (5 to 7 amps), it is good

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10 minutes ago, edgro said:

In addition to an ohm meter, you also can check to see if the wire can carry a load.

At work I use a sealed beam as a "test light"  to verify that a circuit is good

A circuit may show voltage with a meter, but will not carry a load.

generally if the circuit can carry enough current to run a headlight (5 to 7 amps), it is good

 

 

Actually your post ties in with good connections or cleaning up connections so you can get a good connection. Many times I have seen people with cars that won't crank over and its a simple clean the connections on the battery fix. So, the battery is a really good point to start anytime you have a voltage/current problem. Sometimes connections can look great but remember it only takes a minute or two to verify the connection that you thought was good and was actually the problem.

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How is it that the connections go bad?  One would think that a clean metal surface, fastened to another clean metal surface would provide enough surface contact to prevent the build up of corrosion between the two surfaces but apparently that is not the case.  Battery terminals and the main ground connection seem to be two areas where you would have the "best" case for a large amount of surface area, but both still get corroded over time.

 

Cod

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8 minutes ago, cod said:

How is it that the connections go bad?  One would think that a clean metal surface, fastened to another clean metal surface would provide enough surface contact to prevent the build up of corrosion between the two surfaces but apparently that is not the case.  Battery terminals and the main ground connection seem to be two areas where you would have the "best" case for a large amount of surface area, but both still get corroded over time.

 

Cod

 

 

Good question.  The acid fumes are generally associated with battery terminal corrosion. The sealed newer batteries don't have quite the problem as the older batteries with the large cell caps. Having said this there still isn't a battery that is going to be free of corrosion therefore normal maintenance procedures should be followed. In other words preventative maintenance should be used. There is no absolute coating one can use in an attempt to get away from corrosion so the best thing is keep it clean as you would your body and the problem won't come up again.

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Also note a bad ground in a circuit will cause it to seek a ground from somewhere else, which may be back through another circuit.

This can cause strange behavior when there are multiple circuits that are sharing a common ground that has higher than normal resistance.

Just as a for instance, an 1157 light bulb has 2 elements that share a common ground.

If the ground is bad, it will seek a ground back through the other bulb element.

This can be a common problem on trailer lights that work, but are dim, or maybe don't blink properly

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On ‎10‎/‎1‎/‎2017 at 10:40 AM, Dan693 said:

If you end up replacing wires I would hit the hardware and buy a pack of adhesive wire numbers to mark them prior to replacing.... and take a lot of before pics.

 

Good point and I'm going to add to it. In addition to using either an adhesive label or wire markers I highly recommend using clear heat shrink tubing over the label marker. This way in 10 years and your tracing something out its a simple matter of wiping off the dust and exposing a label that can be read still.

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