Volt meter drop with lights on.

[Posimoto 5]

I have a reading of 14.2v lights off and 14.3v with lights on. Charging systems seems to be working fine but when the lights are on the gauge reads under 12v (yellow).

Is this a common thing or is it possible there

[Save Old Iron 1,563]

Is this the 520 or the 212 ?

[Posimoto 5]

520, I'll remove the 212 from my sig (sold)

Side note: lights off gauge read correctly.

[Save Old Iron 1,563]

14.2v lights off and 14.3v with lights on

but when the lights are on the gauge reads under 12v (yellow).

This is a little confusing.

Where are you measuring the 14.2 and 14.3 volts ?

and with what ? multimeter ?

where? at the battery or elsewhere ?

but as a first round of troubleshooting without knowing the above details, try this.

Measure the voltage across the tractor voltmeter with a multimeter. Read right across the tractor voltmeter terminals.

If the multimeter reads 14.something and the tractor voltmeter reads 12 something, the voltmeter is defective.

If the multimeter and the tractor voltmeter read the same, we have a very high resistance path to the tractor voltmeter leads,

[Posimoto 5]

At the battery using a multimeter.

I

[Posimoto 5]

Results using a multimeter

At battery

Idle - lights off -13.9 / lights on 12.4

Half throttle - lights off -14.2 / lights on 14.3

At tractor voltmeter terminals

Idle - lights off 13.3 / lights on 10.

Half throttle - lights off 13.3 / lights on 11.1

[Save Old Iron 1,563]

Good info. Thanks

At battery

Idle - lights off -13.9 / lights on 12.4

Half throttle - lights off -14.2 / lights on 14.3

13.9 at idle = minimal charge current to battery at idle - not really a problem and expected

12.4 at idle is also expected - when you turn on the lights, you draw about 7 - 8 amps from the battery. Since the charge circuit is not supplying that much current at idle, the battery is now powering the 8 amps (but able to support this with a 12.4 voltage). This tells me your battery is probably in decent condition.

At tractor voltmeter terminals

Idle - lights off 13.3 / lights on 10.

Half throttle - lights off 13.3 / lights on 11.1

interesting ..... 14.3 lights on half throttle and 11.1 volts at the gauge wiring. That tells me you have a resistance in the wiring that drops (14.3 - 11.1) = 3.2 volts across some resistance in the wiring circuit.

Let's play with Ohms law a little here.

E = I x R

but we what to find resistance when we know voltage drop (3.2 volts) and we know the current I to be about 8 amps from the headlight load.

so

3.2 = 8amps X Resistance (ohms)

divide each side of the equation by 8

3.2 / 8 = 8R

0.4 = R

so we have a half ohm or so resistance somewhere in the wiring.

Look for corrosion on any terminals in the 9 pin white engine connector which supplies power to the charger circuit.

I'll check out the wiring diagram for a 520 tonight and stick my head under the dash of my 520 in the corner of the garage to see if anything jumps out at me. And given the time the tractor has been sitting there, something is bound to jump out at me !! LOL

I'll be happy to hang in there with you to find the cause, but I'm sure we are looking at some type of terminal corrosion in the wiring harness.

[mavfreak 11]

were do you get your pictures! :)

[WH nut 553]

You can always do a voltage drop test along all the wires and pin point which one it is real quick

[Save Old Iron 1,563]

Hook up a voltmeter to read 12 volts. Turn on the lights. Tractor is NOT running.

Negative lead to battery + terminal and use the red + meter lead to measure points 1 thru 4.

Start at point 1 which is the 9 pin white "engine" connector. Measure the "red" wire coming up from the solenoid assembly. If the resistance is present in the 9 pin connector, you will see your 2 - 3 volt drop across the 9 pin connector at point 1.

If voltage drop is small (0.something), move on to point #2 - the 25 amp fuse holder and look for the 2 - 3 volt drop.

Then go to point 3 - 4 etc. until you see the meter read the 2 to 3 volt drop.

The problem will be in the component at which you see the voltage drop.

If you see several tenths of a volt dropped at each connection you check, it is POSSIBLE you have several corroded connections all "adding up" to one distributed voltage drop.

Chances are you will see a drastic jump in voltage drop across the fuse holders or the 9 pin molex connection. I'll put my lunch money on the fuse holders.

Let us know what happens.

[Posimoto 5]

First, I would like to thank you for your detailed post very helpful.

Measure the "red" wire coming up from the solenoid assembly.

It appears I don't have a red wire coming from the solenoid.

One post has 3 wires

1 - orange to starter relay

1 - black to 30amp fuse (14AWG)

1 - black to harness (lighter gauge)

With lights on I probed the black wire that leads up to the harness with a reading of 6.8

Not sure it this is the correct wire?

The white wire at the 9 pin connector is 3.5

[Save Old Iron 1,563]

Posi,

you are welcome. It is my pleasure to help

the previous diagram was not my best effort - some of the meter leads blocked off the "RED" designation on the 9 pin connection.

If you have not downloaded the Toro Demystification guide, it would be very helpful if you did. Use the Search function on this site to get a link to the Toro.com site.

One issue with the guide is that it calls out wire colors that sometimes are incorrect.

In the case of the "ENGINE SIDE" of the 9 pin connector, most wires are all black. So we will have to trace the wires back to their origin and troubleshoot by the FUNCTION of the wire and not the COLOR.

Find the wire labeled "RED" in the following diagram. It should lead thru the 9 pin back to the solenoid stud on the engine.

Tractor off - lights on - measure voltage drop from the solenoid stud to the "RED WIRE" side of the pin 9 on the 9pin connector.

There should be very little voltage drop measured here - maybe less than .3 volts or so. This # is not in stone, but I would not expect any significant drop.

If you do see .5 or above voltage drop, the connection at pin 9 is corroded or the the wire terminal to the solenoid stud could benefit from cleaning. It is possible the wire is corroded within each metal terminal crimp.

more detail to follow

[Save Old Iron 1,563]

meter leads here will check the voltage drop across the 20 amp fuse holder and fuse

here we check the voltage drop across the ignition switch thru the accessories terminal

and then finally thru to the light switch - this is where the pink wires leading to the voltmeter are actually measuring the voltage at. Any difference in the battery voltage and the voltmeter indication has to be due to a voltage drop between this "pink dot" on the schematic and the +12 wiring to the solenoid stud.

A little more ohm's law,

wattage = current x voltage

wattage = 7amps x 3 volts (voltage drop across the resistance we are trying to find)

wattage = 21 watts.

That's fairly significant. Like the heat produced from a tailight bulb. You might even be able to use your fingers to "feel" for what feels warm. The fuse holders or wiring connections may be getting warm / hot. Certainly an infrared thermometer should be able to pinpoint this localized heating.

You can never have enough tools to help the diagnosis !!

[Posimoto 5]

Thanks Chuck for the diagrams, advice, and the lead to the Demystification guide. I've been busy and should have some time later in the week to test further. I will post at that time. Again, thanks.

[Save Old Iron 1,563]

Hang in there with us on this one.

Verrrrry interesting.

[mavfreak 11]

I always learn something everyday espeicaly when I read your post SOI! :)

[Posimoto 5]

Measuring from the solenoid post to the red wire side of the 9 pin connector.

Lights off, .01

Lights on, .14

I cleaned the 4 terminal rings on the post and re-checked

Lights off, .01

Lights on, .14

I cleaned the connector with a small file and rechecked

Lights off, .01

Lights on, .12

There doesn

[Save Old Iron 1,563]

Posi,

the key here no real change in voltage drop when lights are on or off.

Remember - we are looking for a 2 volt drop, not a 0.02 difference.

The 9 pin connection for power to tractor looks good (somewhat surprising, but OK)

Let's move on to the next check - 9 pin to ignition switch - which measures voltage drop across the 20 amp fuse.

Do the same measurements - lights off - lights on

When we see a 2 volt change somewhere when lights are on / off - then we found the culprit.

[Posimoto 5]

Across the 20 amp fuse holder and fuse

Lights off - .09

Lights on - 1.25

Ignition switch through the accessories terminal

Lights off - .14

Lights on - 1.50

Through to the light switch

Lights off - .31

Lights on - 2.70

[Posimoto 5]

I seem to have a faulty light switch. The male prong is a bit loose when I push in the plug (pink wire) the lights go out when released the light go on. The other prong (green wire) has a bit of play but the lights stay on while the plug is moved.

I cleaned the switch

Lights off - .14

Lights on - 2.20

[Save Old Iron 1,563]

Across the 20 amp fuse holder and fuse

Lights off

[Posimoto 5]

be prepared to replace the ignition switch (due to loose connector) or possibly the push on terminal on the pink wiring.

I seem to have a faulty light switch. The male prong is a bit loose when I push in the plug (pink wire) the lights go out

It's the light switch that has the loose connector.

Thanks for the help I'll keep you posted.

[Save Old Iron 1,563]

Just as a quick reminder, to replace the 25 amp fuse holder and fuse,

purchase a 30amp version of the fuse holder (heavier contacts and wiring than the 20 amp version).

It is just a little beefier and will last a bit longer.

A hooded holder will also help keep out condensation and debris.

---------------------------------------------

When you get the voltage drop across the fuse holder down to the tenths of a volt,

check the voltage drop thru the IGNITION switch also .

http://www.wheelhorseforum.com/index.php?...9256&hl=autopsy

The contacts in the ignition switch are heavy duty and should not be the source of a significant ( greater than .25v) voltage drop.

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Continue on in the same fashion with your measurements to see if the 15 amp fuse holder also may need replacement.

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The LIGHT switch should obviously be replaced but would not cause a voltage drop that would be measured by the voltmeter on your tractor.

[Posimoto 5]

Thanks,

The previous owner used duct tape as a hood on the fuse holder.

[Posimoto 5]

I cleaned the fuse holder with a file and installed a new fuse.

Before cleaning

Across the 20 amp fuse holder and fuse

Lights off - .09

Lights on - 1.25

After cleaning

Lights off - .02

Lights on - .34

Next, ignition switch through the accessories terminal

Lights off - .25

Lights on - 1.50

Removed the ignition switch and cleaned (without dismantling)

Ignition switch through the accessories terminal

Lights off - .11

Lights on - .48

I cleaned the 10 amp fuse holder and replace the fuse as well. Using some electrical tape I got the light switch working as it should.

Results

At tractor voltmeter terminals

Before

Half throttle - lights off 13.3 / lights on 11.1

After

Half throttle - lights off 14.1 / lights on 13.1

Chuck, you doubled your lunch money. Thanks for walking me through the procedure it was much appreciated. :)