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No 12v power to PTO, lights, hour meter.

#1

G

gobucs1

I just picked up a used YTH24K48 that I have no history about except it quit running while cutting and the guy parked it. No fuse was blown or wiring altered before I got the mower he said.

When I got it the battery was dead and it recharged and fired up. PTO does not engage but switch has continuity through it as it supposed to when up or down.

Testing based off the A1 spot off the ignition I would this this should be 12v positive output but it is 12v ground tested with continuity and test light. Blue wire that goes to spot A on the PTO switch.

When I run a new direct wire off of positive battery in place of the blue wire the PTO engages.

Any help to get this mower correct will be great.

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#2

StarTech

StarTech

Then most likely the ignition switch is bad or there is no 12v on the B terminal of the switch. Can also be cause by a bad wire terminal.at the ignition; either B or A1. Even can be terminal any where along the circuit path. I even one late last Summer where the battery cable terminal was bad internally that read voltage off load but as soon there was a load the voltage would drop out.

Test lights can give false ground readings as well continuity tests as there other components in the circuit like the fuel solenoid and hour meter that lowers the circuit overall resistance to less than 5 ohms.


#3

B

Born2Mow

StarTech said:
Test lights can give false ground readings as well continuity tests as there other components in the circuit like the fuel solenoid and hour meter that lowers the circuit overall resistance to less than 5 ohms.
Click to expand...
Yes and No. I'm not disagreeing, but I feel the need to give a more complete explanation. The test light is a tool, and like any other you need to be careful how you use it and what conclusions you draw.

Most people connect a test lamp to a good grounding point, say Neg terminal of the battery. But with that setup you can ONLY test for the DELIVERY of 12V power.... which is exactly 1/2 of the circuit. Obviously, the circuit is not working because any break any place in the circuit prevents the device from working.

The other half of the circuit, the RETURN of power back to the battery, is just as necessary as power DELIVERY. Therefore you may need to connect your test lamp lead to the Pos battery terminal when chasing "ground" problems.

But your second point is extremely valid. The presence of 12V as indicated by a test lamp does not indicate the presence of enough current carrying capability to operate high current items like starters and electric clutches.

Just my 2 cents.


#4

G

gobucs1

StarTech said:
Then most likely the ignition switch is bad or there is no 12v on the B terminal of the switch. Can also be cause by a bad wire terminal.at the ignition; either B or A1. Even can be terminal any where along the circuit path. I even one late last Summer where the battery cable terminal was bad internally that read voltage off load but as soon there was a load the voltage would drop out.

Test lights can give false ground readings as well continuity tests as there other components in the circuit like the fuel solenoid and hour meter that lowers the circuit overall resistance to less than 5 ohms.
Click to expand...

The ignition switch does start the mower but could be bad as well I suppose. I do not know much about them.

There is 12v positive on the B terminal of the ignition switch. I just tested it from harness to the negative post.

20210201_112410.jpgJust pulled the ignition off of the front and A1 looks slightly melted so I am guessing the switch is bad but still starts the mower.


#5

StarTech

StarTech

A1 terminal on the switch show signs of extreme overheating due to high draw so can be the problem. Using an Ohm meter test the PTO clutch coil resistance it should be above 1.7 ohms. Anything under this is a partially shorted clutch coil. I have seen these to pull up to 20 amps and still work but they normally pull under 7 amps with around 3-5 amps being more normal. The switch overheating can also been cause a loose F56 wire terminal where the spring back is broken.


#6

StarTech

StarTech

Born2Mow said:
Yes and No. I'm not disagreeing, but I feel the need to give a more complete explanation. The test light is a tool, and like any other you need to be careful how you use it and what conclusions you draw.

Most people connect a test lamp to a good grounding point, say Neg terminal of the battery. But with that setup you can ONLY test for the DELIVERY of 12V power.... which is exactly 1/2 of the circuit. Obviously, the circuit is not working because any break any place in the circuit prevents the device from working.

The other half of the circuit, the RETURN of power back to the battery, is just as necessary as power DELIVERY. Therefore you may need to connect your test lamp lead to the Pos battery terminal when chasing "ground" problems.

But your second point is extremely valid. The presence of 12V as indicated by a test lamp does not indicate the presence of enough current carrying capability to operate high current items like starters and electric clutches.

Just my 2 cents.
Click to expand...
Maybe I just use to my Snap-on test light that indicates both voltage and grounds. Plus I got 40+yrs of working with electrical and electronics.


#7

G

gobucs1

StarTech said:
A1 terminal on the switch show signs of extreme overheating due to high draw so can be the problem. Using an Ohm meter test the PTO clutch coil resistance it should be above 1.7 ohms. Anything under this is a partially shorted clutch coil. I have seen these to pull up to 20 amps and still work but they normally pull under 7 amps with around 3-5 amps being more normal. The switch overheating can also been cause a loose F56 wire terminal where the spring back is broken.
Click to expand...

The ohms was 3.7 with meter showing .4 as a baseline connecting positive to negative. Clutch does work and turn on but I first removed it and sprayed it heavily with PB blaster first before testing 12v direct to battery since it seemed to spin tough to me by hand.


#8

B

Born2Mow

StarTech said:
A1 terminal on the switch show signs of extreme overheating due to high draw so can be the problem.
Click to expand...
Looks like it to me too. And if you pop the back off the switch you may see a burned contact inside on that pole.

This is one of those cases where a Test Lamp will lie to the user. The burned up switch contact can carry 12V at a current level high enough to light up a 3W Test Lamp bulb, but not nearly enough to operate a high current clutch.

Hope this helps.


#9

B

Born2Mow

StarTech said:
Maybe I just use to my Snap-on test light that indicates both voltage and grounds.
Click to expand...
You young guys get all the good tools !! :ROFLMAO:

My Snap-On test lamp bought in 1971 only does the basic ON/OFF trick.


#10

B

bertsmobile1

A few years back some veteran riding pals were having a coffee stop at my yard
When they went into the garage they nearly wet themselves with excitement when they saw my test lamp.
No I have no idea when or where I got it from but apparently it was a very rare trouble lamp from the tank console of a 1922 motorcycle.
After they decided who should have it I sacrificed an olf bed lamp to do the same job with a 32 V DC globe borrowed fro a train carriage.


#11

StarTech

StarTech

Born2Mow said:
You young guys get all the good tools !! :ROFLMAO:

My Snap-On test lamp bought in 1971 only does the basic ON/OFF trick.
Click to expand...
I usually just one like that and the fancy one just to show off. Most times when I looking for agrounded circuit I just connect a test light to the positive post. A lot easier of see a bright light than those leds.


#12

G

gobucs1

Just to give an update. I installed a new ignition switch and it fixed the problem. Thank you!


#13

B

Born2Mow

No Charge !
Come back and see us again soon.


#14

StarTech

StarTech

Hopefully you changed the wire terminal also on that ignition switch terminal or you be back at changing the switch again soon.


#15

G

gobucs1

StarTech said:
Hopefully you changed the wire terminal also on that ignition switch terminal or you be back at changing the switch again soon.
Click to expand...
The terminal in the harness looked decent. I will pull apart soon (it is below freezing the next few days) and see. Thank you for the further input. I only started the mower and saw it was fixed and have not ran it yet.


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