Ghost voltage confuses my diagnoses

jakesnake66

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Mower won't turn over. Battery is good.

I have a 10-yr-old Husqvarna ZT, just replaced starter motor 2 years ago. Turning key causes solenoid to click, but nothing more. Voltage on battery side of solenoid is good (right at 12v). Voltage at end of starter side cable (tested disconnected from starter lug) is good (11.5v). So, my first reaction was that my 2-year-old starter is bad. Very disappointing to get only one full season out of it, but such is life....

But here's the thing: With mower key turned to OFF I'm getting 5.5v on the starter side of the solenoid, and I cannot find a direct answer to what that means. I always thought a solenoid was open/closed, period, with closed meaning no voltage passing through. But with ignition OFF, key out, I've confirmed the reading several times.

Bad solenoid? And since I'm getting 11.5v to the starter with key turned ON, does that indicate that perhaps the defective solenoid (if indeed it's defective) ruined my starter by supplying power constantly?

Sincerely appreciate any feedback. Our yard is approaching the "nobody lives here" stage, which puts my wife in the "you're not going to live here" stage. So....help!
 

EngineMan

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Mower won't turn over. Battery is good.

I have a 10-yr-old Husqvarna ZT, just replaced starter motor 2 years ago. Turning key causes solenoid to click, but nothing more. Voltage on battery side of solenoid is good (right at 12v). Voltage at end of starter side cable (tested disconnected from starter lug) is good (11.5v). So, my first reaction was that my 2-year-old starter is bad. Very disappointing to get only one full season out of it, but such is life....

But here's the thing: With mower key turned to OFF I'm getting 5.5v on the starter side of the solenoid, and I cannot find a direct answer to what that means. I always thought a solenoid was open/closed, period, with closed meaning no voltage passing through. But with ignition OFF, key out, I've confirmed the reading several times.

Bad solenoid? And since I'm getting 11.5v to the starter with key turned ON, does that indicate that perhaps the defective solenoid (if indeed it's defective) ruined my starter by supplying power constantly?

Sincerely appreciate any feedback. Our yard is approaching the "nobody lives here" stage, which puts my wife in the "you're not going to live here" stage. So....help!

Could be a few things that are bad, 1 there maybe a diode gone bad, if there is one in the wiring, we need to know your model number to look into a wiring diagram, 2 the rectifier/regulator bad, 3 bad wiring somewhere, 4 bad key switch, you should have 12.5 volts at the battery and the same on both sides of the solenoid, when the key is NOT turned to start the contact inside the solenoid is open and not us you say "closed". find the wire that has the 5.5volts on the solenoid take it off and then see if you still have the volts on that wire and then see where it goes to (coming from key switch) if you don't have any volts on the wire then you have a bad solenoid so replace it.
 

jakesnake66

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Could be a few things that are bad, 1 there maybe a diode gone bad, if there is one in the wiring, we need to know your model number to look into a wiring diagram, 2 the rectifier/regulator bad, 3 bad wiring somewhere, 4 bad key switch, you should have 12.5 volts at the battery and the same on both sides of the solenoid, when the key is NOT turned to start the contact inside the solenoid is open and not us you say "closed". find the wire that has the 5.5volts on the solenoid take it off and then see if you still have the volts on that wire and then see where it goes to (coming from key switch) if you don't have any volts on the wire then you have a bad solenoid so replace it.

Thank you EngineMan. Your reply is sincerely appreciated. Some more info:

The mower is RZ5424, Kohler motor. About two weeks ago I cranked the mower just to move it to the carport from the back shed. It wouldn't start, turned over very slowly a couple times. So I concluded the battery had drained over Winter, so I jumped it off with my truck. I know it's not ideal to do that, but a friend had borrowed my battery charger and I got impatient. The mower fired right up, and I drove it to the carport. It sat there two weeks before it failed to start Sunday.

The part of your reply that confuses me is where you say I should have the same voltage on both sides of the solenoid, but then you go on to imply that something else is supplying that 5.5v. If I have 12v at the battery and on the battery-side lug of the solenoid and, as you say, the voltage on both sides of the solenoid should be the same, then why would there ever be 5.5v (or any other value different from the 12v) on the starter side?

I'm sure the communication breakdown is my fault. I'm an IT guy, with a good bit of low voltage training, but I almost never work on engines of any kind.
 

bertsmobile1

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Nov 29, 2014
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Mower won't turn over. Battery is good.

I have a 10-yr-old Husqvarna ZT, just replaced starter motor 2 years ago. Turning key causes solenoid to click, but nothing more. Voltage on battery side of solenoid is good (right at 12v). Voltage at end of starter side cable (tested disconnected from starter lug) is good (11.5v). So, my first reaction was that my 2-year-old starter is bad. Very disappointing to get only one full season out of it, but such is life....

But here's the thing: With mower key turned to OFF I'm getting 5.5v on the starter side of the solenoid, and I cannot find a direct answer to what that means. I always thought a solenoid was open/closed, period, with closed meaning no voltage passing through. But with ignition OFF, key out, I've confirmed the reading several times.

Bad solenoid? And since I'm getting 11.5v to the starter with key turned ON, does that indicate that perhaps the defective solenoid (if indeed it's defective) ruined my starter by supplying power constantly?

Sincerely appreciate any feedback. Our yard is approaching the "nobody lives here" stage, which puts my wife in the "you're not going to live here" stage. So....help!

You are correct .
The solenoid is nothing more than a big switch and has 2 states on & off or volts and no volts if you like.
So yes the solenoid is defective and needs to be replaced or cleaned if the leakage is along the oily dusty surface, but a quick clean up will sort that.
While you are there check the trigger wire(s) at the base of the solenoid.
If there is only one it should read battery voltage in the start position and 0 in the run position, if not then you have a problem in the wiring
If you have 2 then one should respond as above and the other will be either ground all the time or open circuit and go to ground when the ignition switch is in the S position.

A lot of ZTRs use a relay to trigger the solenoid, it always amuses me a relay to control a relay, and the ignition relays do go bad.
 

jakesnake66

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To update this:

My problem turned out to be a bad solenoid.
 
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