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Briggs Stratton 19.5 HP on John Deere LA115, bout 12 yrs old maybe Model 31P677 Type 0132B1

Long story short. A few weeks ago I replaced the head gasket. All smooth except dead battery after. Would only start with a jump. Runs great. I had left the key in it the previous night at 22 deg so I assumed dead battery. I bought a new battery and starts right up. After 2 weeks sitting battery is dead again, starts great with a jump.

So I assume parasitic drain. I get out the test light, disconnect the ground battery cable. I connect the test light to the battery post, touch the cable, no light. I pull out the multimeter and test the battery shows 12.5v. I touch the starter cable connection 1.9v I backtrack to this litttle electrical box (pic) and get 1.9v coming out, but 12.5v going in. The electrical box has large hot wire in and large hot wire out, and two small wires connected.

I test for continuity on the two small connections and get 005. I test for continuity on the two big connections and get 1.

Questions.

Should I see 12v at the starter connection?
What is this electrical box?
Did I test continuity correctly and see correct numbers or does the 1 reading show the box is bad?

Any other help appreciated. Thanks

That's your starter solenoid, It's a "heavy duty" electromagnet switch, it uses a 12v low current signal from the ignition switch, to make contact between the big positive leads to the starter.
One of the smaller wires is a ground wire and the other is positive, one of them runs through the safety switches of the mower to prevent starting when the blades are engaged or seat is not occupied.
Test for 12v on the smaller wires, one of them should have 12v with the key in the start position, and do it with the parking brake engaged, to prevent a safety switch from messing up the test. Or have someone sit in the seat and turn the key to start while test for voltage. i'd recommend removing the spark plug wire from the spark plug while doing this to prevent any accidents.
I'm pretty sure that the solenoid is your culprit as my cub had that same problem quite a few years ago, replaced it and it's been fine ever since.

i'm not seeing a 115A tractor, but i do see a LA115
A john deere AUC15932 solenoid should get you up and going, This Stens solenoid will do good as well, https://www.amazon.com/Stens-435-151-Starter-Solenoid/dp/B005LA9UX2/ref=sr_1_3?crid=3J8RNFI22PRVK&keywords=AUC15932&qid=1648568084&s=industrial&sprefix=auc15932,industrial,110&sr=1-3

If you want to someone with more knowledge and experience than me should be along shortly and may give you a better answer.

The small wires on the bottom should be battery voltage and ground
One or both should be switched so you get 12V & ground which trips the switch to connect the heavy wires to crank the engine when the key is in the start position.

Scrubcadet10 said:

That's your starter solenoid, It's a "heavy duty" electromagnet switch, it uses a 12v low current signal from the ignition switch, to make contact between the big positive leads to the starter.
One of the smaller wires is a ground wire and the other is positive, one of them runs through the safety switches of the mower to prevent starting when the blades are engaged or seat is not occupied.
Test for 12v on the smaller wires, one of them should have 12v with the key in the start position, and do it with the parking brake engaged, to prevent a safety switch from messing up the test. Or have someone sit in the seat and turn the key to start while test for voltage. i'd recommend removing the spark plug wire from the spark plug while doing this to prevent any accidents.
I'm pretty sure that the solenoid is your culprit as my cub had that same problem quite a few years ago, replaced it and it's been fine ever since.

i'm not seeing a 115A tractor, but i do see a LA115
A john deere AUC15932 solenoid should get you up and going, This Stens solenoid will do good as well, https://www.amazon.com/Stens-435-151-Starter-Solenoid/dp/B005LA9UX2/ref=sr_1_3?crid=3J8RNFI22PRVK&keywords=AUC15932&qid=1648568084&s=industrial&sprefix=auc15932,industrial,110&sr=1-3

If you want to someone with more knowledge and experience than me should be along shortly and may give you a better answer.

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Awesome thank you. Yes my mistake it is a LA115.

bertsmobile1 said:

The small wires on the bottom should be battery voltage and ground
One or both should be switched so you get 12V & ground which trips the switch to connect the heavy wires to crank the engine when the key is in the start position.

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Do you know if I should see 12v at the starter connection?

Yes, anywhere there is a hot wire, you should have 12v. or Whatever voltage the battery is at.

Scrubcadet10 said:

Yes, anywhere there is a hot wire, you should have 12v. or Whatever voltage the battery is at.

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Thanks

shinkle said:

Do you know if I should see 12v at the starter connection?

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Only when the solenoid is tripped, activated. The solenoid is basically just a relay with high current contacts for the starter.

StarTech said:

Only when the solenoid is tripped, activated. The solenoid is basically just a relay with high current contacts for the starter.

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I'm seeing 12.4v at the battery and on the post going into the solenoid. 9.4v on the post coming out of solenoid and at the starter, both with the key turned on.

shinkle said:

I'm seeing 12.4v at the battery and on the post going into the solenoid. 9.4v on the post coming out of solenoid and at the starter, both with the key turned on.

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Then you have a massive voltage drop either the positive or negative electrical path. Usually caused by bad connections. Using voltage drop tests test bewteen the positive battery post and the positive battery terminal on the starter solenoid with the key held in the start position. it should well under 1V and as close to sero as it can get. It done the same for negative path from the battery negative terminal to ground right at the starter case. From you start backing up to which battery post you are using to test until the voltage drop no longer appears. Where the voltage return is good and anything after that is suspect.

StarTech said:

Then you have a massive voltage drop either the positive or negative electrical path. Usually caused by bad connections. Using voltage drop tests test bewteen the positive battery post and the positive battery terminal on the starter solenoid with the key held in the start position. it should well under 1V and as close to sero as it can get. It done the same for negative path from the battery negative terminal to ground right at the starter case. From you start backing up to which battery post you are using to test until the voltage drop no longer appears. Where the voltage return is good and anything after that is suspect.

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Do you think the drop is in the solenoid itself? or on the solenoid connections.. since he as 12V at the + post on the solenoid, and 9V coming out?

Scrubcadet10 said:

Do you think the drop is in the solenoid itself? or on the solenoid connections.. since he as 12V at the + post on the solenoid, and 9V coming out?

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It appears that was the case. I put a new solenoid on and it seems to have fixed it. Starts right up. The only thing I was unsure of is my original solenoid has the battery/starter posts vertical and my replacement has them horizontal. So I wasn't sure exactly which post to connect the battery and which to connect the starter, it may not matter since its basically just completing the connection between posts.

Thanks for all your help, maybe this will help someone else down the road.

You are correct, it really doesn’t matter.

Rivets said:

You are correct, it really doesn’t matter.

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^^^^^^