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Hello, and thanks in advance for your help. For context, we are young/new homeowners and neither are mechanically inclined. We have been doing our best to learn as we go and have replaced blades, belts, and the battery on this mower since we purchased it second hand. However, we are far from being able to decipher parts diagrams easily and there's a lot of basic terms we don't understand whenever we try to read through trouble-shooting guides. I'd appreciate any clarity you guys can give me. We have an MTD mower, possible model numbers: 13AF673G000 or 13AF675G062 or 13BF675G062. We don't know the exact model number because when we bought it, the usual sticker under the seat was missing. Possibly built 04/24/02. To find parts list/maintenance/operators manuals, we go here and can find what seems to be the appropriate manuals under model number "13Af673g000".

The problem today: the mower won't start at all, we're not even getting a clicking sound or an engine-turnover sound when we turn the key. Voltage across the two battery terminals does measure 12+. This battery was new in 2020 and I don't think we've had issues with it since we installed it. This is the first attempt to start it for the season. Over the winter it was kept in a garage. The mower has gas, a fresh oil change, and the spark plug is fully attached. And the gas line is open.

The black battery post appears melted (see attached photos)? Could this be causing an inconsistent connection and thus preventing the motor from starting? I assume we need to replace the battery, but why would it have melted - e.g. what is the underlying problem, and I assume it would be something we would need to fix other than just replacing the battery? We did remove the battery today and the wires (red and black) that connect to it seem fine, don't seem to have breaks in their insulation, etc. At least, not until they run internally into the machine.

I believe the battery was purchased at Lowe's, in 2020. Brand, Magna Power, part no U1L-150. CCA@0 degrees: 150. CCA@ 37 degrees: 175.

Thanks much in advance!

Welcome
Could you tell us the make of engine fitted ?
If you do not know it then take a photo and post it .
Note most phone plhots will ned to be resized in a photo editing app
Make it 12 " along the longest side, set the resolution to 72 dpi and the file type jpg

You are correct, the batttery post has melted .
When high current ( amps ) is drawn through a conductor it generates heat
If you have plug in heater you would have noticed the power cord gets quite hot
A battery can be made to work as an arc welder
The electricity does not care weather you have a welding rod on the end or a starter motor
A starter motor is a dead short circuit across the battery terminals

This is one of the reasons why owners manuals tell you only to crank for 30 seconds continious then wait for a couple of minutes.
When wires get hot their resistance to passing high amps increases so you have a self feeding loop
The wires get hotter and draw even more amps which makes the wires hotter so it draws more amps which makes the wires hotter etc etc etc
And this includes the wires in the starter motor as well

Resistance to electric flow generates heat so dirty or corroded terminals generates heat
A faulty starter motor generates a lot more heat than a good one .

Loose terminals or a broken wire will cause sparks to happen
The only difference between a sparky joint and an electric welded is the amps

And the problem might not be at the battery terminal
usually a dag rusty ground connection at the mower end or a bad cable itself will be the problem
However it is just a case that the lead treminal on the end of the battery has the lowest melting point ( around 300 deg C )

SO there is your background now how to fix it
remove the battery cables ( cable = very thick wire ) one at a time at both ends
Polish them shinny check that the wire is tight in the terminal with no corrosion
If the end are grotty with lots of corrosion ( green / blue granules ) if more than 1/4 of the wires are broken away, replace the cables
I usually get automotive ones because they are cheaper than mower ones .
I don't know about USA shops but down here most ground cables have a flat bolt on terminal at both ends where as power cables alway s have a rouns terminal on one end.
When I use 2 ground cables I slide some red heat shrink tube on both ends so the customer knows which one is the + to avoid fitting the battery backwards .

When you do the terminals up protect them from water . no water = no corrosion
I paint over the ground contact ( ground = negative ) with black "Liquid Electrical Tape " and I do the same on the batteru, Black for the - and red for the +
You can use terminal grease or just plain old axel grease but the latter will derade over time .
Again you will see lots of stuff in auto stores electrical section

Now the mower
Remove the starter motor. clean where the mounting holes go against the engine nice & shinny and do the same at the engine then do it up tight.
IF it is a Briggs & Stratton engine you will need a Torx driver to get the front bolt off easily
Using your car & some jumper leads connect the - to the engine then touch the + to the post on the bottom of the starter to make it spin with out the spark plugs in
Spind it 5 times for 30 sec
IF the starter is too hot to touch then it is bad . it wil get hot but ot hot enough to burn your fingers .
Note the speed the engine turns.
Replace the spark plugs and repeat
the starter should spin a bit slower, around 2/3 to 1/2 the no plug speed and it should feel a bit hotter but again not too hot to touch

Note how the engine turns
IT should be a constant speed
If it goes slow fast -slow fast - slow fast then you have an engine problem

Get this done and get back to us for further instructions.
Your current battey is toast, if it got hot enough to melt the terminal post then internally it will be damaged.
With batteries it is a case of "bigger is better " so get the highest CCA rating mower battery that will fit in your case.
Down here there is only one but apparently in the USA there are several

As for You tube.
Taryl Fixes all ( ignore the silly start ups )
or
Donnyboy87
Are the best for those with no mechanical aptitude as they use plain language , take their time and explain everything as if the viewer knows nothing .

yes it is melted. If the battery was taken out then it could have been put back in backwards. If you are not mechanically inclined, and electrically inclined I would not attempt a repair. The problem with electrical repairs is that electrons do damage to some things instantly. If you find 4 or 5 things damaged, and miss one, it can happen again and you have to start over which can get expensive. You have a massive short somewhere I think. Theoretically a loose battery cable could arc and get hot but that damage looks worse than that. Looking at the photo, that post appears to have a "-" by it. Does the other one have a "+" ? I won't say much more but if a cable to the negative melts on a modern machine it probably means someone put the battery in backwards, or mice chewed thru both the negative and positive cable and they shorted together. Usually they don't run close together though. Positive ground machines are rare since the 1950's except in some British cars, and a negative ground to positive cable fault is rather rare excepting a starter shorting out internally. Backwards battery is more common.

Things melt from heat. Heat is caused by resistance. Resistance is caused by corrosion. You need to replace the battery AND the negative cable.

bertsmobile1 said:

Welcome
Could you tell us the make of engine fitted ?
If you do not know it then take a photo and post it .
Note most phone plhots will ned to be resized in a photo editing app
Make it 12 " along the longest side, set the resolution to 72 dpi and the file type jpg

You are correct, the batttery post has melted .
When high current ( amps ) is drawn through a conductor it generates heat
If you have plug in heater you would have noticed the power cord gets quite hot
A battery can be made to work as an arc welder
The electricity does not care weather you have a welding rod on the end or a starter motor
A starter motor is a dead short circuit across the battery terminals

This is one of the reasons why owners manuals tell you only to crank for 30 seconds continious then wait for a couple of minutes.
When wires get hot their resistance to passing high amps increases so you have a self feeding loop
The wires get hotter and draw even more amps which makes the wires hotter so it draws more amps which makes the wires hotter etc etc etc
And this includes the wires in the starter motor as well

Resistance to electric flow generates heat so dirty or corroded terminals generates heat
A faulty starter motor generates a lot more heat than a good one .

Loose terminals or a broken wire will cause sparks to happen
The only difference between a sparky joint and an electric welded is the amps

And the problem might not be at the battery terminal
usually a dag rusty ground connection at the mower end or a bad cable itself will be the problem
However it is just a case that the lead treminal on the end of the battery has the lowest melting point ( around 300 deg C )

SO there is your background now how to fix it
remove the battery cables ( cable = very thick wire ) one at a time at both ends
Polish them shinny check that the wire is tight in the terminal with no corrosion
If the end are grotty with lots of corrosion ( green / blue granules ) if more than 1/4 of the wires are broken away, replace the cables
I usually get automotive ones because they are cheaper than mower ones .
I don't know about USA shops but down here most ground cables have a flat bolt on terminal at both ends where as power cables alway s have a rouns terminal on one end.
When I use 2 ground cables I slide some red heat shrink tube on both ends so the customer knows which one is the + to avoid fitting the battery backwards .

When you do the terminals up protect them from water . no water = no corrosion
I paint over the ground contact ( ground = negative ) with black "Liquid Electrical Tape " and I do the same on the batteru, Black for the - and red for the +
You can use terminal grease or just plain old axel grease but the latter will derade over time .
Again you will see lots of stuff in auto stores electrical section

Now the mower
Remove the starter motor. clean where the mounting holes go against the engine nice & shinny and do the same at the engine then do it up tight.
IF it is a Briggs & Stratton engine you will need a Torx driver to get the front bolt off easily
Using your car & some jumper leads connect the - to the engine then touch the + to the post on the bottom of the starter to make it spin with out the spark plugs in
Spind it 5 times for 30 sec
IF the starter is too hot to touch then it is bad . it wil get hot but ot hot enough to burn your fingers .
Note the speed the engine turns.
Replace the spark plugs and repeat
the starter should spin a bit slower, around 2/3 to 1/2 the no plug speed and it should feel a bit hotter but again not too hot to touch

Note how the engine turns
IT should be a constant speed
If it goes slow fast -slow fast - slow fast then you have an engine problem

Get this done and get back to us for further instructions.
Your current battey is toast, if it got hot enough to melt the terminal post then internally it will be damaged.
With batteries it is a case of "bigger is better " so get the highest CCA rating mower battery that will fit in your case.
Down here there is only one but apparently in the USA there are several

As for You tube.
Taryl Fixes all ( ignore the silly start ups )
or
Donnyboy87
Are the best for those with no mechanical aptitude as they use plain language , take their time and explain everything as if the viewer knows nothing .

Click to expand...

Thank you so much for all this information! I appreciate you breaking it down so well for me. We will have to work through the process!

sgkent said:

yes it is melted. If the battery was taken out then it could have been put back in backwards. If you are not mechanically inclined, and electrically inclined I would not attempt a repair. The problem with electrical repairs is that electrons do damage to some things instantly. If you find 4 or 5 things damaged, and miss one, it can happen again and you have to start over which can get expensive. You have a massive short somewhere I think. Theoretically a loose battery cable could arc and get hot but that damage looks worse than that. Looking at the photo, that post appears to have a "-" by it. Does the other one have a "+" ? I won't say much more but if a cable to the negative melts on a modern machine it probably means someone put the battery in backwards, or mice chewed thru both the negative and positive cable and they shorted together. Usually they don't run close together though. Positive ground machines are rare since the 1950's except in some British cars, and a negative ground to positive cable fault is rather rare excepting a starter shorting out internally. Backwards battery is more common.

Click to expand...

Totally fair question! Yes, the battery terminals are labeled + and - and we installed the battery with the red cable connected to + and the black to the -. When you say a loose battery cable... We may not have installed the little flat rings (spades?) of the cables absolutely bolted flat against the post. I think we thought as long as there was a metal to metal connection it didn't matter whether the spade was in full contact with the post because it was in contact with the bolt that was in contact with the post? But I suppose that was incorrect? Are you saying that could have cause an arc and cause the melting?

I am confident we didn't install the battery backwards but again, maybe not as tight as we should have. You may be right that it is beyond what we should attempt on our own; if there is a short deeper in the machine we could easily miss it. We're not opposed to getting help, just trying to learn and do what we can. Thank you so much for your information

bertsmobile1 said:

Welcome
Could you tell us the make of engine fitted ?
If you do not know it then take a photo and post it .
Note most phone plhots will ned to be resized in a photo editing app
Make it 12 " along the longest side, set the resolution to 72 dpi and the file type jpg

You are correct, the batttery post has melted .
When high current ( amps ) is drawn through a conductor it generates heat
If you have plug in heater you would have noticed the power cord gets quite hot
A battery can be made to work as an arc welder
The electricity does not care weather you have a welding rod on the end or a starter motor
A starter motor is a dead short circuit across the battery terminals

This is one of the reasons why owners manuals tell you only to crank for 30 seconds continious then wait for a couple of minutes.
When wires get hot their resistance to passing high amps increases so you have a self feeding loop
The wires get hotter and draw even more amps which makes the wires hotter so it draws more amps which makes the wires hotter etc etc etc
And this includes the wires in the starter motor as well

Resistance to electric flow generates heat so dirty or corroded terminals generates heat
A faulty starter motor generates a lot more heat than a good one .

Loose terminals or a broken wire will cause sparks to happen
The only difference between a sparky joint and an electric welded is the amps

And the problem might not be at the battery terminal
usually a dag rusty ground connection at the mower end or a bad cable itself will be the problem
However it is just a case that the lead treminal on the end of the battery has the lowest melting point ( around 300 deg C )

SO there is your background now how to fix it
remove the battery cables ( cable = very thick wire ) one at a time at both ends
Polish them shinny check that the wire is tight in the terminal with no corrosion
If the end are grotty with lots of corrosion ( green / blue granules ) if more than 1/4 of the wires are broken away, replace the cables
I usually get automotive ones because they are cheaper than mower ones .
I don't know about USA shops but down here most ground cables have a flat bolt on terminal at both ends where as power cables alway s have a rouns terminal on one end.
When I use 2 ground cables I slide some red heat shrink tube on both ends so the customer knows which one is the + to avoid fitting the battery backwards .

When you do the terminals up protect them from water . no water = no corrosion
I paint over the ground contact ( ground = negative ) with black "Liquid Electrical Tape " and I do the same on the batteru, Black for the - and red for the +
You can use terminal grease or just plain old axel grease but the latter will derade over time .
Again you will see lots of stuff in auto stores electrical section

Now the mower
Remove the starter motor. clean where the mounting holes go against the engine nice & shinny and do the same at the engine then do it up tight.
IF it is a Briggs & Stratton engine you will need a Torx driver to get the front bolt off easily
Using your car & some jumper leads connect the - to the engine then touch the + to the post on the bottom of the starter to make it spin with out the spark plugs in
Spind it 5 times for 30 sec
IF the starter is too hot to touch then it is bad . it wil get hot but ot hot enough to burn your fingers .
Note the speed the engine turns.
Replace the spark plugs and repeat
the starter should spin a bit slower, around 2/3 to 1/2 the no plug speed and it should feel a bit hotter but again not too hot to touch

Note how the engine turns
IT should be a constant speed
If it goes slow fast -slow fast - slow fast then you have an engine problem

Get this done and get back to us for further instructions.
Your current battey is toast, if it got hot enough to melt the terminal post then internally it will be damaged.
With batteries it is a case of "bigger is better " so get the highest CCA rating mower battery that will fit in your case.
Down here there is only one but apparently in the USA there are several

As for You tube.
Taryl Fixes all ( ignore the silly start ups )
or
Donnyboy87
Are the best for those with no mechanical aptitude as they use plain language , take their time and explain everything as if the viewer knows nothing .

Click to expand...

It is a Briggs and Stratton Engine - model number 313707

Yes the terminals must be flat against each other and not being in full contact can cause arcing
The watr analogy is tipping a ful bucket of water through a narrow funnel
Some will pour over the sides if enough can not get through the small hole .

bertsmobile1 said:

Yes the terminals must be flat against each other and not being in full contact can cause arcing
The watr analogy is tipping a ful bucket of water through a narrow funnel
Some will pour over the sides if enough can not get through the small hole .

Click to expand...

That makes sense, thank you all! The spade and bolt weren't tight against the post when we found the problem yesterday. My husband says he thinks we did install it snugly (but that would have been three years ago). I guess we will need to figure out the chicken/egg question - did it jostle loose over time, heat up and melt the terminal, or did some other problem (a deeper short) melt the terminal and cause the gap/loose connection (because the post changed shape)? You all have given us great information to get started, I appreciate it!

FWIW I fit a long stainless coach bolt to hold the battery terminals on
because of the square section under the heat the bolt makes a good contact with the post .
I use a wing nut to hold the terminal to the post then paint over the whole lot with "liquid Electrical tape " thus the different metals can not form a galvanic cell
The end of the long bolt that hangs out is left bare so there is a place to put jumper leads on if required without disturbing the terminal.
The Liquid Electrical tape also prevents the nut coming loose .