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  #1  
Old 08-24-2014, 05:29 PM
Redefining normal daily
 
Join Date: Jul 2004
Location: Frederick, MD
Posts: 445
Question for the Sparkies

Got a Cub Cadet LT1050..... with what I assume to be a dead starter. Looking for confirmation or correction please.



Apparent short between the housing and the positive lead. For the record, solenoid on these is mounted remotely.

Took the starter apart, found a suspect lead - worn insulation (starts at the 3:00 position in the photo below). I was able to recreate a short between opposing leads/brushes by wiggling and squeezing.



Repaired the insulation, and confirmed no shorts between opposing leads/brushes. Put everything back together, still getting a dead short between the positive lead and the starter housing.

If I put 12VDC across the positive lead and housing on the bench, the starter spins freely. Bolt the starter back in the mower, hit it with 12VDC again, it spins - but slowly and with great protest.

Theories? Suggestions?
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1961 220b: first project car - sold.
2000 CLK 430: first modern Benz - sold.
2001 CLK 55: OMG the torque!!! - sold
1972 280SE 4.5: Baby Gustav
1991 300TE 4Matic: Gretel the Snow Bunny - sold
1978 300SD: Katz the Free Man
1980 Redhead: Darling Wife
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  #2  
Old 08-24-2014, 05:44 PM
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Join Date: May 2011
Location: NYC
Posts: 5,192
If it's not a weak battery, allowing the starter to bog down under load, it sounds like an internal short in the windings. It's not a dead short, but some of the windings are "bypassed", making the starter weaker. Are you hitting it with 12V on the tractor directly from a battery, in order to rule out a solenoid issue?

BUT ... 0.06Ω is not actually out of line for a starter motor, especially since resistance measurements can be iffy near zero ohms. You'd assume that it would draw 2000A+ at 12V with that kind of resistance, but remember that there's also back EMF which cuts down on effective voltage and internal resistance in the battery.
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  #3  
Old 08-24-2014, 06:34 PM
Redefining normal daily
 
Join Date: Jul 2004
Location: Frederick, MD
Posts: 445
12VDC via robust jumper cables from a running Miata to positive lead on the starter and ground on the tractor (starter housing).

Is there any practical why to get a good/bad call on the starter motor before pulling the trigger on a replacement?
__________________
1961 220b: first project car - sold.
2000 CLK 430: first modern Benz - sold.
2001 CLK 55: OMG the torque!!! - sold
1972 280SE 4.5: Baby Gustav
1991 300TE 4Matic: Gretel the Snow Bunny - sold
1978 300SD: Katz the Free Man
1980 Redhead: Darling Wife
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  #4  
Old 08-24-2014, 06:40 PM
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Join Date: May 2011
Location: NYC
Posts: 5,192
Take it to an electric motor shop and they can use a growler to test for shorted windings.
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  #5  
Old 08-24-2014, 07:15 PM
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Join Date: Oct 2007
Location: St. Thomas PA
Posts: 957
A starter is basically a dead short. Try cranking the engine with the plug removed. If it's OK, it's not the starter. Verify that the compression release is working and check the valve clearance. If the clearance is too large, the CR will be ineffective.
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  #6  
Old 09-01-2014, 10:32 AM
Redefining normal daily
 
Join Date: Jul 2004
Location: Frederick, MD
Posts: 445
Update: new starter ordered and received... 0.2 ohms case to positive lead.

Bolted it in, and all systems go.

Amazing how much healthier it sounds starting now.... catches and goes first bump every single time.
__________________
1961 220b: first project car - sold.
2000 CLK 430: first modern Benz - sold.
2001 CLK 55: OMG the torque!!! - sold
1972 280SE 4.5: Baby Gustav
1991 300TE 4Matic: Gretel the Snow Bunny - sold
1978 300SD: Katz the Free Man
1980 Redhead: Darling Wife
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