ke8fyf
New member
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- Ocqueoc, MI
Hello all,
I recently picked up an as-is MEP831a from a collector I know (he normally deals with larger sets). There was a hard to crank condition which was originally thought to be an engine issue but upon further inspection I saw the rotor of the PMA was hitting the stator. I made a puller and removed the rotor and reseated the stator and carefully put the rotor back in. I did not shim it up, I just checked runout with a dial indicator and it was within .003" to which I figured would be good enough.
I started the engine and as it burned off all the smudge (it had been sitting outside), I started to get a burning electrics smell and saw a wisp of smoke out of the top of the PMA. I shut the engine down and the top of the PMA was hot to the touch.
Pulled it apart and saw this particularly black looking section but it doesn't seem as if any of the kapton tape had burned. (see photo). This segment was oriented at the top when installed and this is the side against the engine.
I went through the procedure in the TM as far as checking the windings. Per page 4-51 I did the first test of measuring resistance between similar number windings. Just to confirm this would be A1 to B1, B1-C1, A1-C1, etc (checking pairs in the same horizontal row). I should mention I am using a Harbor Freight DMM for the time being as its all I have. In connector P15 I was consistently getting of 1.9 ohms. In P16 they usually around 1.6ohm The TM lists that they should be below 1.2 The DMM reads 1.3 just touching the leads together, is it safe to chalk up this discrepancy to poor measuring equipment? The second part of checking between windings (pairs vertically) passes on P15 but on P16 the meter transitions from open to just displaying 0. I am on the 2m scale when doing this. I have not moved past this point as the next tests are with the system running and I don't want to risk totally frying this thing.
Just trying to figure out if my problem was friction heating it up or do I have a short somewhere? I have not checked circularity of the stator or the rotor. This did rub together at one point but the witnesses on each lead me to believe it wasn't for any extended amount of time. The magnets are still QUITE strong. I plan on reinstalling but shimming .010" between the two. Pretty sure I have some austenitic shim stock somewhere.
I recently picked up an as-is MEP831a from a collector I know (he normally deals with larger sets). There was a hard to crank condition which was originally thought to be an engine issue but upon further inspection I saw the rotor of the PMA was hitting the stator. I made a puller and removed the rotor and reseated the stator and carefully put the rotor back in. I did not shim it up, I just checked runout with a dial indicator and it was within .003" to which I figured would be good enough.
I started the engine and as it burned off all the smudge (it had been sitting outside), I started to get a burning electrics smell and saw a wisp of smoke out of the top of the PMA. I shut the engine down and the top of the PMA was hot to the touch.
Pulled it apart and saw this particularly black looking section but it doesn't seem as if any of the kapton tape had burned. (see photo). This segment was oriented at the top when installed and this is the side against the engine.
I went through the procedure in the TM as far as checking the windings. Per page 4-51 I did the first test of measuring resistance between similar number windings. Just to confirm this would be A1 to B1, B1-C1, A1-C1, etc (checking pairs in the same horizontal row). I should mention I am using a Harbor Freight DMM for the time being as its all I have. In connector P15 I was consistently getting of 1.9 ohms. In P16 they usually around 1.6ohm The TM lists that they should be below 1.2 The DMM reads 1.3 just touching the leads together, is it safe to chalk up this discrepancy to poor measuring equipment? The second part of checking between windings (pairs vertically) passes on P15 but on P16 the meter transitions from open to just displaying 0. I am on the 2m scale when doing this. I have not moved past this point as the next tests are with the system running and I don't want to risk totally frying this thing.
Just trying to figure out if my problem was friction heating it up or do I have a short somewhere? I have not checked circularity of the stator or the rotor. This did rub together at one point but the witnesses on each lead me to believe it wasn't for any extended amount of time. The magnets are still QUITE strong. I plan on reinstalling but shimming .010" between the two. Pretty sure I have some austenitic shim stock somewhere.
