1999 mercedes benz sl500 starting problem - Mercedes-Benz Forum
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post #1 of 4 (permalink) Old 06-17-2019, 05:15 PM Thread Starter
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Vehicle: 1999 mercedes benz sl500
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1999 mercedes benz sl500 starting problem

I just finished putting in a conductor plate, because the car was in limp mode and seriously needed it and I was going to do a transmission flush. I hooked up the battery to start it and when my son turned the key sparks flew from the starter area, I took a picture of the starter and I have posted it here. The wire from the solenoid to the starter is melted . The car dash lights up as if everything is ok but when I turn the key all the way nothing no clicks or anything. 1. What could have caused this( Could it have arched from another wire?) 2. did I fry the starter. 3. what else could I have fried.

Thank You for your help
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post #2 of 4 (permalink) Old 06-17-2019, 06:11 PM
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The only explanation for that wire melting I believe has to be a faulty motor starter. But I would suspect the problem to be associated with your transmission work, and the starter is unrelated.

You might have blown fuse #15. It supplies current to the starter solenoid.

I would check the resistance of the motor starter's armature windings by measuring resistance from the burnt wire to chassis ground. I don't know what you can expect to read, but if you post your findings, the forum may be able to draw conclusions. Alternatively, you might just go ahead and install a replacement motor starter.
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post #3 of 4 (permalink) Old 06-18-2019, 01:35 AM
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I would expect the windings to have low resistance normally. Open circuit would clearly suggest defective windings. You have probably damaged the brushes/commutator in the starter, but the root cause of the problem is most likely to be your recent transmission work.

It is possible therefore that the flywheel was jammed, preventing the starter from turning and a sudden build up of very large current when you tried to start the engine.

Did the manage to turn the engine over at all?

With a socket on the main crank pulley but, is it possible to turn the engine over slowly? You probably should remove the spark plugs first.
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post #4 of 4 (permalink) Old 06-18-2019, 10:21 AM
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First assumption is that your burned wire is the fat one that provides motive current to the starter. If the burn is on the control wire to the solenoid, replace the solenoid and have fun. Now then, it sounds like either a locked rotor because of a mechanical failure of some sort, or a shorted windings in the starter. Basic rule, fuses don't blow themselves, and once blown there is no current flow. In the circuit you are talking about here (the fat wire) that is the fuse as that circuit is not usually fused, only the control signal is. Resistance on a DC motor is close to 0 if you check it with an ohmeter. Infinite says it is already burned open. The burned wire tells us that a lot of current was going through that wire which made it get hot. Very analogous to the filament in a light bulb. If you hook a shunt resister in series with the fat wire going to the starter, what you should see is when you first hit it, a large current flow that dies off immediately when the motor starts to turn. If it does not turn, it will get very hot very quickly and eventually blow the fuse if there is one in that circuit. All that to say, if you have locked it up, you probably toasted the starter motor. If the starter was bad anyway, you probably have a bad starter. Either way, you will need a new starter, but make sure the mechanics are not bound or you will toast the new starter motor as well (an expensive lesson). As to the sparks from your starter, they do not indicate one way or the other. Both situations could cause that. Also, on the fuse to the solenoid ... That has nothing to do with anything, unless that is the wire that is burned, and the fuse should have blown. But, if that were the case, turning the key would result in nothing more than the sound of crickets perhaps ... Oh yeah, replace the burned wire with the same gauge wire as before or a larger gauge (smaller number). That burned wire is unsafe for a number of reasons.
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