6 Starters on 2012 bmw 135

The first time, it wouldn’t crank when warm. Took it to the dealer under an extended warranty, he replaced the starter. Within a week it happened again. This time he thought he had it, called me in, but it wouldn’t start after they washed it before returning it to me. Third time they had it for 3 weeks. Replaced alternator twice, and starter 3 times. Found corroded cable.

After a couple of years, it’s started happening again. Went to an independent shop, he replaced the starter and also found a corroded cable. After 4 weeks it happened again. The independent shop did it again, for free (they warranty their work). Also said they found loose cable.

Any idea what can really be causing this? How can a loose/corroded cable cause the starter to break? They all bench-tested the starter, and found it bad.

Electric motors don’t do well with voltages a lot lower than they are designed for.

Next time it won’t crank ask you shop to measure the voltage on the 2 terminals which connect power to the starter. Probe at the starter motor itself, between the terminal and the starter case. Both should be 10.5 volts or above w/the key in “start”. If they are and the starter doesn’t crank the engine, either the starter motor is faulty or the engine is seized. If one or both are less than 10.5 volts, work backwards from the starter towards the battery to find out why. Years ago I had a faulty wiring harness in my Corolla caused by battery acid eating through a solder splice deep inside the harness that caused similar symptoms. Other problems could cause this, besides a faulty starter motor or bad harness, but until you know the results of the voltage test above it’s not gonna be possible to give much more direction.

Good Idea, thanks! I was thinking that this may be worth doing before the “next time”. Once the starter is dead, it may not load the connection.

The more data you have for comparison purposes the better. Here’s something a little scary which might be related to your problem: In the past 6 years I’ve purchased two aftermarket starter motors from auto parts stores that failed right out of the box. I’m just a diy’er, don’t buy very many starter motors. So don’t discount the idea that the parts you are buying are just poorly made and no good from the get go. I’ve had best luck w/Toyota and Denso branded starter motors, if that’s of any help.

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