Weird electrical problems after starter replacement

[sapote]

A bad ground can cause all sorts of issues. It can work one day and be completely dead the next. It can cause a short to ground that drain a battery in no time.

I think we're talking about the engine ground strap connecting engine/tranny to the chassis frame here. If this ground cable is bad enough to cause the alternator not able to charge the battery at typical 10A current, then how does the same bad ground can crank the engine at 300A by the starter? So mu logic is that if it is good enough to carry 300A cranking current then it should have no problem to carry 10A charging the battery.

How can a bad engine ground cable can cause a short to ground (what is shorted to ground?) and drain a battery?

[Kcalhoun27]

I think we're talking about the engine ground strap connecting engine/tranny to the chassis frame here. If this ground cable is bad enough to cause the alternator not able to charge the battery at typical 10A current, then how does the same bad ground can crank the engine at 300A by the starter? So mu logic is that if it is good enough to carry 300A cranking current then it should have no problem to carry 10A charging the battery.

How can a bad engine ground cable can cause a short to ground (what is shorted to ground?) and drain a battery?

So, i think we are not on the same page, probably my fault. A short to ground is a short circuit, in this case, from the harness. What im suggesting is that the potential for the ground harness to have a loose or failed connection is causing the intermittent completion of a circuit and that is leading to the problems he is having. The intermittent part is what makes me think this. He is having multiple issues that are only related to electrical power delivery. So yes, the ground cable from the engine to the body might be fine. But the actual ground harness from the starter to the altenator or from the battery could be loose or damaged. Were it my car, i would remove and inspect the ground wires to see if one is damaged, then make sure i installed the with clean metal and tight fittings. Thats all.

Again, not saying this is guaranteed the issue, but i have personally seen issues like this result from poor ground connections. Like you, im trying to keep learning and hand off any experiences ive had that might help

[George Hill]

The alternator charging wire connects to the starter, from there it has to go from the starter to the jump start terminal. If either of these are loose or not connected properly it will give all of the symptoms you are mentioning. I would 100% audit the starter replacement as the first step.

[sapote]

when replacing a starter, is it possible that they screwed something up that’s causing this?

There is a big cable connecting from the alternator to the starter by the nut, and another longer cable from the same point on starter to the fender jumper post. If the said nut is not tight then alternator cannot charge the battery properly, and this also can cause the starter current having too much resistance.

There is absolutely no ground harness connecting from starter to the alternator, as both are already bolted to chassis ground and don't need any ground wires or harness.

[Nico]

The alternator charging wire connects to the starter, from there it has to go from the starter to the jump start terminal. If either of these are loose or not connected properly it will give all of the symptoms you are mentioning. I would 100% audit the starter replacement as the first step.

Thank you!

[Nico]

Have you tested the alternator and battery? I've had rebuilt alternators that failed in about that timeframe.

Just heard back from my Indy and it was the alternator. Battery was toast too.

The alternator that I got a couple years ago was Bosch. My mechanic told me that the OE unit was valeo and the boschs were rebuilt units. Is this true?

[George Hill]

I have not had good luck with reman Bosch alternators and starters. I never install them if I can help it as I replace as many of those as I do original starters/alternators. Pre-Covid we could get Valeo alternators but they are NIS anywhere that I can find right now.

[Nico]

I have not had good luck with reman Bosch alternators and starters. I never install them if I can help it as I replace as many of those as I do original starters/alternators. Pre-Covid we could get Valeo alternators but they are NIS anywhere that I can find right now.

Yup, did some looking and it seems not many people have had their replacement Bosch alternators last long at all. Makes sense. Hopefully they can find one.

[sapote]

The alternator that I got a couple years ago was Bosch. My mechanic told me that the OE unit was valeo and the boschs were rebuilt units. Is this true?

Bosch and Valeo used different connectors, and so if the original was Valeo then your replacement is also Valeo (made by Valeo) but might be rebuilt by Bosch with its sticker (on the old Valeo unit).

[George Hill]

Bosch and Valeo used different connectors

That is incorrect if you are talking about the connector to the engine harness, if you aren't then I'm not sure what you are referring to in regards to Nico's situation.

Bosch and Valeo used different connectors, and so if the original was Valeo then your replacement is also Valeo (made by Valeo) but might be rebuilt by Bosch with its sticker (on the old Valeo unit).

But you are correct as far as I know all the reman Bosch alternators started off originally as Valeos

[SocratesRising]

I would have guessed your ignition switch was bad, good you have it figured out.

Sent from my Pixel 4 XL using Tapatalk

[sapote]

That is incorrect if you are talking about the connector to the engine harness, if you aren't then I'm not sure what you are referring to in regards to Nico's situation.

I'm talking about the plastic housing connector at the back of the alternator. One is rectangular and the other has the oval shape. This configuration is on most E46 cars but might be the M3 is an exception.