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stickman007

Alternator Operation and Related Issues

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Just wanted to think aloud here and hopefully bounce ideas off the community.

 

I've heard and seen a few 450s that seems to over crank. I have no real explanation for this phenomenon until I've recently gotten a clue - a bad alternator. A bad alternator seems to be related to the over cranking as the ECU doesn't seem to recognize that the engine is running. I've been working on a car that seems to have developed this over cranking issue just as the alternator died.

 

I believe that the ECU relies on the crank position sensor to read the rpm, but I don't think the ECU use that information to "confirm" that the car is running. I think its the "DF" signal (white wire) that sends a pulse to the ECU to let it know when the engine is running as well as load.

 

I'm currently waiting for a new alternator. If the problem clears up, I maybe able to confirm this?

 

Any electrical gurus out there that can chime in?

 

Izzy

 

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Guess I was wrong. The new alternator came in, and I installed it last nite (what a miserable job). The over cranking still happens, but to a lesser degree, but I don't think the 2 are related. If anything changes, I will report back.

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Just for documentation purposes...had to piece information from fq101 and evilution:

 

SAM to Alternator N11-8 pin7 (Black/Yellow) - I'm assuming that it goes to the "L" and should get ignition 12v

Alternator to ECU Pin47 (white, lower connector) - I'm assuming that it goes to "FR" and basically how the ECU controls load

 

 

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