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55 volt supply voltage goes up to 68 volts at idle E-TEC I-3
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2 posts 440 2 posts
440
E75DSLII ser # 5312800 when engine idles in neutral 55volt supply voltage rises to 68 any increase in rpm goes back to 55. Ohmed harness. Replaced stator and capacitor. Any help before I replace emm.results from stator output test was 31 volts ac @325 rpm. Engine sets code 18 and goes in safe mode.12.3 volts at idle about 13.8 when cruising any ideas or suggestions. Thanks
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Huey Moderator 14,334 posts
Huey
What are the test results when you do the required stator output test?
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WernerF 127 posts
WernerF
As far as I can see the Stator Test Adapter Tool mentioned in the service manual connects leads 2 with 3 and lead 4 with 5. So measuring leads 1 and 6 the three stator windings are series connected.
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jimh 7,578 posts
jimh
440 wrote:
...when engine idles in neutral [55-Volt] supply voltage rises to 68 [but with] any increase in rpm goes back to 55.


The E-TEC uses a permanent magnet alternator (PMA). The voltage output of a PMA is proportional to rotation speed.

The alternator has three windings. At low speeds when the voltage being created in each winding is low, the three windings are connected  by the EMM in series to create a higher voltage.

As engine speed increases, the voltage being produced in each winding increases. The EMM changes the windings to be connected in parallel. This creates more current available for output.

This change may explain why the measured voltage you recorded was higher at idle speed than it was at a higher engine speed.

I don't know the details of the voltage regulation circuitry. I don't know the details of how you performed the voltage measurement you state.
As of 2024 I am no longer making legacy E-TEC engine EV-Diagnostic cables .
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440 2 posts
440
440 wrote:
E75DSLII ser # 5312800 when engine idles in neutral 55volt supply voltage rises to 68 any increase in rpm goes back to 55. Ohmed harness. Replaced stator and capacitor. Any help before I replace emm.results from stator output test was 31 volts ac @325 rpm. Engine sets code 18 and goes in safe mode.12.3 volts at idle about 13.8 when cruising any ideas or suggestions. Thanks
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steelhead 5,065 posts
steelhead

Does the voltage on the + terminal on the large blue capacitor also measure 68V?
Any AC voltage ripple on the + terminal?

On the EV Diagnostics Monitor page what shows for charge V and charge current when the system V goes to 68v?
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