4amp draw- high pitched whine from engine compartment- ignition off

[gluaisrothaii]

Had a dead battery today. Drove the car quite recently- yesterday. Quick boost charge to start, alternator came up fine. Battery charged on a 30 minute drive.

Post driving I shut down and heard a high pitched whine from the engine compartment. Not the CS, ISC or FV. Pulled plugs from those and whine and load remained. Ballast resistor was cool so not the coil. Connected up an instrumented power supply, disconnected the battery and saw a 3.8-4.1 amp consistent load along with the whine. Pulled fuses to troubleshoot-either 4, 10 or 16 eliminated the issue (or just coincidental timing) but the load was gone when I plugged the fuses back in. Didn't get to pull the WUR plug before the whine stopped, and the 4 amp load was gone.

Any ideas?


Best,
Ken

[Michael]

Alternator is taking a puke. It can still charge and be burnt up. Most likely driving with a very low battery finished it off.


Edit: oh this was after the engine stopped? Scratch the alternator if that's the case.

[gluaisrothaii]

Alternator is taking a puke. It can still charge and be burnt up. Most likely driving with a very low battery finished it off.


Edit: oh this was after the engine stopped? Scratch the alternator if that's the case.

Alternator would be annoying. It's brand new from DMCH. 300 miles. Whine was there with the engine off.

Just to clarify- alternator is topping battery off easily while driving, and running the lights etc, and the vehicle runs just fine. When turned off there's (sometimes) a real 4 amp electrical load that is depleting the battery. Something like a stuck relay. Whatever is consuming the power makes a high pitched whine in the engine compartment and doesn't show any signs of doing anything useful with the power.

[DMC-81]

That's an odd problem. There is a relay below and to the left of the ballast resistors (see pic). Is yours present? If so, I would perhaps check that.



I pulled that relay one time to do some troubleshooting and the car did not stall.

Other than that, I wonder if your starter solenoid is slightly sticking (just a shot in the dark).

[gluaisrothaii]

Alternator would be annoying. It's brand new from DMCH. 300 miles. Whine was there with the engine off.

Just to clarify- alternator is topping battery off easily while driving, and running the lights etc, and the vehicle runs just fine. When turned off there's (sometimes) a real 4 amp electrical load that is depleting the battery. Something like a stuck relay. Whatever is consuming the power makes a high pitched whine in the engine compartment and doesn't show any signs of doing anything useful with the power.

By unplugging every other noise maker in the engine bay I have isolated the whine to the alternator. It whines with the ignition on, and stops when I pull the charge light connector out (brown/yellow vehicle wire). 4 amps would make sense for full field current. Why/how would the alternator turn on field current with the ignition off?

[DMC-Ron]

By unplugging every other noise maker in the engine bay I have isolated the whine to the alternator. It whines with the ignition on, and stops when I pull the charge light connector out (brown/yellow vehicle wire). 4 amps would make sense for full field current. Why/how would the alternator turn on field current with the ignition off?

Check to see if + voltage on the brown wire going to the voltage regulator is turning off with the ignition switch. If you have power with the key off. disconnect the brown wire and test to see if the power is coming from the ignition circuit (brown wire) or feedback from the alternator thru the regulator. Power at the brown wire's alternator connector would indicate internal short in the alternator voltage regulator. Power on the brown wire would incriminate the auxiliary relay (It supplies power to the alternator regulator but should only be engaged when the key is on).

Ron

[Bitsyncmaster]

My guess would also be the alternator is bad. The 4 amp load does sound about right for the field current and the wine must be the regulator is switching that current on and off.

[gluaisrothaii]

That's an odd problem. There is a relay below and to the left of the ballast resistors (see pic). Is yours present? If so, I would perhaps check that.



I pulled that relay one time to do some troubleshooting and the car did not stall.

Other than that, I wonder if your starter solenoid is slightly sticking (just a shot in the dark).

Thanks- I had previously replaced that relay and it does not seem to be the source of the issue.

[gluaisrothaii]

Check to see if + voltage on the brown wire going to the voltage regulator is turning off with the ignition switch. If you have power with the key off. disconnect the brown wire and test to see if the power is coming from the ignition circuit (brown wire) or feedback from the alternator thru the regulator. Power at the brown wire's alternator connector would indicate internal short in the alternator voltage regulator. Power on the brown wire would incriminate the auxiliary relay (It supplies power to the alternator regulator but should only be engaged when the key is on).

Ron

My guess would also be the alternator is bad. The 4 amp load does sound about right for the field current and the wine must be the regulator is switching that current on and off.

Hi Ron, Dave,
With the 140 Amp DMCH alternator only the brown/yellow wire is used to trigger the regulator to turn on. This is the ground side of the charging lamp on the instrument panel. The brown wire from the aux relay is terminated inside the harness. Though it is not documented by DMCH, it seems to be optional to use the brown as a voltage sense line so that the VR drives to 14.8V at the battery rather than just at the B+ post of the alternator.

As a test later on today I'll hook up a variable voltage source to the L input on the alternator to see what it takes to turn it on and confirm that it draws 4 amps in that state.

Best,
Ken

[DMC-81]

Hi Ron, Dave,
With the 140 Amp DMCH alternator only the brown/yellow wire is used to trigger the regulator to turn on. This is the ground side of the charging lamp on the instrument panel. The brown wire from the aux relay is terminated inside the harness. Though it is not documented by DMCH, it seems to be optional to use the brown as a voltage sense line so that the VR drives to 14.8V at the battery rather than just at the B+ post of the alternator.

As a test later on today I'll hook up a variable voltage source to the L input on the alternator to see what it takes to turn it on and confirm that it draws 4 amps in that state.

Best,
Ken

Hi Ken,

That is correct. I connected the brown wire to get rid of the flashing test sequence with the ignition on, but not started. There is more info here: http://dmctalk.org/showthread.php?12181-DMCH-alternator .