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.

http://dmctalk.org/attachment.php?attachmentid=61847&d=1574554190

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.

http://dmctalk.org/attachment.php?attachmentid=61847&d=1574554190

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 .

[gluaisrothaii]

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 .

Thanks! Read through that....weirdly I do not have the flashing test sequence. I wonder if there's a new rev of the regulator.

Best,
Ken

[dmcnc]

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.

I had the same issue with the DMCH alternator - it's more of a high frequency noise the engine was off. It killed a battery or two before I figured out it was the alternator. I would either get it replaced or go for another option.

[gluaisrothaii]

I had the same issue with the DMCH alternator - it's more of a high frequency noise the engine was off. It killed a battery or two before I figured out it was the alternator. I would either get it replaced or go for another option.

Wow! Thanks for that. I'll give them a call right now.

Ken

[gluaisrothaii]

Looks like the feed through the #191 bulb in the panel results in a 3 volt signal to the +L line on the alternator. Playing around with a potentiometer I was able to pull the alternator regulator online with a 0.4 volt signal- that's a low as I could go with the pot I had on hand (turned all the way down with a 1.5AA battery as the supply). It might come on with less that that. Seems like the alternator might be a little sensitive to something like a bad ground holding the voltage up on that feed line...

[Patrick C]

I had this EXACT problem with my DMCH alternator this fall! I went out to the garage and could hear a high pitched whining coming from the engine bay. I tried a lot of troubleshooting, but the whining noise seemed to go away on its own, but I’m not confident it’s gone for good.

[Michael]

For what it's worth when my DMCH alternator quit a few weeks ago it had a whine to it but it still charged at higher rpm. Low rpm was nothing. (I don't recall hearing any noise when the engine was off however).
I doubt I will never buy another alternator as long as these local guys rebuild it like they did this one. Almost 15v on the gauge at idle and in almost 11 years and 3 alternators I have never had the confidence to run the AC at night because with lights and ac fans, I would go into single digits.

My advice (which I followed from another member) is have yours rebuilt by a reputable place. Try to find a rebuilder that uses American components and has been in business for some time.

My rebuild cost $90.00 and it came back cleaned looking brand new and with a new pigtail.

[Bitsyncmaster]

Thanks! Read through that....weirdly I do not have the flashing test sequence. I wonder if there's a new rev of the regulator.

Best,
Ken

That is interesting that the DMCH unit now does not flash the error code (If sense is no hooked up). I wonder if DMCH is stocking a new alternator or if the manufacture changed the regulator.

[gluaisrothaii]

All,
Issued resolved- seems like a problem with the new alternator. DMCH replacement was sent and installed; all is good. Great service from DMCH! No more whining from the alternator with the ignition off.

Best,
Ken

[CFI]

All,
Issued resolved- seems like a problem with the new alternator. DMCH replacement was sent and installed; all is good. Great service from DMCH! No more whining from the alternator with the ignition off.

Best,
Ken

Lol, great service? Great service would have been sending a quality alternator the first time around :)

[Patrick C]

I wonder if this is a known flaw with the DMCH alternator. If mine is still doing this in the spring when I pull it out of storage, I’ll have to contact them for a replacement.

[gluaisrothaii]

All,
Issued resolved- seems like a problem with the new alternator. DMCH replacement was sent and installed; all is good. Great service from DMCH! No more whining from the alternator with the ignition off.

Best,
Ken

I spoke too soon. The ignition-off whine is back, and battery has gone dead twice on me with the new alternator. Same symptoms as before. I had to revert to disconnecting the battery at night.

[Bitsyncmaster]

I spoke too soon. The ignition-off whine is back, and battery has gone dead twice on me with the new alternator. Same symptoms as before. I had to revert to disconnecting the battery at night.

Maybe you have a sticking relay. Try unplugging them until the whine goes away.

[gluaisrothaii]

Maybe you have a sticking relay. Try unplugging them until the whine goes away.

The implication being some stray voltage passing through the L line and activating the alternator? I have checked and seen 0v there with IG off, but that doesn't mean there's occasionally something there....

No...the only draw is through the alternator main feed. That is not on a relay, it's direct to the battery. If the main or aux relays were sticking I would see power draw with the alternator isolated- and I don't.


Others have reported a similar issue with the DMCH alternator in this thread, so there must be something odd about the interaction of the vehicle's wiring and the regulator in this alternator..but of course there's nothing magical with the control circuit. I might try a forward biased diode on the L line. The breakdown voltage would have a high enough threshold to cut off stray voltage that might be holding the regulator on with IG off. Either that or a high value resistor to ground in parallel with the L line to zero out the line once the ignition is off.

[David T]

Pull the alternator and have it bench tested. Recheck the wiring to the alternator. As a stop-gap alternative you can install a battery master switch.

[Michael]

A lot of rebuilders take short cuts. They may look for broken coating on the windings, pry apart what they can see and just re coat what it visible instead of actually rewinding the rotor.

A good rebuild will be with fresh windings.

[Ron]

I was following this when it seemed to be resolved. Food for thought:

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....


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.

With the original alternators, the Brown wire is normally connected to AUX #2 Relay. Using the same terminal, it also feeds the BATT light via a Green wire through Fuse #5.
(! not 4, 6, 10 ???)

I'm suspecting PO mods e.g a radio's Always Hot Power/Memory wiring for the radip etc crossed up....Something feeding the regulator on a common circuit... Maybe see what happens if fuse #5 only is pulled.

(I'd jump the sense wire to the Main Alternator post, if not using the Brown wire even though all of the alternators I've seen so far with the feature have it virtually connected internally....)

FWIW-
Make sure the BATT bulb is correct. The wrong incandescent or a LED causes problems.

When you hear the sound, look VERY carefully at the BATT light for a faint glow.
If it does, the little diode trio/regulator in the alternator may be getting zapped...or defective Alternator #2.

[Ron]

A lot of rebuilders take short cuts. They may look for broken coating on the windings, pry apart what they can see and just re coat what it visible instead of actually rewinding the rotor.

A good rebuild will be with fresh windings.+1
But, although the stator windings are replaced a lot, rotors and their windings rarely are in any rebuild shop. If the rear bearing surface is ok, the slip rings are trued up or replaced ant it's back on the street.
FWIW- Shops will have an excess of rotor and starter field windings but have a shortage of starter armatures and alternator field windings.
Big difference in their spin tests and load tests!

[iflights]

Had both of these symptoms. High pitched whine with engine off that only my son could hear (too much time for me as a roady), and a dead battery every 2 days.

Resorted to using my battery cut off switch for a year while I checked and/or replaced everything else...relays...fuses...door switches...glove box switches...hood switch...engine cover switch...replacement battery...everything.

Finally, for the price of a new alternator and simple installation my world changed and problem was solved. Purchased Alternator from PJ Grady.

[Patrick C]

Had both of these symptoms. High pitched whine with engine off that only my son could hear (too much time for me as a roady), and a dead battery every 2 days.

Resorted to using my battery cut off switch for a year while I checked and/or replaced everything else...relays...fuses...door switches...glove box switches...hood switch...engine cover switch...replacement battery...everything.

Finally, for the price of a new alternator and simple installation my world changed and problem was solved. Purchased Alternator from PJ Grady.

Good to know! If my whine reappears in the spring I will go this route as well.

[gluaisrothaii]

Pull the alternator and have it bench tested. Recheck the wiring to the alternator. As a stop-gap alternative you can install a battery master switch.

The alternator works perfectly- i.e. generates appropriate levels of smooth DC when running, and most of the time it shuts down when the ignition is turned off. A bench test will show it has zero issues. The problem is that it occasionally turns itself on, not every time.....DMCH already replaced it for me once. I'm sure they'll do it again.

[gluaisrothaii]

I was following this when it seemed to be resolved. Food for thought:
...



With the original alternators, the Brown wire is normally connected to AUX #2 Relay. Using the same terminal, it also feeds the BATT light via a Green wire through Fuse #5.
(! not 4, 6, 10 ???)

I'm suspecting PO mods e.g a radio's Always Hot Power/Memory wiring for the radip etc crossed up....Something feeding the regulator on a common circuit... Maybe see what happens if fuse #5 only is pulled.

(I'd jump the sense wire to the Main Alternator post, if not using the Brown wire even though all of the alternators I've seen so far with the feature have it virtually connected internally....)

FWIW-
Make sure the BATT bulb is correct. The wrong incandescent or a LED causes problems.

When you hear the sound, look VERY carefully at the BATT light for a faint glow.
If it does, the little diode trio/regulator in the alternator may be getting zapped...or defective Alternator #2.

All wiring is stock/original. It was an untouched car when I bought it. The alternator bulb is incandescent, as it should be. The alternator charges perfectly when the engine runs, stable smooth DC at 14.4/14.6 V. Just occasionally turns itself on when it shouldn't. I'll look at the bulb in the dark next time I hear the whine.

What I can say is that it takes very little voltage to activate the regulator. I was able to turn it on with .3Vdc. Seems like it should take more than that.

I guess this is why most aircraft use an externally regulated alternator with a split master switch which allows the alternator to be controlled independently of the main bus.

[gluaisrothaii]

A lot of rebuilders take short cuts. They may look for broken coating on the windings, pry apart what they can see and just re coat what it visible instead of actually rewinding the rotor.

A good rebuild will be with fresh windings.

It's a brand new CS130 from DMCH. Two in a row now.

[Ron]

It's a brand new CS130 from DMCH. Two in a row now. Pull it and take it to an auto parts that load tests (AutoZone does, around here anyway). It takes very little to pop the regulator or trio in those units (and several others). I can't count the times that customers reported problems immediately after simply giving someone a jump or using a cheap charger on their own vehicle in our rebuild shop...