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Odd one for you...
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=81030		 Page 1 of 1
Author:  greiswig [ Mon Jan 05, 2015 8:20 pm ]
Post subject:  Odd one for you...
Ever since replacing my cylinder head, FPS, and putting a Week's intake on, I am getting a high-pitched whine when I put my foot in it pretty hard. It's up around an A or A#, so I'm guessing...what, 3,520Hz or a little higher? Sounds electronic, doesn't vary with speed, may be coming from the speakers. With the amps on the speakers, you can turn the stereo off but still pick up RF at the speakers.

Any ideas?
Author:  ArmyChief [ Mon Jan 05, 2015 8:31 pm ]
Post subject:  Re: Odd one for you...
George,

I'm assuming you have the amplified Premium systems then. Have you tried to pull the fuse that powers the amps (or the relay/choke up under dash near accel pedal)?

Since the sound doesn't change with RPM, I would rule out Alternator. Was there a ground strap you may have forgot to install?
Author:  greiswig [ Mon Jan 05, 2015 8:52 pm ]
Post subject:  Re: Odd one for you...
(Smacks forehead). Didn't even think tolook for a separate fuse for the power amps. Good thinking!

Yeah, it isn't alternator whine. Too consistent in pitch. And the fact that it so reliably comes on at certain acceleration levels or above is also weird.

I'll see if I can find a fuse or relay and at least narrow down where it is coming from, but it's hard for me to imagine anywhere else it could be coming from. It just sounds electronic.
Author:  gmctd [ Mon Jan 05, 2015 10:09 pm ]
Post subject:  Re: Odd one for you...
Awhile back alternator technology improved greatly - instead of relying on increasing voltage with increasing frequency as rpm increased, pulse-width-modulation at specific frequency became the norm - alternator operation then resulted in greater charging capability at low rpm, plus less EMI\EFI\RFI interference in the super digital audio upgrades because of easier filtration for and of the single frequency

What you're hearing is likely result of poor grounding as mentioned earlier, or\and poor electrical connectivity
Author:  greiswig [ Mon Jan 05, 2015 10:36 pm ]
Post subject:  Re: Odd one for you...
gmctd wrote:
What you're hearing is likely result of poor grounding as mentioned earlier, or\and poor electrical connectivity


Why, though, would it only happen under load? And what is magic about 3600 Hz? I know what a signal with constant frequency but varying pulse width sounds like, and this is not varying the pulse width from what I can tell.
Author:  CATCRD [ Mon Jan 05, 2015 11:01 pm ]
Post subject:  Re: Odd one for you...
Sounds like a loose clamp on an intercooler hose or leaking intake gasket. Boost builds - air leaks.
Author:  gmctd [ Tue Jan 06, 2015 12:03 am ]
Post subject:  Re: Odd one for you...
Varying pulse width would be variation in volume, p'raps why you're hearing it:
- min charge, narrow pulse width = no sound
- greater than min charge, wider pulse width = sound

Less than 3600hz or so would be internal regulator operating frequency - seems like I remember something about not heterodyning with national power generation frequency at 60hz, or some such

It's all sorta foggy, right now, but I'll sit strait up in bed around 0230hrs, and it will be clear as a bell - and I'll need some warm milk to put me back to sleep

Make sure there's no oxidation between bolts and alt and brackets

Could also be as previous post, above ^^^^^^^^^^^^^^^^^^^^^^^^^
Author:  greiswig [ Tue Mar 10, 2015 3:24 pm ]
Post subject:  Re: Odd one for you...
Gonna bring this thread back up from the dead.

I tried unplugging the fuse for "Radio" on the driver's side of the dash. But it isn't clear to me that this also controls power to the power amp modules at the speakers. Does anyone know if that is the case? Because with the fuse unplugged, I am still getting this noise.
Author:  Billwill [ Wed Mar 11, 2015 6:35 am ]
Post subject:  Re: Odd one for you...
greiswig wrote:
Gonna bring this thread back up from the dead.

I tried unplugging the fuse for "Radio" on the driver's side of the dash. But it isn't clear to me that this also controls power to the power amp modules at the speakers. Does anyone know if that is the case? Because with the fuse unplugged, I am still getting this noise.


Looks to me from the circuit diagrams that Fuse 18 inside the cabin powers the radio and the amplifiers.

According to Keith from GDE and looking at the 2005 CRD circuit diagram....the alternator on the 2005 model has an internal regulator fitted and is not controlled by the ECM by PWM?

The output from fuse 18 goes through a "Radio Choke Relay coil" and then to the radio/speakers etc.
I have never heard of this "Radio Choke Relay" and do not know where it is located....once this relay gets energized by the voltage going through it to the Radio etc. the relay makes a contact which connects the Antenna Relay Output to ground but in any case pulling fuse 18 out should totally eliminate the sound system as your problem! :?
Author:  gmctd [ Wed Mar 11, 2015 1:40 pm ]
Post subject:  Re: Odd one for you...
The internal regulator is also PWM
- it's the most efficient method of widely varying the charging rates of a battery with continuous widely varying loading
- it's also the most difficult to troubleshoot and trace noises, as the PWM doesn't necessarily directly correspond to engine rpm
Author:  SFHLibertyCRD [ Wed Mar 11, 2015 7:36 pm ]
Post subject:  Re: Odd one for you...
Greiswig, nothing like the sound in my post that you commented on a while back? viewtopic.php?f=5&t=80642

Ended up being a not properly seated Samco for me.
Author:  Billwill [ Sat Mar 14, 2015 5:40 am ]
Post subject:  Re: Odd one for you...
gmctd wrote:
The internal regulator is also PWM
- it's the most efficient method of widely varying the charging rates of a battery with continuous widely varying loading
- it's also the most difficult to troubleshoot and trace noises, as the PWM doesn't necessarily directly correspond to engine rpm


Yeah I have always wondered if the Internal Regulator is also PWM...does make more sense on the newer design alternators. :)
Author:  WWDiesel [ Sat Mar 14, 2015 10:57 am ]
Post subject:  Re: Odd one for you...
Understanding PWM:
Simple definition of PWM I found,
PWM use technology similar to other modern high quality battery chargers. When battery voltage reaches the regulation setpoint, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the battery, yet the charging continues to return the maximum amount of energy to the battery in the shortest time. The result is a higher charging efficiency, rapid recharging, and a healthy battery at full capacity.

For an in-depth technical explanation of PWM, read and study this:
http://en.wikipedia.org/wiki/Pulse-width_modulation

Just curious if anyone might know; does the OBC communicate with the PWM regulator via a carrier signal to control the alternators output or is all control internal within the PWM regulator itself without any outside influences (OBC) other than system voltage? :roll:
Author:  gmctd [ Thu Mar 19, 2015 5:10 pm ]
Post subject:  Re: Odd one for you...
Actually, altho self-contained PWM regulators have been used for decades, it would appear that the KJ CRD alternator field is PWM-controlled at 100hz by the '05 FCM and the '06 BCM........................

So, no, the KJ CRD alternator is not a stand-alone enterprise
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