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-   -   NAS 110 Whine with ICOM Turned On (http://www.expeditionexchange.com/forums/showthread.php?t=1221)

RKurk September 3rd, 2008 12:32 PM

NAS 110 Whine with ICOM Turned On
I have a strange sound from my NAS 1993 110 when I have my ICOM 208H radio turned on (in receive mode) I get a very noticeable medium to high pitch whine from the engine bay. The pitch changes as the engine speed increases, most notably from idle to about 1500 rpm. The whine occurs only when the ICOM is powered on. I have had the alternator and charging system checked and everything tested fine. The radio is connected directly to the terminal on the battery (positive) and after the battery shutoff switch (negative). The radio is mounted on the front facing ‘slope’ of a Tuffy center console. The power wires for the ICOM run from the battery compartment and up through the access cover over the transfer case (the stock routing of the wiring for the AM/FM radio). The antenna coax runs through the interior under the carpet. Finally, the whine disappeared for about two months and then returned for no apparent reason.

Any ideas or suggestions regarding what is causing this?


Richard Kurk

greghirst September 3rd, 2008 01:31 PM

You said you had your alternator checked? Did they check ground connections too? Check radio grounding as well.

Not sure what the amp draw is for the ICOM but perhaps the additional draw is causing a worn alternator bearing or belt tensioner bearing to whine?

RKurk September 4th, 2008 12:29 PM

Greg, I had the alternator checked early on with the problem. The whining sound was very (frightenly) similar to a problem I had years ago with a Chevy van. The van use to go through an alternator every 25k miles do to some unknown problem. When it would start to go bad there was a whine that would increase or decrease with engine speed. Every indication is the 110 alternator and general charging is fine.

I believe the ICOM draws very little when in receive mode (vs. transmit) and the whine seems ICOM related because I can turn on a lot of other items (fog lights, AC, even the winch) and not get the whine.

I think I may remove the ICOM from the center console and physically relocate it temporarily somewhere else and see if something changes (I know ... this is really reaching for a cure).

Just to make sure I will re-check the radio power connections (ground and positive).

One more thought ... I have a ICOM V8000 in my Discovery, maybe I will connect that up and see if the whine continues.

Thanks for the comments.

ronward September 4th, 2008 12:41 PM

A long shot, but you are certain the sound is coming from the engine and not a speaker up in the dash? My NAS 110 (No. 200/500) had an aftermarket stereo head unit and a it was connected up through an additional speaker in the lower dash that was also used with a CB radio. I got a hell of a noise sometimes when the stereo was on but the CB off through that speaker and I thought for days it was the alternator. Just my $0.02 worth...

ROVERM205 September 4th, 2008 08:19 PM

Check out WWW.k0Bg.COM there is a very good noise identification section check it out

RKurk September 8th, 2008 12:19 PM

A quick update. Yesterday I stuck my head down near the floor while my son adjusted the throttle up and down. The sound is not coming from the engine bay, but from the ICOM speaker. Because of the location of the ICOM the sound is reflecting off the Tuffy box and then the floor and it fooled me into thinking it was from the engine. I disconnected the antenna from the back of the ICOM but no change. Unfortunately as soon as I moved the Defender into the garage to continue the search for the source of the problem the sound went away again (which it does regularly to torment me!).

David, I will check out the link this evening.

Something is generating interference, I just need to find it.

Thanks for the help.

Maryland 110 September 28th, 2008 05:08 AM

Had a simliar problem with the ICOM VHF on my Bertram sportfish. Turned out to be a bad gound.

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