So my son's 87 GT auto has a high pitch whine coming from inside the cabin (right side front). It changes with accelaration/deceleration. I have shut off the radio and the hvac and it doesn't change. I'm at a loss as to what could be causing it.
Inside the cabin Id say pull the radio fuse and see if it stops, you did say you turned it off tho. Or Blue dingy thingy?
Radio feedback can still find its way into the speakers even when the fuse is pulled, if the radio waves are converted to electrical energy within the speaker wires.
First thing to do is to isolate where exactly the sound is coming from (if it's from a speaker, center console, etc…). If you are hearing a change in pitch that matches a change in RPM though, then it's almost certainly RF interference being picked up in the radio/speakers. Check all the ground straps for the engine, and the strap for the RF shield that's in the decklid.
Well I just had a chance to look at it, I pulled the blue dingy thingy and no change. The ground strap looks good, but the one on the right side that goes from the hinge to the clip on the deck lid is broke and frayed. I went around the inside and outside (front) with a mechanics stethoscope and was unable to pin point exactly where it's coming from. I'm going to see about fixing that one ground strap as I thought I heard it's point was to decrease radio interference.
Where is the tach filter and how do I change it? (i'm so not a mechanic but willing to learn )
Thanks,
Dan
[This message has been edited by DanFiero (edited 01-29-2015).]
Well I just had a chance to look at it, I pulled the blue dingy thingy and now change. The ground strap looks good, but the one on the right side that goes from the hinge to the clip on the deck lid is broke and frayed. I went around the inside and outside (front) with a mechanics stethoscope and was unable to pin point exactly where it's coming from. I'm going to see about fixing that one ground strap as I thought I heard it's point was to decrease radio interference.
Where is the tach filter and how do I change it? (i'm so not a mechanic but willing to learn Dan
You can just loosen the bolt, unplug and replace with a new one. Rodney sells them. You can maybe disassemble and repair as well if you have some basic wiring and electronics skills. http://www.fieros.de/en/articles/tachfilt.html is a pretty good write-up on diagnosing it.
The ground strap looks good, but the one on the right side that goes from the hinge to the clip on the deck lid is broke and frayed. I'm going to see about fixing that one ground strap as I thought I heard it's point was to decrease radio interference.
Radio have capacitors that dries out over 20+ years and stops working. Is a big cap that filters main power on the big connector will let alt whine when radio is on, especially on AM channels.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Well, I added another ground strap and tried to repair the one that was frayed. I also removed the radio and replaced it with another Fiero radio. No change in the whine . May have to try the tach filter.
O.K., so changed radio with another stock radio, no luck...pulled the blue box..no luck....added another ground strap...no luck, and now I have changed the alternator (which was failing any way and my best bet for a cure) and........no luck Running out of ideas other than the tach filter which I may try next.
Yes we can here it sitting in the driveway. If we rev the engine the pitch does change but not necessarily in tune with the engine if that makes any sense.
edit: my son just informed me that it seems worse when it's cold out. "it seems to go away when it's nice out or the car is warm"
interesting....now if it would just get above zero to test this theory.
[This message has been edited by DanFiero (edited 02-27-2015).]
Originally posted by DanFiero: Yes we can here it sitting in the driveway. If we rev the engine the pitch does change but not necessarily in tune with the engine if that makes any sense.
edit: my son just informed me that it seems worse when it's cold out. "it seems to go away when it's nice out or the car is warm"
interesting....now if it would just get above zero to test this theory.
That sounds more like a belt.
Also, I noticed that if the PCV tube is not seated in the intake tube 100% correctly, it can result in air being sucked in next to the PCV tube through the intake, and when you rev the engine, this can produce a slight "squeal" sound, due to the air passing over the rubber. It is high pitched and will happen when you step on the gas. It's not a constant noise though, only something that happens or is noticeable when the go pedal is pressed.
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. May have to try the tach filter.
