Terrible radio reception in 993?
01-30-2014, 04:27 PM
#31
Racer
Join Date: Jul 2009
Posts: 331
Likes: 0
Received 0 Likes
on
0 Posts
My '95 Carrera has adequate FM reception, but zero AM reception; literally nothing even parked next to the radio broadcast station! Based on this thread, guess a wiring investigation is in my future.
Original windshield, possible (probable) dash removal (to fix non-functional speedometer) prior to my caretakership.
Original windshield, possible (probable) dash removal (to fix non-functional speedometer) prior to my caretakership.
02-03-2014, 03:03 PM
#33
Rennlist Member
Join Date: Jan 2012
Location: NH.
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
(to fix non-functional speedometer)
04-03-2014, 07:16 PM
#34
Rennlist Member
Join Date: Jan 2012
Location: NH.
Posts: 13
Likes: 0
Received 0 Likes
on
0 Posts
I believe the easiest way to replace the antenna amp is to remove the dash, which ended up being way easier than I expected. One word of caution, is to pull the dash from front to back, not in the upward position. The stud behind the clock will tear out if pulled up. When all was said and done and wired correctly, I now have a working radio.
09-09-2014, 06:24 PM
#35
Track Day
Join Date: Oct 2003
Location: Cato Wisconsin
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
okay I have had similar degrading radio issues. I also own a stereo store and have been trying to address this issue for over 30 hours now. I have replaced the antenna booster which is located in the right front fender accessed from the boot. no improvement. I have tried several radio i have tried shielding the antenna lead. and even tried different antennas.... all with crappy results. Connected the radio to a different power source (different battery) and radio reception was awesome.... turned the vehicle key on to accy and the radio reception was gone! its not a powere issue and the antenna was in my hand not attached to the car windshield antenna. Then a funny thing happened... I stood up and moved the antenna away from the car and when it was 3' from the car all was good again! move the antenna closer to car and reception degrades.
I have deduced while I have absolutely no ignition noise or alternator whine on any sources and the CD USB Streaming audio all are clear as a bell the problem exists with FM reception. Or what is emitting RF interference in the vehicle electronics blocking the weaker radio reception! Some electronic component in the vehicle probably has failed, or has a failed part in it creating RF interference the antenna in close proximity to the vehicle is picking up.
I have discussed this in my own stereo shop, talked to other two way communication shops and they all agree... but no one knows how to locate this. How does one figure out what is emitting the RF thats blocking the radio reception?
It would be awesome to locate this item and thus fix the problem.
Oh and id like to add I have located all 16 grounds cleaned them and regrounded them. the problem only happens when vehicle is turned on or running. Obviously when all properly connected the vehicle has to be turned on to listen to the radio but the problem does not lie within the radio or the antenna its what is emitting a signal thats blocking the radio signal which is weaker.
HELP all thoughts are appreciated!
Cannonball
I have deduced while I have absolutely no ignition noise or alternator whine on any sources and the CD USB Streaming audio all are clear as a bell the problem exists with FM reception. Or what is emitting RF interference in the vehicle electronics blocking the weaker radio reception! Some electronic component in the vehicle probably has failed, or has a failed part in it creating RF interference the antenna in close proximity to the vehicle is picking up.
I have discussed this in my own stereo shop, talked to other two way communication shops and they all agree... but no one knows how to locate this. How does one figure out what is emitting the RF thats blocking the radio reception?
It would be awesome to locate this item and thus fix the problem.
Oh and id like to add I have located all 16 grounds cleaned them and regrounded them. the problem only happens when vehicle is turned on or running. Obviously when all properly connected the vehicle has to be turned on to listen to the radio but the problem does not lie within the radio or the antenna its what is emitting a signal thats blocking the radio signal which is weaker.
HELP all thoughts are appreciated!
Cannonball
09-09-2014, 07:40 PM
#36
Rennlist Member
Frustrating problem!
Sounds like you may have a broken or loose connection where the antenna wire (that plugs into the amplifier)attaches to the windshield.
I recently replaced my amplifier by removing the dash cover and if you got it thru the boot
you must have some small hands or someone at your shop does. It may be possible whoever removed the amplifier didn't realize there are 3 wires attached to it, and gave it a gentle tug disconnecting the windshield connection. I'd start there first.
Sounds like you may have a broken or loose connection where the antenna wire (that plugs into the amplifier)attaches to the windshield.
I recently replaced my amplifier by removing the dash cover and if you got it thru the boot
you must have some small hands or someone at your shop does. It may be possible whoever removed the amplifier didn't realize there are 3 wires attached to it, and gave it a gentle tug disconnecting the windshield connection. I'd start there first.
09-09-2014, 08:34 PM
#38
Nordschleife Master
Does the reception gradually diminish as the antenna is moved towards the vehicle or does it go from good to bad suddenly?
It seems very unlikely that there is a noise source strong enough to jam across the radio spectrum (does it occur for both AM and FM?)
My guess is a damaged wire, that is losing contact or weakened contact as you move the antenna.
I guess the other thing I would try is to locate a portable transistor am/fm radio and move it around the car and see if it too loses reception, possibly you can move it around to locate the "source"
It seems very unlikely that there is a noise source strong enough to jam across the radio spectrum (does it occur for both AM and FM?)
My guess is a damaged wire, that is losing contact or weakened contact as you move the antenna.
I guess the other thing I would try is to locate a portable transistor am/fm radio and move it around the car and see if it too loses reception, possibly you can move it around to locate the "source"
09-18-2014, 02:23 AM
#39
Track Day
Join Date: Oct 2003
Location: Cato Wisconsin
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
Okay I have isolated where the interference is! It is emanating from the power window circuit! Pulled the power window fuse and all radio reception returned. So I dug into this further starting at driver door... Pulled driver door switch for passenger window with the power window fuse back in and the interference stops as well... Put door switch back in circuit and interference is back. Pulled passenger side switch and interference still there.
The power window circuit is a direct five wire polarity reversing circuit between driver door switch and passenger switch for the passenger window the driver door switch feeds power to the passenger switch. When at rest the power wire feeding the passenger side is creating rf noise. When circuit is open only or switches are rest.
I suspect the traveler power wire in the dash is routed user the top of radio in dash and antenna wires. Moving the antenna antenna away from the dash resolved the interference while moving it closer increased it.
My next step it to locate the traveler wire and rewire it and relocate it away from dash. It would make sense that while everyone who has had this problem has not resolved it because it is not an antenna issue in those cases and perhaps others as well. I will post up more as I get further into this.
Just a little more info I am a 40 year stereo installer and my tech is a 20 year installer as well....we both have worked on this issue for over 30 hours and finally figure the oe wire location of the harness may either be degrading signal in some vehicles because not all harnesses are laid in exactly the same or the way wires are twisted in the harness. Either way I'll know more by end of weekend!
The power window circuit is a direct five wire polarity reversing circuit between driver door switch and passenger switch for the passenger window the driver door switch feeds power to the passenger switch. When at rest the power wire feeding the passenger side is creating rf noise. When circuit is open only or switches are rest.
I suspect the traveler power wire in the dash is routed user the top of radio in dash and antenna wires. Moving the antenna antenna away from the dash resolved the interference while moving it closer increased it.
My next step it to locate the traveler wire and rewire it and relocate it away from dash. It would make sense that while everyone who has had this problem has not resolved it because it is not an antenna issue in those cases and perhaps others as well. I will post up more as I get further into this.
Just a little more info I am a 40 year stereo installer and my tech is a 20 year installer as well....we both have worked on this issue for over 30 hours and finally figure the oe wire location of the harness may either be degrading signal in some vehicles because not all harnesses are laid in exactly the same or the way wires are twisted in the harness. Either way I'll know more by end of weekend!
Last edited by Cannonball; 09-18-2014 at 04:58 PM. Reason: typos
09-18-2014, 04:59 PM
#41
Track Day
Join Date: Oct 2003
Location: Cato Wisconsin
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
Allen while I agree the music is nice out side the car sometimes I like to listen to it inside the car as well... this issue has been bothering me for the last five years. I have to get to the bottom of it once and for all because Porsche dealer is no help.
09-20-2014, 02:03 AM
#43
Track Day
Join Date: Oct 2003
Location: Cato Wisconsin
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
Radio reception is fixed! After looking at the schematic further there are two power wires that deliver 12 volt between the driver door switch and the passenger door switch. Disconnected these two wires at the kick from the door harness connecter and ran two new wires between the two kick harnesses door connectors and re routed them at floor level under mat along existing other wire harnesses. No more rf interference and radio reception is awesome again. So it was nothing to do with the antenna booster, the power connection for the booster or the connection at the windshield at all! The antenna works fine the radio signal was being over powered with the RFI created by the power wires for the windows in the factory wire harness run over the radio in the dash. Re moving them from the circuit and replacing them and re routing the new wires away from the radio and antenna wire removed the interference. All is good. So people who have radio reception issues need to look sometimes at things other than the antenna! I could do this fix on another one in about two hours now it's easy!
09-20-2014, 11:34 AM
#44
Rennlist Member
That's fantastic congrats on the fix. To spend those kind of hours to fix a small problem is however, a sickness. A sickness nonetheless that I and others here share 
nothing like fixing something.
A couple questions for future readers. Which antenna booster did you replace with? Oem or aftermarket? (could have different shielding properties) You said you went in from the trunk, right? So how did you route the wire to the radio? Under dash? Fair disclosure here, I replaced my booster by removing the dash cover and wrote it up if anyone wants to search, and the wire runs by itself thru a sneaky little route thru three clips close to no other wires. I'm only guessing here since you didn't remove the dash, but is it possible you placed the new booster wire near the window wire contributing to the interference since you didn't remove the dash? An ugly question I concede just trying to help future readers if this was the case. Regardless, nice work getting it resolved.
nothing like fixing something. A couple questions for future readers. Which antenna booster did you replace with? Oem or aftermarket? (could have different shielding properties) You said you went in from the trunk, right? So how did you route the wire to the radio? Under dash? Fair disclosure here, I replaced my booster by removing the dash cover and wrote it up if anyone wants to search, and the wire runs by itself thru a sneaky little route thru three clips close to no other wires. I'm only guessing here since you didn't remove the dash, but is it possible you placed the new booster wire near the window wire contributing to the interference since you didn't remove the dash? An ugly question I concede just trying to help future readers if this was the case. Regardless, nice work getting it resolved.
09-20-2014, 03:08 PM
#45
Track Day
Join Date: Oct 2003
Location: Cato Wisconsin
Posts: 17
Likes: 0
Received 0 Likes
on
0 Posts
Okay Fair Disclosure first of all I have a 993 TT. I have a Fuse box, fuel tank and a lot of stuff crammed in the boot at the cowl.My booster is in the right fender under the and behind the hood hinge and strut. Hood removed to replace it. the duct work in the cowl must come out and wire routing is exactly as OEM. I replaced it with the OE unit and then later an aftermarket unit in attempts to resolve the issue. even thought about adding a roof top antenna. this is when I noticed the RFI problem as I was moving an external antenna around. The wire routing is exactly the same as factory in factory clips. i pulled the entire glove box out and am able to access everything from there and the radio opening.Pulling the dash top or entire dash is unnecessary.
Shielding??? Well coax cable is shielded in both OEM and Aftermarket. the signal actually is conducted on the teflon and bounced between the inner and outer conductors. None of these were broken either. I even went as far as to add an additional outer copper braid shield grounded and tried it grounded at one and both ends too which didnt help and the antenna cable is routed next to the OEM harnesses in the dash. as the antenna cable was pulled back and into the cockpit RFI decreased. this is when I realized the antenna was not the issue something else was. I pulled fuses one by one until I found pulling the door lock fuse stopped the interference. The interference isnt limited to my vehicle there are lots of posts with it and antenna replacements and booster replacements dont seem to help people.
The process in which we tested and isolated allowed us to track where the RFI was coming from and it was not door motors or switches.. but only the wire in between. Now I dont know if in the factory harness there is a cap or ground point mid dash or not but the schematics do not show one. wires in different harnesses do get twisted differently I can only assume that the two cross over power window switch wires between the driver door passenger side switch and the passenger door switch in my car are twisted just right to create an RFI antenna that because of the close proximity to the radio antenna wire and windshield antenna was stronger than the broadcast signal being received from the radio stations and in essence was blocking or jamming them because it was closer and stronger. Pay special attention as the US wiring is different from the Euro wiring for this circuit.
40 years in the stereo business had only had one other car ever give me issues like this. and on that car I had to lift and isolate the entire dash from the vehicle sheet metal attachment points because it was doing the same thing. I just forgot my basics when I started and ASSUMED it was an antenna problem and until I tried another antenna away from the car body and dash I would have kept assuming this was the issue because there was absolutely no noise in the system typically associated with ignition or alternator noise..
Keep asking questions and Ill answer because a car that sounds good on the outside should sound good on the inside as well!
CB
Shielding??? Well coax cable is shielded in both OEM and Aftermarket. the signal actually is conducted on the teflon and bounced between the inner and outer conductors. None of these were broken either. I even went as far as to add an additional outer copper braid shield grounded and tried it grounded at one and both ends too which didnt help and the antenna cable is routed next to the OEM harnesses in the dash. as the antenna cable was pulled back and into the cockpit RFI decreased. this is when I realized the antenna was not the issue something else was. I pulled fuses one by one until I found pulling the door lock fuse stopped the interference. The interference isnt limited to my vehicle there are lots of posts with it and antenna replacements and booster replacements dont seem to help people.
The process in which we tested and isolated allowed us to track where the RFI was coming from and it was not door motors or switches.. but only the wire in between. Now I dont know if in the factory harness there is a cap or ground point mid dash or not but the schematics do not show one. wires in different harnesses do get twisted differently I can only assume that the two cross over power window switch wires between the driver door passenger side switch and the passenger door switch in my car are twisted just right to create an RFI antenna that because of the close proximity to the radio antenna wire and windshield antenna was stronger than the broadcast signal being received from the radio stations and in essence was blocking or jamming them because it was closer and stronger. Pay special attention as the US wiring is different from the Euro wiring for this circuit.
40 years in the stereo business had only had one other car ever give me issues like this. and on that car I had to lift and isolate the entire dash from the vehicle sheet metal attachment points because it was doing the same thing. I just forgot my basics when I started and ASSUMED it was an antenna problem and until I tried another antenna away from the car body and dash I would have kept assuming this was the issue because there was absolutely no noise in the system typically associated with ignition or alternator noise..
Keep asking questions and Ill answer because a car that sounds good on the outside should sound good on the inside as well!
CB