vwestlife
Veteran Member
When I first got my '97 Passat TDI, it came with an aftermarket AM/FM/CD radio which did not have the correct antenna adapter to feed +12V power to the antenna's amplifier. Needless to say, FM reception was poor, and AM reception was completely non-existent.
I replaced that radio with a Clarion OEM "Premium Audio" radio that was originally in my sister's '96 Golf. I previously had this radio in my '91 Golf (with the regular fender-mount antenna) and it had perfect reception on both AM and FM, so I know it's a good radio. With this radio installed, I can tell the amplified antenna is working, as FM reception is about as good as I would expect and I can actually get reception on AM, not just blank channels.
But, its reception of weaker AM signals is marred by a constant loud hiss, and especially towards the higher end of the band, there is a constant "computer whine" -- the same kind of noise you get if you place an AM radio too close to a computer that's on (or, really anything with a microprocessor in it -- VCRs, fax machines, printers, etc. can all make this "computer whine" on AM radio).
The first thing I noticed is that in the Passat, the metal case of the radio is not grounded, as all it touches inside the dash is plastic. So, I took a piece of wire and connected the radio's case to a metal frame bar inside the dash. This reduced the AM radio static by a noticeable amount, but it's still there, strong enough to drown out reception of weaker signals.
Since that "computer whine" definitely sounds like it's coming from something with a microprocessor in it, I thought the car's ECM might be the cause. I pulled the fuse marked "Engine Electronics" -- no change! So, I pulled all the other fuses to try to track down the cause of the interference. None of them eliminated it completely, but I did notice the "computer whine" reduced quite a bit when I pulled the "clock" fuse (which made the instrument cluster go blank). And in other experimentation, the noise is also reduced a lot when I turn on the headlight switch, which lights up the instrument cluster's backlighting.
In my next round of troubleshooting, I unhooked the radio from the car's DC supply and powered it with a seperate gel-cell 12-volt battery. This did not cause any noticeable change, so I disconnected the car's antenna and used a piece of wire as a makeshift antenna. While this reduced the noise on AM, it also reduced the reception of even strong AM signals, as the wire doesn't have the correct length and position to serve as an effective car radio antenna.
So given this evidence, can anyone help me track down the source of this annoying AM noise/static? I know the radio itself isn't causing it, because I held the wire antenna right up to the radio's LCD display and it make a completely different-sounding kind of interference than what I've been hearing constantly.
Could the anti-theft alarm system be causing this interference? It looks like the alarm system is non-fused and is powered whenever the car battery is connected, so if it's the cause, that would explain why the noise never went away completely when I pulled all the fuses. I also have noticed that unlike my sister's '96 Golf and my dad's 2002 Golf, my Passat does not beep the horn when the alarm is armed, and I don't ever see it flash the parking lights when it is armed or disarmed. The only indication I have that the alarm is doing anything is the red blinking light in the driver's door, which does go on when the car is locked. (But this may be normal for a B4, as the owner's manual doesn't make any mention of beeping or lights flashing during arm/disarm.)
So if there any easy way to completely disconnect the alarm system, so that its "brain" (wherever that may be) doesn't receive any power? Of course, I can just disconnect the car's battery, but then the car would be undrivable. If the alarm system really is the cause of all this AM radio noise, then I can easily live without it, as it's virtually worthless anyway -- the wimpy "meep... meep... meep" of a VW alarm barely even scares away my cat, let alone a potential thief!
This is rather annoying because one of the smaller reasons why I chose a diesel is that it won't have the "AM buzz/crackle" caused by the ingition system in all the gas-engine VWs I've owned... but instead of that, I get AM radio static that is even worse, even with the engine turned off!
I replaced that radio with a Clarion OEM "Premium Audio" radio that was originally in my sister's '96 Golf. I previously had this radio in my '91 Golf (with the regular fender-mount antenna) and it had perfect reception on both AM and FM, so I know it's a good radio. With this radio installed, I can tell the amplified antenna is working, as FM reception is about as good as I would expect and I can actually get reception on AM, not just blank channels.
But, its reception of weaker AM signals is marred by a constant loud hiss, and especially towards the higher end of the band, there is a constant "computer whine" -- the same kind of noise you get if you place an AM radio too close to a computer that's on (or, really anything with a microprocessor in it -- VCRs, fax machines, printers, etc. can all make this "computer whine" on AM radio).
The first thing I noticed is that in the Passat, the metal case of the radio is not grounded, as all it touches inside the dash is plastic. So, I took a piece of wire and connected the radio's case to a metal frame bar inside the dash. This reduced the AM radio static by a noticeable amount, but it's still there, strong enough to drown out reception of weaker signals.
Since that "computer whine" definitely sounds like it's coming from something with a microprocessor in it, I thought the car's ECM might be the cause. I pulled the fuse marked "Engine Electronics" -- no change! So, I pulled all the other fuses to try to track down the cause of the interference. None of them eliminated it completely, but I did notice the "computer whine" reduced quite a bit when I pulled the "clock" fuse (which made the instrument cluster go blank). And in other experimentation, the noise is also reduced a lot when I turn on the headlight switch, which lights up the instrument cluster's backlighting.
In my next round of troubleshooting, I unhooked the radio from the car's DC supply and powered it with a seperate gel-cell 12-volt battery. This did not cause any noticeable change, so I disconnected the car's antenna and used a piece of wire as a makeshift antenna. While this reduced the noise on AM, it also reduced the reception of even strong AM signals, as the wire doesn't have the correct length and position to serve as an effective car radio antenna.
So given this evidence, can anyone help me track down the source of this annoying AM noise/static? I know the radio itself isn't causing it, because I held the wire antenna right up to the radio's LCD display and it make a completely different-sounding kind of interference than what I've been hearing constantly.
Could the anti-theft alarm system be causing this interference? It looks like the alarm system is non-fused and is powered whenever the car battery is connected, so if it's the cause, that would explain why the noise never went away completely when I pulled all the fuses. I also have noticed that unlike my sister's '96 Golf and my dad's 2002 Golf, my Passat does not beep the horn when the alarm is armed, and I don't ever see it flash the parking lights when it is armed or disarmed. The only indication I have that the alarm is doing anything is the red blinking light in the driver's door, which does go on when the car is locked. (But this may be normal for a B4, as the owner's manual doesn't make any mention of beeping or lights flashing during arm/disarm.)
So if there any easy way to completely disconnect the alarm system, so that its "brain" (wherever that may be) doesn't receive any power? Of course, I can just disconnect the car's battery, but then the car would be undrivable. If the alarm system really is the cause of all this AM radio noise, then I can easily live without it, as it's virtually worthless anyway -- the wimpy "meep... meep... meep" of a VW alarm barely even scares away my cat, let alone a potential thief!
This is rather annoying because one of the smaller reasons why I chose a diesel is that it won't have the "AM buzz/crackle" caused by the ingition system in all the gas-engine VWs I've owned... but instead of that, I get AM radio static that is even worse, even with the engine turned off!
