Expert: Cleggsan - 5/14/2011

Question
QUESTION: I have a 1999 VW Jetta, a late 1999, the newer body style.  The radio works very well on FM and it does work on AM, but the signal reception is poor.  I get a lot of static and in the background you can hear the station.  Ideas?  Is there an antenna trimmer adjustment on the radio itself that would help?  Could it be the antenna itself?  Thanks!

Jon

ANSWER: It is generally caused by a bad ground connection on the antenna.  You can check the ground system; either it is the antenna itself that is mounted to the metal of the car or a separate ground wire that comes out the bottom of the antenna and is separately grounded.  The ground connection will sometimes get corroded or rusty and needs regrounded for a good solid ohmic connection.

Yes, it could be a defective antenna, but check the grounding first.  Also, the cable going from the antenna to the radio can be defective but I ruled that out because you reported good fm reception.

Hope this helps.



---------- FOLLOW-UP ----------

QUESTION: Thanks very much for your timely reply.  I do have one more question for you.  Is there a good way of checking the ground connection at the antenna itself without taking out the headliner?  From what you describe I would need to check the ground connection of the antenna itself from underneath the antenna - above the headliner and below the metal roof.

Am I on the right track?  Any ideas?

Again - thank you VERY much for you reply and your help!

Jon

Answer
It can be checked with an ohmmeter but it must be an meter capable of measuring very low resistance levels; of the order of much less than one ohm.  

It is rather advisable to just re-install the grounds making sure they are good.  Often it requires removing the ground,  sanding down the surface where the ground connection is made and buff it with steel wool and mount the antenna down again.  That is the only way of getting a good ground.  Most of the time  a bad ground has been caused by water/moisture getting into the area where the ground connections are.

Good Luck.

PS:  Sometimes you can determine if the antenna or its ground is the problem by manually jiggling the antenna and the cable while the radio is on.  Doing so may indicate the connections are restoring to normal operation with the vigorous jiggling of the antenna parts.