Fuba antenne fejlfinding
Old VW Antenne 3B0 035 505 New VW Antenne 1J0 035 505a
FUBA Antenna Troubleshooting:
By Samuel C.K. Lee
Do you have problems with radio reception? Don't be quick to blame your radio just yet. The problem may lie with the radio antenna.
Unbeknownst to most, the OEM factory "whip" style antenna is an amplified system. Manufactured by FUBA Communications of Germany, the OEM antenna, the Beta-flex D, is an active antenna that employs separate amplifier circuits for the AM and FM bands. These circuits are designed to boost the most radio signals possible while filtering out unwanted stations and noise. These microelectronic circuits are housed in the antenna's base while the receiving element consists of a spring loaded, wire-wound, fiberglass mast designed to withstand most automatic carwash machinery.
The mast is removable or can be locked on with glue.
Symptoms of problems with radio reception include poor FM reception (only strong stations tune in), and virtually no AM reception.
Other indications of faulty antenna operation include audible "pops" heard on the AM band originating from turn signal or windshield wiper relays.
The culprit to these problems may be that the antenna is not getting 12 volt power, the antenna is poorly grounded, or the antenna amplifier may be bad. The worst case scenario is that neither of these problems is the cause and the radio itself is bad. If you have an aftermarket radio, the antenna may not be receiving power or you may have an ill-fitting antenna RF cable adaptor. Regardless, to troubleshoot for the source of the cause will require gaining access to the antenna and power connections at the back of the radio and at the base of the antenna.
Accessing the Radio Connections
- The Aktiv and Premium Sound head units have common mounting hardware. The vertical pairs of holes on either side of the unit are the access sites to unlatch the securing mechanism. U- shaped adaptors are available at the dealer or aftermarket car stereo stores, but are generally unnecessary. U-shaped pieces can be easily fabricated from thick wire coat hangers. Simply cut a coat hanger with wire cutters and bend two pieces into an U-shape. Insert the ends into the vertical pairs of holes and manipulate the latches until the unit can be easily pulled forward. Gentle lateral pressure at the bent ends of the U is generally sufficient to unlatch the mechanism so that the radio can be pulled out.
If you have an aftermarket unit, refer to the owner's manual for proper removal procedures. The antenna RF cable is a thick black cable that connects to the right side of the unit (front as reference). The antenna remote power-on lead that supplies 12 volt power is a black wire coming from pin 5 (marked with an antenna symbol that resembles a "Y" with an additional vertical line) of the wiring harness that carries the power leads. The connector for this harness is black and has a key tab that is offset and not centered.
Accessing the Antenna Amplifier Connections
Power connections at the base of the antenna require partial disassembly of the head liner. With the hatchback open, sit in the rear seat and carefully remove the plastic trim at the edge of the liner adjacent to the open part of the hatch. There are approximately 6-7 tabs that hold this piece in place. You may have to loosen the C-pillar trim on either side to make removal easier. Once the trim is removed, the head liner may be bent carefully to access the antenna leads and the mounting nut for the unit itself. Power and RF leads extend from the antenna amplifier unit through the mounting nut and connect with the power and RF cable that extends from the head unit in front of the car.
Check for obvious corrosion or loose connections at the head unit and at the antenna amplifier. If you have an aftermarket head unit, check to make sure the antenna power lead is connected to remote power-on.
Additionally, VW uses a DIN-3 RF cable connector which may require an adaptor to connect with an aftermarket unit. If an adaptor is used, make sure it fits properly and that the connection is secure.
With the power off, use an Ohmmeter to make sure the contact nut is grounded to the chassis. Continuity check (i.e., test for a short circuit) the contact nut against a known chassis ground. You should read minimal resistance (Ohms) or if your meter has a continuity setting, you should hear an audible tone. Otherwise, loosen the nut, clean any corrosion, retighten and recheck continuity.
Use a voltmeter or test light to make sure the antenna is receiving 12 volts. Disconnect the power lead at the antenna. With the unit on, test for 12 volts between the power lead and the contact nut under the antenna.
You should read 12 volts on the meter or the test light should light up.
I not, check the power connections at the head unit. In addition, use the volmeter to verify that the remote power-on is putting out 12 volts at the head unit.
If 12 volt power is verified, check RF cable continuity. Continuity check both the center lead and the ground (the outer metal portion, i.e., the shield) of the RF cable separately. That is, check the center lead of one end of the cable to the center lead of the other end of the cable. Test the ground in a similar manner by checking the shields at both ends of the cable. To test for a short circuit between the RF cable center lead and ground, check the center lead against the shield at either end of the cable. If the center lead or ground lack continuity, or if there is a short between the center lead and the shield, then the RF cable is damaged and may be crushed or crimped cable along the route to the radio. Verify continuity with the shield and chassis ground. If there is no continuity, then the RF cable is not connected to ground.
Lastly, test the car radio itself for proper operation with a standard rod antenna on a short cable. Ground the antenna if possible. Another quick and dirty test is to pull the radio and plug it into another VW with either an amplified antenna or standard antenna. The power and speaker wiring harnesses are similar across VWs. I was able to test my radio in a VW Fox with a standard antenna.
If the radio lacks a power antenna lead, connect the power lead from the antenna to the accessory side of the fuse block, or tap into the power line going to the radio if it is switched by the ignition/accessory position. The amplifiers in the antenna draw approximately 30 mA which can drain a battery if left on for extended periods while the car is parked. To minimize RF noise, avoid running the RF cable along or next to high-current-draw cable such as power leads for amplifiers, etc.
If the radio checks out and all ground and power connections are good, then the antenna amplifier unit needs to be replaced. The FUBA unit retails for around $120-$130 at the local VW dealer. The OEM FUBA is available through aftermarket dealers such as New Dimensions, ABD, Rapid Parts, Euro Sport for around $55-$65. Note that the OEM FUBA has a different mounting post than the factory unit. The OEM unit has a round flange where as the factory unit has a square flange that prevents rotation. Also note that both amplified and non-amplified OEM units are available so make sure you order the correct FUBA unit. Mounting instructions are included with the unit and are fairly straightforward and easy to follow.
To minimize potential damage to the antenna amplifier, turn off the radio and thus the power to the antenna when working with electrical connections to the car. This includes the instances when the car is taken in for service. When removing the antenna mast, again turn off the power first. I am unable to comment if the antenna amplifiers are designed to operate without the resistive load that the mast provides, so as a preventive measure, do not operate the stereo without the mast in place.