What is the deal with my radio 99 Jetta TDI GLS New Body Style

The factory antenna needs power which is supplied by a factory radio. An aftermarket radio can be used with an adapter that injects this power into the coax.

Should of done the ant cable first! Looks doesn't mean the cable is good... how did you check it?

It works fine with FM. If I disconnect the antenna from the new radio I get nothing, connected gets FM only really well, and occassionally some AM.

Is that true for FM and AM? I had it done by Circuit City. I know they aren't a VW dealer, but they should have known about the power injection.

So, I may just need an adapter for the aftermarket radio. Is that a VW part or a aftermarket part? What exactly would it be called?

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OK, so I found out that Circuit City actually did the job correctly using the proper wiring harness and the power injection is properly working but AM is not. :-(

Well, I got the new cable today and I am going to try it without running it first. Is it lookse enough in the headliner to pull through by pulling the old one attached to the new one? Is this a HUGE job or an easy one?

OK. I am curious how you know the power injection is working correctly. How did you test for that?

I would tune in an AM station. Then grasp the base of the antenna and wiggle it. If you get intermittent improvement, it may be that tightening the mounting nut under the headliner might cure the problem.

I don't know how to get under the headliner to the mounting nut on your car tho.

I guess I improperly used some words. I am assuming that the since the part number which has 2000 Jetta on the retail packaging would be properly installed by taking out the old radio and putting in the new one without having extra cabling with nowhere to plug. I do not and have not tested that the actual power is being injected into the system nor would I know how to accomplish something like. I would expect that I don't have the tools/equipment to do that.

It is as tight as I want to go. I didn't torque wrench it but it certainly is far from loose.

I can pull it down far enough to get a wrench on it and not ruining the headliner. I think replacing the cable is another story though.

I am not sure what you are saying in the above sentence. Repeated readings only suggest additional interpretations about your assumptions.

a. you assume that such a radio would have a built-in DC power injector such as the factory radios do?

b. You assume that the radio would have come packed with such an injector and that the installer would have used it and powered it by plugging into an available connector and not having to splice a wire?

c. something else?

So let's review what happened here. You took out a (working/non-working) factory radio and had it replaced by an installer (at/recommended-by) Circuit City. After the install, you tested the FM, and it worked. About _____ time later you noticed the AM did not work. You then (did/did-not) take it back to the installer and say it does not work, and that they should fix it.

I would expect that if you don't have a multimeter, you have a friend who would lend you one. What that thing does is pretty simple. Radio waves are high frequency alternating current. A capacitor can pass AC and not pass DC. An inductor can be looked at as passing DC but not AC. A resistor passes both, but it could be used instead of an inductor because it would only pass a little radio signal. So the injector circuit passes some DC to the center of the coax, which is used to power an amplifier at the other end. The presence or absence of such a voltage on the center conductor of the coax could be detected. It could be used to detect such thing as an injector being omitted, or the injector not being properly powered so that it could pass DC to the coax.

I don't know if you could access the center conductor of the coax at the base of the antenna. I don't know if that coax is removable or not. I was not looking for that when I got a wrench in there to tighten my nut. When I solved/worked-around my problem, I stopped looking.

I have also not checked what voltage should actually be on the easy-to-access thread to the whip. I would guess that the DC would not be present ( would be zero volts) up top, even in a good system. I am not motivated to go read it at the moment.

I was not thinking about mechanically tight. I was thinking about breaking thru any corrosion that might be impeding current flow.

And when I said to grasp the base of the antenna to wiggle while listening to an AM station you would expect to be able to hear well, I was suggesting the part of the base that is up top. Perhaps you understood that.

I took out a non-working factory radio (FM fine, no AM) and had it replaced by an installer at Circuit City. After the install, I tested the AM and FM, and it worked. About a few days later I noticed the AM did not work as well. Subsequent tests show that the radio works on AM sometimes, and FM all the time. You then did take it back to the installer and say it does not work, and they offered to seel me an AM booster. Since I do have MP3 capability now, and AM more then when I had the factory deal installed, I decided to take my case to usenet to see what I could do now, including, but not limited to buying a third radio for the car and do the installation myself the correct way.

I am not sure what I am supposed to test. Am I testing the antenna lead, the DC wiring, the speaker leads, what?

Antenna was replaced before radio was purchased as an effort to alleviate the AM problem. No corrosion in the new mast/assembly and the antenna is properly grounded to the roof.

yep