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Common Sense + Critical Thinking
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It would help to put your van's year/model/awd/conversion/etc in your profile or signature so we know what we are working with, not just for this issue, but for the future as well :)

To disconnect the alternator you don't have to remove the heavy gauge wire, just pop the other connector out and see if your problem improves. There is also a ground wire that is supposed to be attached to the engine cover, make sure that is in place.
 

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Discussion Starter · #22 ·
It would help to put your van's year/model/awd/conversion/etc in your profile or signature so we know what we are working with, not just for this issue, but for the future as well :)

To disconnect the alternator you don't have to remove the heavy gauge wire, just pop the other connector out and see if your problem improves. There is also a ground wire that is supposed to be attached to the engine cover, make sure that is in place.
Sorry, probably should have led with that info. For reference, its a 2000 base model passenger / cargo mix (three rows of seats + windows but barn doors in the back + manual seats, manual windows, fixed steering column, etc) Isn’t any sort of conversion vehicle, just something that was ordered by a local government fleet agency and wired up for a whole lot of equipment that isn’t here anymore. I’ll add that to my profile
 

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2003 Safari AWD
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Also... antennas don't have a ground. If they did, they would just be a wire sticking up in the air and the whole car would be an antenna.

So a rotten antenna mount could be a problem.
 

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1998 LS AWD Forest Green metallic
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NoQuarter wrote:
"Also... antennas don't have a ground. If they did, they would just be a wire sticking up in the air and the whole car would be an antenna."

UH, That poorly worded statement.
I am not trying to nit-pic here, and I think I know what you are trying to say, but any ham radio operator with much experience, would likely have a tough time with that statement, as written.
I would like to try to clarify that a bit.

All antennas work relative to some sort of a ground reference. Some are difficult to see or even visualize, and some are electrical 'equivalents' but they are still considered ground 'references'.
On a car, the antenna is insulated from the body ( with the car body being the 'ground' reference). From that insulated antenna base point, the lead to the radio is an insulated wire. It is inside, and insulated from, a shielding braid. The shielding braid is always supposed to be grounded to the car body at the antenna base ( and separate from the actual antenna mast).
One purpose of the grounded shielding braid is to drain off any static or interference that may be picked up along the way to the radio, such as tire static, or alternator or ignition noise.
A missing or poor connection from the shield braid, to the vehicle body, can allow more static and engine related noise ( alternator, fuel pump heater fan, ignition coil and/or bad plug wires wires, etc) into the signal you are trying to listen to.
Also, the poor or missing ground connection does not generate any noise of it's own, although there are specific rare cases where it can facilitate additional noises being generator. Those cases are very rare, and are usually associated with close by high powered transmitting equipment within the car.
Many ham radio operators have 'heard' ignition noises on their radios, and then seen the offending vehicle pass by ( old jeeps and old pickup trucks are common offenders )
Thanks for the bandwidth, and I hope it helped with a better understanding of the concept
Rod J
issaquah, WA
 

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Discussion Starter · #31 ·
So I’ve tried out a few of the suggestions I got on my last post. Thanks to everybody who left a comment, I learned a few things, and I’ve narrowed it down. First, the issue isn’t due to interference from the engines electrical system. I got the van up to about 40 mph, put it in neutral, and killed the engine. With the car coasting on nothing but it’s own momentum, the radio still kept cutting out. So I don’t think that’s the issue. I also eliminated the possibility of a grounding issue (see the attached pictures) and it made absolutely no difference. That’s not the problem either.
Electricity Gas Engineering Computer hardware Electronic engineering

Hood Automotive tire Motor vehicle Electrical wiring Automotive exterior

Rectangle Font Parallel Slope Number

So, the only other possibility at this point is the antenna itself. I’ve heard a few things on my previous post, but I’d really appreciate a fully detailed explanation or schematic of the full antenna system. I don’t think this is the issue (everything seems fine after a minor inspection) but this is the only other thing left that I can think of. The Bluetooth capabilities on the new head unit work and sound perfect at any speed, so I know for sure this isn’t a grounding issue.

Once again, I really do appreciate all the help I’ve been getting with this issue the last few days. It’s nice to be on a vehicle forum where people don’t treat you like an idiot.
 

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01 Astro RWD Cargo, 97 AWD Mark III
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Even a weak am station can be pulled in from a good distance.
Does your head unit use an antenna adapter?
These are easily damaged when removing. The braided shielding pulls loose degrading the antenna ground. You can easily check by removing the adapter and just use the factory antenna cable.
 

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Discussion Starter · #33 ·
Even a weak am station can be pulled in from a good distance.
Does your head unit use an antenna adapter?
These are easily damaged when removing. The braided shielding pulls loose degrading the antenna ground. You can easily check by removing the adapter and just use the factory antenna cable.
There’s no adapter required, it’s a stock head unit that has a Bluetooth retrofitted into it.The antenna cable is just the regular plug style
 

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01 Astro RWD Cargo, 97 AWD Mark III
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I see 2 issues
1. I have never seen an antenna coax in an Astro that is long enough to reach the left side like that. There has ro be an adapter on it to make it longer. There is not much for a wiring schematic for the antenna. It is just the coax out to the antenna mast.

2. What is that yellow wire scotch locked to both red and black? Or is it just red and black only?
Red and Black are typically power and ground. That would be an instant short. Is that your ground test lead?

It looks like the factory connector was removed and the harness modified.
 

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2003 Safari AWD
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I don't recall what you said about which stations are cutting out? You have verified it is all stations and just testing the same one ? How long do they cut in/out?

Not much to learn on that schematic about the antenna. Center wire in the coax cable goes to the antenna mast.

The antenna mount needs to be in good condition so that it can't be contacting the body such as corrosion under the mount.

The coax has the shielding wires which are connected to ground so the cable has to be in good condition so the center wire can't contact the shielding wires.
 

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2000 Lifted 4x4 Astro 92 V8-350 Shorty
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As I stated LONG ago.. if you don't get good AM reception, then there is likely an issue with the connector or cable to the antenna. There could also be an intermittent break at antenna mount, which also seems likely if you have issues once moving.

It's a simple thing... connector > coax cable > antenna

FM signal will travel across a broken connection, but AM won't. You should simply test for connection (with ohm meter) between tip of connector, to antenna itself. If your antenna is coated, then unscrew antenna rod from mount, and test at antenna threaded mount. You also want to be sure the is no short between center pin of both mount or connector to outside connector (shield).

The antenna base should have a firm connection to fender, with no short between ground and center mount. But again, needs full connectivity between antenna rod itself and center-pin of connector.

This is a very simple thing.

Also, you never supplied a photo of your connector as asked. Typically GM uses a "mini" connector, and aftermarket uses a "standard" mount. An adapter of some sort would be required if using an aftermarket radio. Sometimes these adapters can be loose or intermittent.

Here's an example showing mini GM connector to standard antenna adapter.
Font Electronic device Auto part Wire Cable


Yours would likely be standard to mini (like photo below) if using aftermarket radio
Office supplies Writing instrument accessory Stationery Writing implement Metal
 
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