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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old May 8th, 2020, 10:36   #16
jhax
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After looking at the following thread (http://forums.tdiclub.com/showthread...72#post5588472) I suspect a grounding issue. Key turned to acc position and volume up I hear loud static coming from speakers until the glow plug light turns off. After that happens I hear light buzz, car on loud static returns. Pitch also changes with rpm. Voltage at alternator is 14.6v. Resistance from the ground wire plugged into the back of the radio to the opposite end of the same wire, not plugged in is 0.2ohm, resistance on the same end of the wire but plugged in to the chassis block under the dash is 2.4ohm.

Last edited by jhax; May 8th, 2020 at 11:04.
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Old May 18th, 2020, 10:22   #17
jhax
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Any ideas?
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Old May 18th, 2020, 11:28   #18
Almost1
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What input do you hear this on? AUX? Is the audio source also pulling power from the cigarette lighter? If yes, you have a ground loop. That only explains the noises you hear, but not the audio cutting in and out
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Old May 19th, 2020, 10:48   #19
jhax
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Yes aux, I assume we want 14v at the lighter?
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Old May 20th, 2020, 04:34   #20
Almost1
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Yes, the voltage is fine, but the problem is the ground for the radio and the ground for the lighter are the same, and un-isolated, and it gives a path for feedback. They sell in line isolators for the 3.5mm jack, or you could install an isolator on the ground of the lighter.

https://www.amazon.com/Mpow-Ground-I.../dp/B019393MV2
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Old May 20th, 2020, 12:48   #21
jhax
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Well I do get 14.4v coming from the lighter. However I do have a USB charger charging my zune all the time due to the battery on the zine being dead. I have had the same issue while just playing radio. But the zune charger has always been plugged in.
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Old May 21st, 2020, 05:03   #22
Almost1
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Then it points to a bad connection somewhere. Don't limit your search to just the radio ground, but the chassis and engine connections as well. The alternator creates a ton of noise, and if the connections are iffy it makes the noise more pronounced.

Check:
Battery terminals
Chassis ground by battery
Power connection on starter
Engine ground on trans bolt
Alternator mount
Alternator positive terminal
Fuse for the radio (both on the fusebox and the radio itself. Cheap fuses haze over on the blades and cause all kinds of issues)

The radio circuit grounds at the terminal strip above the fusebox I believe, so make sure that is tight against the chassis.
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Old May 21st, 2020, 13:50   #23
jhax
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Thanks sir. I assume I'm checking for 14v with car th bung at all of these points or am I checking ohms?
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Old May 22nd, 2020, 07:18   #24
Almost1
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Checking voltage and continuity is a good start, but the key is the surface area of the mating surfaces (also tightness as a loose connection means less contact area as well). The smaller the contact area, the less space the electricity has to flow and increases the signal to noise ratio of the system as a whole. It may test good with a meter, but removal and thorough cleaning of the surfaces would be the only way to make sure you're getting the best contact you can. I also read that the resistance of the ground wire from to the radio increased as you plugged it in. This is kind of hinting at what I'm talking about depending on where you measured when it was plugged in. Is it one that plugs right into the terminal strip above the fusebox? It may be worth squeezing the female connector to get a tighter grip on the terminal. A contact conditioner may be helpful, too. I like Deoxit Gold.
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Old May 22nd, 2020, 10:40   #25
jhax
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Sounds good. When I checked resistance for the radio initially I shoved one probe into the radio ground pin of the radio with the plugged into the radio and radio on. Other pin was shoved ok!raise to the ground plug into the grounding lug next to the fuse block.
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Old May 23rd, 2020, 08:30   #26
ToddA1
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Have you divorced the original ground and wired in a new one? That’s probably the least labor and easiest route, even if it’s only a test.

You did an engine swap.... I’m sure you have spare wire/terminals. I’m drowning in the stuff....

-Todd
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Old May 24th, 2020, 13:44   #27
jhax
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I have not Todd. You're just saying run a new ground wire from the back of the radio to the ground lug next to the fuse box and leave the old one hanging out so the lighter still has a ground correct?
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Old May 24th, 2020, 18:56   #28
ToddA1
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Pretty much, yes. Personally, I’d depin the ground from the radio plug, then insert a repair wire. If you go back to that multi-spade junction, be sure those terminals/ground point are clean.

You may want to go to clean metal to be sure you have a good connection, or find a firewall grommet, and go to the battery.

-Todd
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