2003 Jetta Electrical Gremlin Redux
All,
2003 Jetta ALH 190K. Pretty much same symptoms as described in this post. Bone stock vehicle. Symptoms start out as ABS light, beeping, radio light flickering, then progress to complete dash light, blower, radio, headlight cutout. Key on / off will potentially reset. Symptoms have never been present with key on, engine off. Correct battery, charging fine, new key switch, several new relays, batt grounds under box cleaned, no VAGCOM codes ever. Several posts have mentioned engine rpm. If I push the clutch in on the highway and let the revs drop to idle, symptoms occur, then back to normal. Can produce same result in driveway by revving to 2k and letting it fall back to idle. Cold / wet / rain has no bearing on this bug for me.
For the most part, this bug either occurs or doesn't: If the radio light is solid, non-flickering at startup, bug will *usually* not occur. Once a couple engine start / stop sequences happen, usually it's then fine.
So here's the slightly weird part: Pulling the battery hot cable off will chase this bug away for anywhere from 3 weeks to 3 months. Consistently. I believe most of the "this is now fixed" conclusions due to cleaning a ground, etc., are really just some sort of temporary "reset" due to having had the battery disconnected.
To summarize: This feels like either a voltage regulation issue (alternator) or a relay that is not always latching correctly. I would really like to know more about how this vehicle regulates and switches from alternator output to battery, but I'm not sure even a real schematic will help here.
My Valero 120A alt. has 70k on it, so that's up next, but others appear to have tried a new alt. with no success.
Thanks in advance for any new insights.
Aaron