Stupid Alternator Light....anyone have resistor diagram for instrument cluster?

FletchMan

Veteran Member
Joined
Apr 1, 2006
Location
Black Hills
TDI
2006 Jetta, 99.5 Jetta...previously owned 2000 Beetle and 1990 Jetta 1.6
So, I've been through all the paces for the alternator light. The alternator charges just fine once it kicks on (must be certain RPM) as there is a problem with the exciter wire / dash light combo. The blue exciter wire is 12v when I turn the key as long as I don't have it hooked up to the alternator. As soon as I connect it to the alternator, no measured voltage - just goes to 0v. So, everything would make me think it's the regulator. I replaced that - still the same result. Now I'm thinking there is a problem with the dash light and possibly the resistor. This thing should be going off as I know the battery voltage and alternator are equal and complete the circuit quite often. I then took apart the entire dash and removed the cluster. I couldn't tell what resistor should be measuring what and none look totally blown up. Anyone know what belongs to the alt light?
 

coalminer16

Top Post Dawg
Joined
Dec 11, 2008
Location
Central Wisconsin
TDI
Golf 2004
Just have to trace the circuit board to the red light. I think it is more of a diod though. With juice coming from the battery to the alt it goes through the key and the dash and excites the alt and also lights the red light up. Once the alt is excited and juice starts flowing out instead of in the light goes out as the volts coming out of the alt is higher then what the battery has so the current reverses. I also want to say there is a 3 prong deal on the circuit board on the dash that is common to burn out. I just can't remember if it works with the alt or not.
 

FletchMan

Veteran Member
Joined
Apr 1, 2006
Location
Black Hills
TDI
2006 Jetta, 99.5 Jetta...previously owned 2000 Beetle and 1990 Jetta 1.6
It turned out NOT to be the light at all. I just had 2 bad regulators and I'm pretty sure it's because I fried the second one - if not both. I did a lot of needless repair and removal but I guess it works now.

Funny thing is that when the car is idling without the lights or heater on, the light flickers. Not sure that means. It's not a big worry though.
 

coalminer16

Top Post Dawg
Joined
Dec 11, 2008
Location
Central Wisconsin
TDI
Golf 2004
Most do flicker a little. I think one of the poor man repair manuals it states to put a red nail polish on that light so it will mask that low idle glow. The alt needs a certain speed to produce and a diesel idles very slow anyways.
 
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