A Thought on Altenator Exciting

[somolovitch3]

Instead of reving to 2000 RPM, one could run a wire from the Red/Blk 50 line (ingnition starter feed) via a 5 amp diode to the Blue D+ wire to the altenator. This will supply ~ 12 Volts to the Altenator wile cranking only, and should Excite the Altenator at a lower RPM.

I have checked the voltage of the D+ wire and it is only 4.8 volts once it leaves the LED-resiter combonation in the cluster.

Coments?

[the caveman]

Everytime i have checked at the blue wire for charging issues, there was 12v. When you saw that voltage was the car running? And/or was the light on or off .

[8v-of-fury]

I think the problem with it having to rev to 2 grand to excite the alt is because there is a significant voltage drop between the alternator and block (ie. a bad ground of the charging system..)

Burn_your_money had a simlar problem but I think he fixed it with a short ground strap from the alt case to the block somewhere.. Search for his voltage drop thread.

[somolovitch3]

The voltage was with the key in the on position, not running, light on. With the car running voltage was 13.8  I have a ground from the Alt frame to the upper starter mounting bolt and then one to the Batt negitve. In fact I hve more leads from Batt Neg and Batt Pos then VW thought of.

Pos from Batt to starter, from there lead to Alt out, lead from starter to secondary fuse/relay pannel ("pimped GP's", Head Lamps, other). Okay I am leaving out the leads via fusable links and others.

Neg from Batt to upper starter mouting bolt, from there to ground on trans mount, to the Alt frame (Strap from Alt frame to block, lead from Alt frame to head).

All leads from Batt are of weld wire #02. The smallest lead is #8.

It (Alt) will produce 13.8 volts at/above 1500 RPM, and once "excited" will continue to do so down to 300 RPM...okay then the engine tends to stall, or just dies.

[Vincent Waldon]

I think the problem with it having to rev to 2 grand to excite the alt is because there is a significant voltage drop between the alternator and block (ie. a bad ground of the charging system..)

Yuppers... that's the usual sign, particularly as our beloved MK1s and 2s start to get pretty long-in-the-tooth.

Just my opinion:  might make sense to fix the root cause of an alternator issue as opposed to figuring out a work-around...a properly running alt will excite immediately with the stock wiring.  

Case in point: I've owned my 1992 gasser since it rolled off the showroom floor... literally. Same alternator for the last 5 years... and just recently I noticed the old "blip the throttle to get 'er charging" issue creeping in.  Same dash, same battery, same alternator... but suddenly it needed a blip.  Redid all the big grounds... problem solved. Not saying its always as simple as a big ground problem, but that's the general idea.

[somolovitch3]

Okay what "Big Ground" am I missing? Really appreciate the help!

[8v-of-fury]

Engine -> Battery, Battery -> Body, Body -> Engine, Engine -> Battery

That's all I can think of really.

[Vincent Waldon]

Okay what "Big Ground" am I missing? Really appreciate the help!

Well, based on your post above you've definitely got the bases covered. 

A couple of thoughts:

- the cluster's ground could play into this as well... there's generally a big star ground on the drivers side by the fuse panel that bolts to the chassis tin... sometimes water gets in there and corrodes the connections or the mounting screw itself

- perhaps a voltage drop would be diagnostic... if you search here Tyler's done a nice write-up.... basically you load the system with a good sized load and then use a sensitive multimeter to check for voltage drops across all the various connections... in this case, positive and negative.

[somolovitch3]

Would this be the starfish looking one? Upper left hiding behind dash panel? And really fun to get to!

[burn_your_money]

Would this be the starfish looking one? Upper left hiding behind dash panel? And really fun to get to!

Yeah that's the one.

[somolovitch3]

May I state for the record.........Egg Suck!

[somolovitch3]

Update.......Kleened everything w/600 grit wet/dry/contact kleener and ...........no change. My friendy PITA Starfish was tight and clean, NO corrosion ( my I eek now?).  Ataching the 2 14 ga wires back to the Alt (replaced by the 4 ga to starter/batt connection when I upgraded to the 90 Amp Alt)(But left hanging) got me down to a "kick-in" RPM of about 1100.

Looked at the voltage drop DIY (I guess with that kind of smarts, he can burn all the monet he wants, although save some for new leads?). I am seeing 14.3 volts at the Alt B+ term and 14.2 at the Batt + term. Not chasing that .1 volt down.  Don't think it has to do with the "kick-in" RPM.  (Since my "helper" is a remote stater switch, throwing things at helper .......not recommended).

Any ideas as what next? Anyone seeing Batt voltage at the D+ term when car is switched on/not running? Makes me SO NOT want to get into the cluster/"printed " circuit ...........mess.................

[TDDrew]

You seem to have gone overkill with the grounds. Which is exactly what I was going to do for that same issue. I have an A1. I was reveiwing the wiring diagram and it seems that the alt indicator bulb gets power through a voltage stabilizer. Maybe that has something to do with it?

[TDDrew]

Did some looking around, maybe a worn alt indicator bulb with high resistance would cause this issue. Makes sense. I have never replaced the bulbs. Or the wrong bulb wattage is in there.

[somolovitch3]

Actually, Alt LED does not get power from stablizer (in Cluster). Comes up off of the 15 (Ign feed). Goes thu LED and down blue wire to the D+ (excite) term on ALT. When both sides see the same voltage, out goes LED. Although, looking at the diagram, the LED is installed backwards (in diagram) for it to light, wrong current path flow. It looks like they are all backwards. Current flow is from base of triangle toward point/bar. Hmmmmmmmmmmmm. If LED lights, it's good.