Alternator Question

[Northboundtrain]

I recently installed a volt meter, and it's a good thing because the alternator doesn't kick on and start charging until I get the revs way up.  I have to rev the engine quite a bit higher than I do for normal driving (don't know how high exactly since I don't have a tach).  It seems like it's getting worse, i.e., I have to get the revs up higher than I used to.  Is this a common symptom?  Does it mean the alternator is getting ready to crap out?  Is it an easy fix or should I just replace the alternator?

Thanks

[fspGTD]

It is how bosch alternators are designed.  I switched to a lightweight denso alternator on my GTD, and it has a self-exciting feature... so don't need to revv the motor after starting to get the alternator to engage.  The problem with this design is if you sit there in the "ignition on" position for a long time, the denso alternator will drain a bit of current, and over itme it can drain the battery.  Quickly learned I had to no longer leave the keys in the ignition on when I wasn't using the car!

I just tightened the alternator belt on dad's '84 Rabbit Diesel "L" naturally aspirated.  It had a new belt and went about 300 or so miles on already and so it has got loose after getting "worn in".  I noticed that after I tightened the belt, the alt light went out much quicker than before.  So if you have the revv the motor pretty high before the alt light goes out, it could be a sign of belt slippage.

[Northboundtrain]

Thanks, It is a relatively new belt, so I'll try tightening it first off.

[Northboundtrain]

Well, now the alternator isn't charging at all no matter how high I rev the engine.  I pulled it and got it tested, and it tested fine.  14.5 volts was the reading on the testing machine, but it won't do this in the vehicle.  I've checked and cleaned all connections and grounds, so now I have to assume that I have a problem with the wiring itself.  

So can anyone please help me re-wire the alternator?  I have the wiring diagram and I sort of know how to read it, but since I have a volt meter I don't care about the warning light on the dash, so I'm not interested in duplicating the existing wiring.  I just need to wire it up in the engine compartment so that it will charge the battery.  The plug with three wires going into it that connects to the alternator is badly worn -- the wires are all frayed at the plug -- so I'd just like to replace it with spade connectors on individual wires.  

So is there a quick and dirty way to wire it up?

Thanks

[Rat407]

It is possible that the wiring is coroded under the caseing and you can't see it but it all looks good. I had this happen on my Impala, cleaned it all up and no start but click click click, got a new starter and same thing, come to find out the wire inside the insulation was really messed up, didn't see it till I cut it open.  Just a thought.

[QuickTD]

Does the alternator/battery light come on in the dash when you turn on the key? If not, this could be your problem. The current that passes through the light is needed to excite the alternator. If the bulb is burned out, it may take a good rev to get it going or it may not work at all.

[Northboundtrain]

No the bulb does not come on, and it never has since I've owned the vehicle.  Is this why I had to rev the engine so high to get the alternator to charge?  Can I bypass the bulb and just wire it up in the engine compartment?  I need help here, the manual doesn't give me a good enough understanding of the wiring to be able to gerry-rig it myself.

Thanks

[jtanguay]

don't know if this is much help, but once in the winter I let my gas golf warm up (forgot to rev up engine so battery light went out) and the battery + car died.  pissed me off lol...    

with my 86 jetta TD the alternator belt was pretty loose.. I had to tighten it every once in a while.   Highway driving charged the battery just fine, but after two or so weeks of city driving the battery would die (this while the belt was loose)

[veeman]

One place you might check is where the alt harness joins the main harness just below the bottom radiator hose.  For some reason, it seems like the alternator wires get stressed and cracked at that area.   I've seen this on two A1's that I've owned.  

The first car was my 83 GTI and it had the symptoms you describe.  Alt tested fine, but no juice at the gauge or in the car except battery volts.   I had to remove the harness wrapping material and splice in a new section of wire where it had broken  (10 ga, I believe).

[BlackTieTD]

No the bulb does not come on, and it never has since I've owned the vehicle.  Is this why I had to rev the engine so high to get the alternator to charge?  Can I bypass the bulb and just wire it up in the engine compartment?  I need help here, the manual doesn't give me a good enough understanding of the wiring to be able to gerry-rig it myself.

Thanks

fix that light first. stupid design... that light breaks the circuit if its not working.

...once you have the alternator working again, get a hold of a transpo adjustable voltage regulator. i got one for about $25cdn a few years ago. it self-excites the alternator. no more blipping the throttle... and you can adjust the voltage.

[Northboundtrain]

Thanks for the replies and help so far.  Some good advice and I really appreciate it.  I don't want to be a PITA, so I'll ask once more and then quit bugging you guys.  

Is it possible to re-wire the alternator to the battery such that the dash light is bypassed?  If so, can you give me a brief description?  

Maybe I'm asking a stupid question here, I don't know.  Any help/ideas greatly appreciated.

[QuickTD]

It is possible to rewire the alternator but you will have to have the light (or some other resistance of 50-100ohms) under the hood to feed the stator terminal of the alternator. If you bypass the light and hook switched battery voltage to the stator terminal it will backfeed the ignition circuit and you won't be able to shut the car off... I don't have an older bosch alternator kicking around to positively identify the terminals, so I can't really can't give you explicit instructions on how to rewire it. I would suggest just replacing the bulb first and see if that works.

[Hammy]

Black Tie;

 Where did you purchace the adjustable voltage reg.? That's a great idea.
 

[Northboundtrain]

So I seem to have gotten it fixed.  I replaced the alternator warning bulb and, for a backup (in case the bulb burns out again), I ran a wire from the fuel on/off terminal on the IP (a 12v source in the engine compartment that would be on/off when the ingition is on/off), through a 50 ohm resistor and spliced it into the blue wire that runs from the bulb to the alternator.  

Now it charges fine with no revving, and it doesn't seem to backfeed the ignition (the engine shuts off).  

Anyone see a problem with this set up?

Thanks for the help, you guys are indespensible.  :wink:

[QuickTD]

I see no problem with that setup. The bulb just limits the amount of current that can backfeed into the ignition circuit from the alternator, 50 ohms should prevent any "run-on" type situation.