Gas alternator onna 1.6 diesel?

[trev]

The junkyard butchery continues!

 Bearings blew up on the alt that was in the car. Only alt I had on hand was a near new one taken off a gas VW.

 Now I'm not charging.

 Did the test on the Battery light, grounded it, and the light comes on when the key is on. Does not come on when the wire is connected to the alt and key on, and not getting much in the way of voltage, if any at all.

 Wondering if the field windings terminal (on the gasser alt) needs to be wired in to excite the windings, and if so, where to tap in the wiring.

One possibility is to jumper straight from the D+ connector. The other is to split off from the fuel shut off solenoid wiring (so it shuts off the voltage when the key is off)

 Anyone got any info worth sharing?

I can follow a circuit diagram as well as most, and am not too scared of doing butchery inside the alternator if I gotta, having built a few from parts, but this alt is a near new rebuilt, that was going to be a parts donor for a build, but got called into service before it could get stripped. I even bukshee'd up a tang to allow the stock diesel tensioner to work. But the lack of charge, is annoying.

Cheers
  Trev

[Rabbit on Roids]

gotta have the right alt for your charging system.. i tried using a 92 Jetta alt in my 85 GTI, and it DID NOT WORK.. same symptoms too. i would say it needs to be the right alternator possibly..

[OM617]

gotta have the right alt for your charging system.

An alternator doesn't care what engine or battery is used. All it cares about is it has a good ground, a path to send current and a field coil power source.
I use an alternator from a Saab 900 on my cars, why does mine work but his wont?

[trev]

Well, to add some details from today's execise...

Found this step by step guide to troubleshooting the alt off a Audi. http://www.audiurquattro.de/ralf/infos/pdf/Alternator.pdf It has a pretty detailed troubleshooting run-down, so, off I went to the races with my multimeter.

Everything I was able to check, came up looking OK. I stripped the alt to pieces , desoldered the stator wires, and all looked good. Reassembled, I started looking over the stuff I had read here about voltage drop, and began checking that.


Found out that the 1 gauge copper lead off my positive terminal, had some issues. Well, one actually. Despite looking good and feeling solid from a cursory check, the lug on the starter end of the cable was best described with words that the forum software will censor out. <sigh> Corroded and rotten are barely adequate. Off to Ctire to see what they have in stock. Ended up buying a self crimping connector that said it was for a 1 gauge cable, but turned out to be too small. So I grabbed a torch, some rosin core solder, and went to town on it and soldered the remains of the new lug, onto the cable.  Better.

Charging now, at least after revving it up a bit. Showing 13.7v-13.8v on the digital voltmeter I hacked together from some Princess Auto bargain bin stereo parts, plugged into the cigarette lighter port. Found that the reading would go up by .1 volt if I jumpered the output direct to the pos terminal with my crappy jumper cables.

As it stands, tomorrows project is a new lead from the Alt to the Starter terminal, as I am seeing a bit of drop across there. If I measure the voltage at the battery, I see 13.8v. If I measure from the output terminal straight to the battery, I see 13.9v, so I think there is a gain to be got there.

Still no darned battery light. Lights when the Blue lead is shorted to ground, still nothing when it is connected into the system.

Oh. With regards to the 'field' connector, it is supposedly connected to the same plate as the D+ lead. I tried the manual excite route (Jumper cable, connected to the Pos terminal, touched the field lug on the alt) and the engine immediately grunted and bore down on the load, an the voltage jumped up to near what I was hoping to see, from the steady 12.7 or so that it was showing before this little operation.

Got no changes when I started jumpering in extra grounds anywhere i thought might be suspect, but am going to go around and see what they look like under the attachment points anyways.

We'll see what comes tomorrow.

Still trying to figure out why that light wont work. Dunno if there are changes from the Alt styles, or if there is something else going on with my car. The link I posted above, mentions some specific resistance values to look for. Mine were not near those, but the vehicle is not the same either, so I dunno if that matters so much. IIRC mine measured around 610 Ohms. I'll check that out again tomorrow as well as checking if it gets battery voltage or if it is dropped a lot (didn't think to check the voltage at the time, been that kind of day)

 
Cheers
  Trev

[Rabbit on Roids]

gotta have the right alt for your charging system.

An alternator doesn't care what engine or battery is used. All it cares about is it has a good ground, a path to send current and a field coil power source.
I use an alternator from a Saab 900 on my cars, why does mine work but his wont?

guess what? my GTI has a SAAB alt too. but its THE EXACT SAME as a VW unit that came off it. the 92vw alt wont charge on an 85 GTI.. plain and simple..

and the OP isnt using a SAAB alt, he is using a GAS VW alt..

[trev]

Awright.

Two days along, and other than keeping a close eye on the charge voltage (flat battery volts until the revs are blipped up, then I see 13.7-13.9v) I have not done much else under the hood.

I'd still love to know why no light from the battery/charge warning.

Kind of PO'd about the fact that I did not notice when it went away, too. No idea when that happened.

On the upside, I was rooting around in the shed and came up with two near new tires that will fit my car, that were taken off the wife's last car a short while before it got sold. Bonus!

I had a look at the wiring in my bud's gasser, and it looks pretty much the same as I have now. Dunno. Should work. Doesn't.

Cheers
  Trev

[dl_sledding]

Warning: IANAM (I Am Not A Mechanic), but here's a couple of ideas:

What are the differences between the pulley sizes of the gasser and diesel versions of the alt?  Is it possible that the alt is just not turning fast enough as compared to the gasser, which will typically run a higher RPM?  You did state that you are seeing a positive charge, though it looks like it's about a volt shy of what is considered normal.

I believe that any alternator should work *if wired properly*, as OM617 stated, as long as the voltage matches (a 12v alt on a 12v system, a 24v alt on a 24v system, etc).  However, it has to spin at the proper speed as well.  Hence, the pulley question.

What condition is the battery in?  Is it possible that the battery is bad enough not to allow a full 14.8 volt charge to be built up?

Again, IANAM, but a couple of somethings to think about from an objective view, anyway.

[Rabbit on Roids]

they still have to have the right voltage at the exciter (D+) wire.. and i would be willing to bet that its not right. i know that a GOOD 1992 jetta alt, would not charge on my 85 GTI. it is physically the exact same alternator. no light on the dash, no charge at the battery. i know it works, cause after that i hooked it up in a 90 jetta and it worked fine..

not all alternators are created equal. some have a one wire connection, and dont need an exciter wire. and those ones are WAY UNIVERSAL.. while ours are a little more picky.

[dl_sledding]

they still have to have the right voltage at the exciter (D+) wire.. and i would be willing to bet that its not right. i know that a GOOD 1992 jetta alt, would not charge on my 85 GTI. it is physically the exact same alternator. no light on the dash, no charge at the battery. i know it works, cause after that i hooked it up in a 90 jetta and it worked fine..

not all alternators are created equal. some have a one wire connection, and don't need an exciter wire. and those ones are WAY UNIVERSAL.. while ours are a little more picky.

Exactly!  One just needs to know all of the particulars on how the particular alternator works, and then wire properly.

However, it sounds like trev is having *a little* charge, which makes me think that the D+ wire probably has 12v on it or he wouldn't be getting any charge at all.  However, rotational speed could be a factor.  And, a bad (internally shorted) battery will cause the same conditions that he is describing; I ran into this on one of my kid's vehicles.  We thought the alternator was bad, and in the end we replaced the battery (which was still holding a low charge, but didn't have a lot of cranking life).  The battery was only a couple of months old, which pointed the finger elsewhere at first.

Like I said, IANAM, and it's really hard to troubleshoot without actually being there testing things, but hopefully trev has some things to try here...

[trev]

WRT the pulley question, it is the same pulley that has been on it for , well, since I first got the car. The ones that came on the rebuilt alternators, have not lined up, so the pulley has traveled from alt to alt. The pulley that is in use, is a machined cast iron or steel unit that was on the alt that was on the car when I got it. No idea why the 'stock' pulleys do not line up, but they don't. Diameter worked before, should work now. If anything, it's a wee bit smaller diameter than the stamped ones. Not running a tach, so no real need to worry about the exacts.

Had issues in the past, with a flickering charge light. Rev it up a bit, done, but that was IIRC two alt's ago. Bearings died on this one. When I was under the hood looking at it, found the excite (blue) wire hanging loose. You don't get the light without a ground path through the blue wire. No idea when I first lost that.

My alt charges quite well providing I blip the throttle to get the alt to excite and start charging. Saw 14.0v on the Voltmeter this week a couple times. Don't have an ammeter to check the output with though. Should track one down.

At this point I am wondering if I knocked out a circuit trace on the instrument cluster, or if one is starting to get corroded along the circuit for the excite circuit, to increase the resistance enough that it cannot get enough current through to fire up the alt, yet still allowing the light to light when the terminal lug is grounded out and the ignition is on.

Gonna require some more homework. Maybe this weekend. Gotta change the shocks out on the truck though. Ugh.

Soooooo....Back to pondering. I was hoping someone here had been though this before. So I might as well be the one leaving a trail of crumbs, as it were..

Cheers
  Trev

[Rabbit on Roids]

take the alternator back off, and clean the contact points everywhere it bolts to a bracket on the engine. and then clean the brackets where the alt mounts up to them. or did you already? because its amazing what a good ground connection at the alternator will do. that "early morning throttle blip" is no longer necessary after that most of the time.

[trev]

Well. Ruled out grounding issues.

Ran a new, number 4 wire from the alt straight back to the Neg terminal with zero beneficial effect. Scraped clean surfaces, soldered the lugs, cleaned them with scotchbrite, and bolted everything up nicely. Now satisfied that grounds are not the issue. At least not these ones.

Looking more like inner workings issues of the circuit from the positive through the instrument cluster, and onwards to the alt.

Troubleshooting for the next time I feel the need to rip my dash apart again, I guess.

Meanwhile, running OK, and charging once the alt is excited by a bit of revs.

Cheers
  Trev

[theman53]

I would be fine with the alt charging with just a little blip of the pedal.

Just curious as I just put a gasser alt on my diesel. What did you do to hook it up? My gasser had a push in plug with 3 spades and my diesel setup just has rings to go on studs. Just wondering what I should do about that.

[Rabbit on Roids]

build an adapter, that way you dont have to cut up your harness..

[theman53]

what MKII terminals go to the MKI posts, That is more what I was looking for as it is unclear. Yes I will build an adaptor once I know what is up.