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General Information => Troubleshooting => Topic started by: burn_your_money on November 10, 2006, 06:04:28 pm
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I just got my car safetied so it is still new to me. It's a 92 1.6 TD with a tach. My alternator does not work at all below 4k. Once I rev it past 4K my tach will bounce up (from 0) and the battery light will go out. I replaced the brushes in it so that isn't the problem. Could it be a poor connection? I tried swapping the alternator with one of my spares but the mounting points were differant
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Could be a bad connection. Might also be a loose belt....check the tension on that too.
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Oh the belt is quite loose, I can spin it 360 degrees. I hate mk2s, my mk1 was so much easier to work on. It doesn't squeel though.
Also, prior to me removing the alt the belt was tight and it still didn't work
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Thought about it a little more...if it works over 4K but not under, I would say it's an internal problem. Does the alternator put out any juice? Or is it just that the tach isn't woking and the light is on?
It might be whatever they use to pick up the signal for the tach/light inside that is faulty. Or if the alternator isn't putting out any juice, it's time for a rebuild. Any decent alternator/starter shop can test it for you, as will Canadian Tire and I believe NAPA. Most places don't charge much for this and it might save you some headaches.
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The alternator is putting out nothing. No power, no tach signal.
I remeber when I bought the car the guy said that the alternator had to "warm up" before there would be a tach reading. He reved the engine a bit and then the tach started working...
If I could afford to have this alternator rebuilt I defintly would, however I'm strapped for cash so I'd like to either fix it myself or make one of my other alternators work, whichever is easiest
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I can relate to the strapped for cash scenario.
I don't usually get into rebuilding mine....a friend of mine does it (very reasonable I might add) so I just take them to him.
I'm trying to remember when I had mine rebuilt off my MK2 what else he replaced besides the brushes, but I'm drawing a blank as it's been a few years.
Just a wag, but it might be the windings....not sure.
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Seeing as you have checked the obvious things like a loose belt then your alternator more than likely has a failed diode on the rectification side of the output. A 3 phase alternator in an automotive application usually has a 6 diode full wave rectifier which renders the AC into DC current. Loss of one diode on the bridge will result in low output at moderate speed and no output at low speed. The rectifier/regulator on the VW is replaceable as a module for a modest price. Then again maybe it is the brushes? or maybe a poor connection internally...
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Thanks for jogging my memory Doug..it was the rectifier he replaced on mine (along with the brushes).
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I already replaced the brushes. Do you have a picture of this part? I have spare alternators that will gladly donate thier internals to the cause
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I tried to google it but only found one for a Bosch alt on a Porsche.
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I'll have a look in my mk1 bentley
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That should give you an idea what it looks like.
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Seems to me it bolts on the back side of the alternator (Bosch) having a few cooling fins on it and is shaped like an old style hearing aid as in slightly eliptical?? I am sure if you go to the book they will show you a picture. Last time I priced one it was about 30 bucks or so. My idea on the subject is that when the regulator/rectifier goes the rest of the alternator is not far behind unless it is not old. If it is old, then spring for the rebuilt as you get the new reg, brushes and bearings plus a five year guarantee at CTC.
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This link is the best I could find showing a regulator and rectifier. Not sur eif they are exactly like yours or not. I'm on dial up, so searching is not easy.
http://www.wagneralt.com/catalog/flyer/Monthly%20Ad%20NOV%202005%20web.pdf
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i agree with the diode pack theory, but usually if a diode goes down this is seen by the charge light staying lit but very dim. you can also change the hand of an alternator. you mentioned you had another one spare?
is it the same type with the W terminal?
would it fit if you changed the alternator hand?
in other words remove the allen screws that hold the two body halfs together, and rotate 1 half until the hand is swapped then replace screws, i've done the same thing for my bus, i have 90amp passat alt, instead of the 55amp standard jobbie.
or failing that replacement of the diode and retif pack which is a soldering job but not really hard.
hillshy
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My two alternators are identical, the one works perfectly but has the wrong mounting points.
I'm definitly not understanding this rotating bit, hopefully it is in my bentley when I find it.
Actually now that you mention it, at idle and when I rev the engine below 4K, the battery indicater light does dim
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burn_your_money,
check this link:
http://images.google.co.uk/images?q=tbn:rq0s9fCQwhGz2M:http://www.electricboatparts.com.au/persistent/catalogue_images/categories/100001
The atlernator in the picture should be more of less he same as your's with 3 mounting points(bosch), 2 on the front half (pulley end) 1 on the other/rear/diode end). see the 4 brass coloured screws in the chassis, if you were to remove these then you could if needed, rotate the rear mount 180 deg clockwise to change the mounting config, depending which side of the engine the alternator sits.
You have an alternator that has different mountings,
is this how it differs? what was it off?
ps the pulley also has to come for the mod?
hillshy
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is your alt like this:
http://www.iat-usa.com/fpdb/Images/al1057b.jpg
then the hand thing wont apply, I think our vw engines came with at least 2 different types.
Hillshy
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I have this style alternator
(http://www.iat-usa.com/fpdb/Images/al1057b.jpg)
The differance between the 2 is where the 2 mounting holes are (the ones that share the same tab) One hole is threaded, one isn't. The threaded holes are opposite on the trannys so the rear mount doesn't reach. I know I could just use a normal bolt and nut but I don't think the belt will stay tight.
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The 4 screws that hold the 2 pieces together are stripped to hell, what's my best option? Getting a reman? Drill them out and then hope I can use vise grips to remove them?
I got my spare apart easy enough
Thank you all for the help so far, it's very much appreciated
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Hi burn_your_money,
you say that you could if needed secure it with a normal bolt but the belt might not stay tight, if you managed to mount it with a normal bolt i'm not saying you should but if you did and you wired it up, if it works then a least you would know 2 things for sure.
1st) the new alt works fine, as all problems have been cured.
2nd) the old one was faulty for sure, as per the problems stated.
you would then be able revert back to standard mounting Alt as nothing has been changed, then using parts from to new Alt to fix the old Alt were not in vein, that's probably the way i'd go.
decesions decesions eh :?
good luck tho!
Stu
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I actually tried that last night but one of my spares, the mounting point at the top where the bolt slides through is too small to accept the bolt. I don't want to use a smaller bolt incase of damaging the threads on the mount.
I then tried my other spare but the lower tab with the 2 holes in it is closer to the alternator body so the lower bracket does not fit in. It was an extremely frustrating night.
I do have 3 other alternators though, one is siezed, the other is almost siezed and the other is on my rabbit which is parked for the winter. The rabbit one works but has a differant style connector. The 2 siezed ones are the same style as what I need too :(
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Hey mate,
i guess you don't have any other options but to rebuild the present one, fustrating i know, but to look on the bright you seen to have nuff parts/spares to make one good'en without havin to pay out shed loads of cash.
i've also had a $hitty week, tuesday eve, a bus ran my wifeee into another car so she so ended being sandwiched between it and another car, the whole front end of our car(subaru turbo wagen) both front wings, 2 front doors and both front alloys were bashed to Łuck, currently undrivable, thankfully she and my 3 yrs old son were ok apart from shock but ok otherwise.
thursday, while sitting down for dinner, heard a gushing sound followed by drip drip drip splash drip drip,i look up and see water leaking from the ceiling above, an upstairs water pipe had burst!!! could have waited until after dinner. ended up joing to hell n back to sort that mess out.
what a week :lol: , gota shugg it off and lol about it...
Hillshy.
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Wow man, your week sounds way worse then mine. I'm very glad to hear that your wife and son are alright :) Pity about the car though. Was the upstairs waterpipe one of yours or a tenants (aparetment building style)?
I ended up buying a rebuilt alternater. It set me back $180 but it comes with a 3 year warranty. I tried to rebuild mine but the screws were so rusted in there that they stripped so I just gave up and got a rebuilt.
The only thing now is my tach won't start working until the engine hits 2500 rpm. I could drive all day and not have a tach but as soon as the RPMs exceed 2500 it works perfectly. My driving style has me shifting around 2250 so sometimes I don't get a tach for quite a while
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sometimes i gotta blip my throttle to get my tack sensor to work too. if the engine has ran in the past while sometimes the tach kicks on after a few seconds of being started... if you blip the throttle above 2500 does it kick the tach on? is that the case or no? if not then what a weird problem... better connect a multimeter up to the tach wire and see whats up... maybe the rebuilt one is messed?
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Yes if I blip the throttle above 2k the tach kicks in right away. I just find it weird because my other jetta tach would actually work while cranking, so I knew the cranking RPM.
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evening all.
Burn y money, lucky the pipe was inside my house, My bro had fitted shelfs into my sons room and hit a water pipe he caused the leak, but to be fair you would never have guessed there was a 15mm pipe hidind behind a fitted wardrobe, all sorted one and i'm start'n to see the funny side to it, still really pissed about the car tho :( , glad to hear the alt is sorted.
jtanguay- your prob seems similar to mine, but then i did the rev mod, that is mentioned on this site, it seems the alt needs about 20 sec's to start after the engine has been run, then it jumps into life and is fine from there onwards.