[MrMoMo]

Well... it seems I may have found the source of my power drain issues... When I first started looking I was using my amp clamp, and found that I had a 3A drain on the white wire (1984 BJ60). White wire goes to a multitude of things, including the alternator... So I clamped the wire at the alternator and got a reading of 0A. moved on to everything else to find nothing.

Came back to the alternator today (a bit warmer outside today at -14°C plus windchill). After pulling every interior fuse with no results, I clamped it again and found that there was acutally a drain through the alternator (I must have hit "hold" on my clamp last time I clamped it - the hold button is in a very bad spot!)

So... I disconnected the white wire on the alternator and guess what.. no more power drain from the batteries. SO. I guess this means that my alternator is the problem.... Wanting to understand it a bit more I took some more measurements, as indicated in the pictures below.

First picture: B post to Alternator case, the only scale on which I can get a reading is 20Meg Ohms - and I get a reading of 7ish Meg ohms. I am assuming that this is the insulation of the windings. Seems fine to me.

Second picture: Alternator B+ wire (disconnected) metered to ground (battery connected). No reading on any Ohm scale. (seems normal)

3rd & 4th pictures: Meter set to diode test, 2nd pic with leads reversed. Should I not be getting a reading of OL one way? Does this indicate a blown diode?

How hard is it to tear down/fix these alternators for a blown diode?

Thanks!

Bruce

[MrMoMo]

4th pic...

[dfmorse]

Good work. The diodes should be checked when removed from the alternator,because of coil loading, etc while installed. The BJ60 engine manual will cover disassembly of the alternator. Manual 98126, which covers 1974 FJ40 will probably do. An auto parts store may be able to get u the proper diode rectifier pack.

...

[lovetoski]

Originally Posted by MrMoMo

How hard is it to tear down/fix these alternators for a blown diode?

I'm not an alt expert, but as far as I know, this is a common reason why alt's fail. I think this prob is easy to fix - if you know how. I don't...but the alt repair shops I've talked to see it as "easy" to fix.

[MrMoMo]

Well, this might have something to do with it... I have continuity between the two brushes... and no continuity for one of the brushes to any of the screw tabs

Any thoughts?

[MrMoMo]

Now, with the brush holder removed I get some different readings...

Open line from B post to case, (diodes working)
585 Ohms with lines reversed (diodes flow this way)

[MrMoMo]

Rotor resistance seems fine now (it's cold) - it measured OL when measuring through the brushes - likely because of what I found with the brushes, one of them is OL somewhere.

Now.. How do I go about measuring the brush holder and the IC regulator?

Is it available as a seperate part? -And is that looking like my problem area?

Thanks!

[Pin_Head]

If there is a current drain on the large white wire that goes to the B lug, it pretty much has to be a bad diode. You can't tell which of the 6 is bad without disconnecting them so that you can test them individually, which is a PITA comparable to just replacing them. It is easy to test: Check the resistance from the B+ lug to the case and then reverse the leads and chack again. In one direction the resistance will be low and in the other it will be very high (several megohms). If a diode is bad, the resistance will be low in both directions. Just get a new alternator if the diodes are bad.

[MrMoMo]

Ok folks, I think I might have found it... If not, I'd be surprised...

Pulled the front end off, and found this wire shaved right down to copper. This would definately have been coming in contact with the rotor, and I can only guess it would have been grounding out through there.

Now, I have pushed the wire back in place and coated it with Epoxy to re-protect it.

Going to clean and further inspect the brush holder...

[MrMoMo]

Well Call me surprised.

THIS SUCKS.

Got it all back together - it meters fine, open line one way and low resistance the other way - but once installed the alternator is drawing 2.5Amps.

Where is the best place to get an alternator, and how much should I expect to pay (perhaps this should be in the diesel section now?) Is it possible just to purchase the Rectifier?

I just want to be able to drive the dang thing!

[haryv]

By chance were you running any excessive loads or perhaps jumping a car or truck when your vehicle was running? Excessive loading of the alternator can fry a diod and cause it to leak. Best to take the diods out and do a diod check on them and see if that is the issue.

BTW we cannot advise you where to buy a alternator unless you tell us where you live.

[MrMoMo]

Originally Posted by haryv

By chance were you running any excessive loads or perhaps jumping a car or truck when your vehicle was running?

Nope, I didn't do anything... just started all on it's own. (odd though, nobody around here believes me about damage from boosting with a running engine...)

Originally Posted by haryv

BTW we cannot advise you where to buy a alternator unless you tell us where you live.

Ahh... I was looking for a general place...i.e. Napa, or Toyota. I am near Kingston, Ontario, Canada - and it's a BJ, not an FJ.

[mobi-arc]

WAI Canada - Toronto Warehouse
34 Alex Avenue
Vaughan, Ontario, L4L 5X1
Local: 416-740-9200
Toll Free: 1-800-387-2807
Fax: 416-740-5348
Toll Free Fax: 1-888-502-1056

[MrMoMo]

I decided to rip it out again...tore it down and took the stator/rectifier to a local auto-electric shop - they told me they would have it ready for me tomorrow, called me a few hours later to say that the stator was fine and the diodes needed to be replaced. I should have it back tomorrow and re-installed again tomorrow night.

Quoted between $60-$70 CDN - we shall see...

[mobi-arc]

While they have it open, they should replace bearings and brushes as standard operating procedure when opening up the unit.

[MrMoMo]

It has been rebuilt recently, the bearings and brushes were fine, they replaced the diodes and checked the stator, it was fine.

Total cost = $57 Canadian including taxes -and they delivered it when it was done.

[MrMoMo]

Got it all back together and it seems to be fine, no draw off the battery and my running voltage appears to be around 13 (where it was before all this started)

I would reccomend to anyone at all mechanically inclined that this is a fairly easy teardown and re-build - and for the money saved compared to buying a new alternator - I would definately do it again. Removal is not that hard, and neither is dissasembly.

IIRC, wrenches required were;
8mm (battery posts and IC neg terminal)
10mm (B + post, vacuume pump, rectifier retaining nuts)
12mm (alternator belt tensioning bolt, small oil line)
14mm (alternator pivot bolt - need two for this)
19mm (large oil lines)

Also used a phillips screwdriver to remove the IC regulator and an impact driver with phillips bit to undo the 3 long screws that hold the alternator together - probably could have done it with a large screwdriver though. Flat blade screwdriver was usefull to help ease apart the front half of the casing from the stator windings (be carefull not to damage the windings!)

I did not go as far as removing the pulley from the rotor - my rotor checked out fine as did the slip rings and the main bearing so I did not feel it nessecary to seperate them

I probably could have handled removing and replacing the diodes, but it really didn't look like fun, and is something that could easily have been screwed with too much heat, so I didn't want to chance it when there are guys out there who do this all day. They did a very good job from what I saw, it appears that they steam cleaned it (or some other very thorough cleaning as it was filthy before and I could eat off it now) and they also re-painted my stator with a rust inhibiting paint.

So - if you are at all mechanically inclined - go for it!

Bruce

[jb welda]

sorry to hijack the thread but seems its run its course anyway and this was mentioned in the course of it:

whats all this about damaging your alternator by giving a boost to someone with your motor running? do you mean jumping a battery in another car with your engine running? how does that hurt anything please?

one love
jah bill

[MrMoMo]

If you charge a battery from your alternator it's OK, but if you try to START a vehicle from your alternator you can blow the diodes out - the surge of power drawn from the alternator can be more than the diodes can handle.

Usually it's ok because MOST of the power will come from your batteries, however, it is possible to damage your alternator doing this - same can happen if you try to boost a vehicle with frozen batteries while your engine is running. (frozen batteries are basically a dead short)

Best idea is to hook up the jumper cables, without your engine running - then try to start the other vehicle - your batteries should provide enough power. If not, start your vehicle and let it run for a while so that your alternator will help charge the other vehicles battery without depleting yours. Shut off your vehicle and try to start the other one. -As I said, most of the time you will be fine, you see people boosting while running all the time - but how many people don't realize that THAT is what killed their alternator?



Edit...
** Perhaps it would help more to realise that your alternator output (say 60 to 100 Amps) is no where near what your starter draws (likely over 200 amps) - does it make more sense now? There is also what is known as "inrush" current for the first split second you roll over your starter the current spikes much higher (can easily be double) **

[Pin_Head]

Usually two things kill diodes:
1) heat
2) excessive inverse voltage