Alan

Doc,

Your test is still a reasonable one to do. Other failure modes might demand it - e.g. if the exciter resistor went open circuit the bulb alone might not be enough to initiate the alternator... the bulb would otherwise look normal.

(but of course in our case here it SEEMS it does not illuminate in bulb test mode).

Given that remote diagnostic data is not always 100% reliable (...!) I think its still well worth doing.

If with a direct batt connect to the initiation circuit it still does not generate at idle - its pretty definite.
It seems since it can generate at high rpm - changing the regulator & rotor brushes is a likely good solution for this - and fairly cheap.

I am not convinced high output alternators are very worthwhile - many have a higher max output at high rpm but actually a lower output current at idle rpm. In asking for full characterization at low rpm I have been unable to get hard data to convince me otherwise from any supplier... Given some of these are more than 2x the cost of a new Bosch - I want to really know that what I'm getting is valuable to me. Rebulding the Bosch will likely get you a little more current and then these can be boossted a little with some smple component swaps - I'd go that route...

Alan

Alan

But then it would still illuminate in bulb test mode....
No - only the original one - apparently tested twice by incompetent idiots...

I agree do all the tests you can to narrow down - including Docs proposed test - and of course we can't always rely on all results given being fully accurate - but they do seem to tell a clear story...

Alan

docmirror

I once had a VW with one of the first solid state alternators. After the mileage got high, the charge light would stay on until I drove it a bit. I knew it needed brushes but I was too lazy, so I just kept driving and revving it to make the light go out. I figured after having to rev it to about 4000 that I should go in and do the job. When I got the bottom brush out, the only thing left was a smidge of the spring and a dangle of the copper wire! I was amazed the regulator diodes didn't fry, but I never put much load on it.

I'm also not a fan of over size alternators. The job to be done right should change all the primary charge lines to support the higher amperage. This is particularly true on the 928 where I've seen several cars with burnt charge lines from the alternator to the jump post, and also the hot post on the drivers side near the PS reservoir. I suspect the charge line to the jump post takes special duty when the car won't start and is jumped from the post, and not the battery terminal.

IndyMatt

1. Test failed. Connected the speaker wire and it didn't do anything different. In other words no charging.

2. The blue wire did have cracks in the insulation but the wire underneath was still good. This was right at the 12 pin connector. There was enough wire to cut, solder them back together, then melt some heatshrink around the new joint. This was the wire that goes into the number 1 socket. Let me reiterate that the wire was still good just cracked insulation, which is now good.

3. Wally there is only one alternator that was tested at two different shops. Once at Advanced Auto where I didn't feel like the guy did a decent job of testing. Next was at Vans Electric where they rebuild alternators and they didn't test it any better than Advanced Auto.

4. Ordered a new higher output alternator from Dominick Irragi. Should fix the problem and it sis going to be putting out 200 amps. Look for a group buy presented on here by Roger.

IndyMatt

Irragi Alternators are well known for their quality. Alan, I would look these up on the net. He has been building high output alternators for the audio competitions for years. He specializes in increasing the amperage output at low RPM's since these cars are at idle with their systems blaring for hours!

docmirror

Ok, new alt time I guess. Funny the shops report it as good.

mark kibort

you probably have a broken winding. a brand new rotor costs around $50. once it is installed, you have a new rotor. any alternator shop can do this for you. I also had them bolt on a larger diameter pulley to slow it down a bit.


mk

Alan

That may work OK for you racing around & around at high rpm - for Matt - I think a smaller pulley might be better to speed it up for idle performance with big audio - different application..

Anyway he will soon have a new alternator...

I did try to check out Irragi - seems like they have some satisfied customers - but I don't see any data on the alternator specs - except a max Amps number.

I'd really just like to see someone post an rpm vs current & voltage chart - simple stuff - what current can it sustain at idle rpm at regulated voltage (whatever it is but say ~13.5v-14v), and what current can it sustain at idle rpm at at least 12.7v (minimally charging voltage). These numbers will be far lower than 200A for sure...

You of course do have to figure the engine idle crank rpm to alternator rpm which varies by year due to crank & alternator pulley size changes.

If they can offer a smaller than stock alt pulley I'm fine with using that to help boost alternator idle rpms... (but I draw the line at having to change the crank pulley - too much work).

Alan

ew928

rpm vs current/voltage vs TEMP chart would make me happy.
My alt. seem to not like summers.

An alt that runs fine in the shop but chokes when it's 90+ out and stuck in traffic just sucks. When you need the voltage most, it least performs.
HVAC in max cool is bad enough a draw, then the double cooling fans kick in . . .

Alan

Ernie - good point - lets just have all that measured at 150F.

Maybe lower would work for some of you - but I drive at ~120F ambient

Thats outside the engine bay....

Alan

IndyMatt

I read somewhere that his 220A unit at idle was putting out 105 amps or something like that. Not sure of the temperature. I think he does use smaller pulleys with some applications. I will let you guys know how it performs once it is on the car.

IndyMatt

Al right haven't posted in awhile since going off to Iraq for six months. Basically the new alertnator is on the car and there is NO CHANGE! I am at a complete loss on this thing! I think the next step is ordering a new/gently used wiring harness for the alternator. I have no idea what is causes this and it is driving me nuts! This will be a top priority as well as getting the transmission rebuilt when I get back in November. I want to be able to drive the car reliably!

Landseer

Before you do that, disconnect alternator and trace each wire with a voltmeter and long extension wires if needed, back to the proper plug on the fuse panel and to the battery and starter. Manipulate those wires and see if there is a break. Should be obvious if the failure is so complete. I know that you have done some testing, I'm suggesting a deeper dive.

Jadz928 and I did this trace on an 86 and it was very valuable. And its not brain surgery.

Do you have wiring diagrams to help determine exactly the routing path and test node possibilities? If not, one of us can read the diagrams and tell you what to test. Got to go to work now, will check back later. I'm talking walking each wire from end to end.

Methodical, with pictures for us to see the connections to the starter, alternator, 14 pin connector (wrong sequence inside the plug maybe?}. Something is wired wrong, you need to be careful.

This has been a problem for you too long, pictures / more inputs will help the heavy hitters on this thread to solve this for you.

Mrmerlin

I would go to the hot post and inspec all of the wires there (includes opening the back of the 14 pin connectors and looking for broken wires or insulation), Disconnect the battery first.

And one other thing, what was the last thing you fixed B4 the alt started n ot functioning??

WallyP

I would start at the heavy red wires that carry the alternator output to the starter solenoid, then go to the medium-sized red wire that carries all electrical power to the jump post and then to the car.