Alternator help for 1992 2.5L turbo (Lebaron GTC)

[thrashercharged]

My alternator started going intermittent on my drive home from work. Alternator would stop charging (volt meter went down, lights dimmed, etc.) for maybe 30 secs to a min or so, then I'd hear the belt squeal indicating that the alternator was starting to charge again and start loading (causing the belt to squeal - I know, the tensioner might be getting weak or the belt is getting old and glazed too) and the belt would eventually grab and I'd get a working alternator again. This cycle would repeat and I made it home. No, my problem isn't just a loose belt - the belt is tight and turning the alternator, but on occasion the alternator will just completely stop charging and go into a no load state.

First question - apparently I could have either a Bosch 90 amp, or a Denso 75 or 90 or 120 amp? 4 options for the same model year and engine? Is that right? And none interchange, I have to get exactly the right one?

Second question - the field has to be excited for the alternator to charge, so I'm wondering if this is really an alternator problem, or do I have a wire to the field that's intermittent and causing the field excitation to come and go? I have parts of the service manual, and the field is connected to +12v on one side (through the ignition switch) and to the Engine computer (through something labeled K20 - perhaps that's circuit K20?) on the other. What's the engine computer's role in this and how do I check out that it's doing it's job?

I'd like to verify that I don't have any problems with exciting the field before I throw and alternator in there. I did a search and although there are lots of posts about alternators, I didn't find anything that really answered my questions or applied to the 1992 model year. Any help or advise would be appreciated!

Thanks - Tom

[135sohc]

If the alternator has a large cooling fan blade on the pulley side, outside the case it is a bosch alternator. The denso ones are more compact and have the internal cooling fan. Both are interchangable to a large degree. Especially on something as late as a 92 since chrysler had finally standardized the tensioner setup. Most here consider the denso a better unit (its a japanese unit and lasts just about forever) if your replacing a bosch unit.

It is very possible to have a loose field wire connection or one that has corrosion formed on it. Those can cause intermittent charging.

[turbovanman²]

The Nippo is preferred, smaller, lighter, last forever, look like it should be on a Honda.

As for testing, you need an amp meter to properly diagnose but basically you disconnect the field wires, then put a + wire to the top terminal, then ground the bottom one and this will full field the alt, don't do it for too long, if it you get max amps and voltage, then its good and you've probably got a bad SBEC. You also need to check the diodes as it can still charge but have bad diodes.

Get the biggest Nippo you can.

[csxtra]

Hi Tom! Glad to see you on here, but sorry to hear you're having issues.

Yeah, the alternator is controlled by the engine computer (SBEC is the term for the '92 models). If you can't localize the problem to the alternator using Simon's method above and the problem is actually in the computer's voltage regulator, most folks either retrofit an external regulator or have a Nippondenso alternator made with an internal regulator.

[thrashercharged]

Hi Warren,

Yep - the Lebaron is my DD now, 80 mile round trip on a 2 lane highway - I like the fuel economy and it's quick enough to pass people (all stock except for the glasspack in place of the cat that fell apart and no other muffler) plus it's fun to drive being a manual. She’s been doing pretty good so far with almost no problems except for the instrument cluster going crazy sometimes with very little maintenance. I try to limit it to good weather though or she'll just totally rust away (rockers and quarters already had holes if you recall.) so it's time to park it for the winter.

But, I got caught in our first snowstorm a couple days ago and had to drive home in a blinding snowstorm, took me 2 hours to drive 40 miles. I tell ya, these cars are not meant for winter driving. I literally skated home. The hidden headlights act as a cup to scoop in snow. And to top it off, the last 20 miles my alternator started going out.

So – the SBEC must ground the field, so the test is to basically check to see if I have +12v on one of the field terminals, and to ground the other one to see if the alternator starts working?

So this alternator doesn’t have an internal regulator? I’m not quite getting how the SBEC acts as a regulator too? I can see it providing the ground to excite the field, but from what I recall from the diagram in the service manual the SBEC isn’t on the output side is it? Maybe the better question is – how do I retrofit an external regulator?

As for the body and rockers, apparently replacement rockers and quarters aren’t available in the aftermarket, and good donors aren’t anywhere to be found around here (probably all in Arizona and Calif). Does anyone know if the later (’93 and newer) Lebarons (that don’t have the hidden headlights) have rockers and quarters that’ll fit mine? They’re a bit more plentiful in the yards so I might find some with good parts.

Thanks,
Tom

[contraption22]

Hi Warren,

But, I got caught in our first snowstorm a couple days ago and had to drive home in a blinding snowstorm, took me 2 hours to drive 40 miles. I tell ya, these cars are not meant for winter driving. I literally skated home. The hidden headlights act as a cup to scoop in snow. And to top it off, the last 20 miles my alternator started going out.



Off topic, but heck it's your thread and you brought it up! LOL

These cars are absolute beasts in the snow with winter tires. Good winter tires on some spare wheels will make your car nearly unstoppable in snow that's not to deep to push the car up off the road. And they cost less than an impact with a guardrail, or another car.

[turbovanman²]

So – the SBEC must ground the field, so the test is to basically check to see if I have +12v on one of the field terminals, and to ground the other one to see if the alternator starts working?

So this alternator doesn’t have an internal regulator? I’m not quite getting how the SBEC acts as a regulator too? I can see it providing the ground to excite the field, but from what I recall from the diagram in the service manual the SBEC isn’t on the output side is it? Maybe the better question is – how do I retrofit an external regulator?


Thanks,
Tom

Sorta, one has power, the other one is grounded by the computer to control the charging rate. The big thick output wire has nothing do with the SBEC, just the 2 little ones.

http://www.turbo-mopar.com/forums/showthread.php?18614-Info-or-source-for-a-non-computer-controlled-regulator-2.0-2.4&p=213810&viewfull=1#post213810

[supercrackerbox]

First thing, check the condition of all the wires and connections to and from the alternator. I've seen the power wire at the alternator connection get melted, I've seen the large bullet connectors behind the battery fall apart from corrosion, and I've seen the field wires get oil soaked and burned through. All the new alternators and voltage regulators in the world won't help you if your cables are shot.

My Daytona, even though it's very heavily optioned, only had the regular Bosch alternator. To my knowledge, the 120 amp ND only came on V6 cars. I got one of those alternators from a junkyard and it bolted straight on with no modifications except swapping to a 4-cyl ND pulley. V6 cars had a 6-rib belt, 4-cyl cars have a 4-rib belt.

[turbovanman²]

V6 cars had a 6-rib belt, 4-cyl cars have a 4-rib belt.

TIII's have a 6 rib too, :eyebrows:

[marc]

You said you hear the belt squealing right before it comes back online, well If you can hear the belt squealing, its loose. Sometimes a belt can slip without making any noise. You would not believe the number of times I have seen good mechanics condemn the alternator for a slipping belt!

[thrashercharged]

You said you hear the belt squealing right before it comes back online, well If you can hear the belt squealing, its loose. Sometimes a belt can slip without making any noise. You would not believe the number of times I have seen good mechanics condemn the alternator for a slipping belt!

I wondered about that, but it seems tight and the tensioner seems good. But remember I'm running at 1500-2000 RPM when the alternator load disappears and reappears, so I'm thinking the belt squealing is normal because I'm dumping full load on at 1500-2000 rpm. When the alternator quits charging it's not because the belt is slipping.

I checked and I have the Bosch unit. Wires seem to be in good condition. Since my alternator works 50% of the time, I'm thinking I should probably just run the engine and see if the alt works. If it does, I'll just let it idle (or drive around the block) until it fails, and then check to see if my field has a good +12v on one side and if the SBEC is grounding the other. If the field wires check out ok, then the alt is bad, right? If I find that the SBEC isn't grounding, then I could wait (while monitoring) until the alt works again, and see if it's because the SBEC grounds the field again. If I find it's the SBEC's fault, I could pursue the external regulator route. Does this sound like a valid plan?

[black86glhs]

Belt squealing is not normal. I'll bet the belt tension needs either a little tweaking or it is glazed and and will cause it to squeal even if properly adjusted.