[Ben M.]

We've got electrical people here... I'm curious on this one and no one else seems to have a clue.

Working on a 1989 Cadillac Brougham with the Olds 307. The alternator wasn't charging when I got it. It's a CS130 alternator with a battery cable directly off the output stud and a single brown wire on the L terminal (this is how Cadillac did it from the factory in '87-92 per the factory service manuals). Simple investigation found the charging light in the dash was open (brown wire). Took dash apart and found the bulb socket was broken. Replaced it with a new one and verified that the dash light now works, +12V on the switched side with the key on, +12V on the brown wire out at the alternator with the key on engine off. Turn car on, battery charges because alternator is now working as it should (14.2V out).

Problem is, the charge indicator lamp in the dash never comes on under any circumstances. I ground the brown wire out at the alternator side and it lights up. I measured the resistance of the L terminal at the alternator to ground and it measures 600Ω with the car off. This seems to be a little high as the terminal should be close to ground as it has to pull 250mA through the bulb and 600 ohms is going to pull less than 1/10 that and I doubt the bulb will ever light up at 20mA. The factory service literature for the CS130 doesn't mention this situation and no one else seems to have experienced something similar either.

Since I don't want to just "trust" that this is going to stay good all the time and leave my teenage daughter stranded somewhere one day, I'd like to fix the indicator to make it all work as it should. Should I just go ahead and swap in another parts store rebuild (this one is from May the previous owner bought)? Or just splice in a 350 ohm resistor in parallel with the bulb and call it good? I don't like cars not having functioning warning systems. I'll probably do the 350 ohm resistor modification just to ensure it's always going to charge, but I really want that warning light to work.

Anyone seen something like this in their time with the CS130 alternator? I know it has a much more complicated and "smarter" regulator circuit setup than the 10\12SI units so something being damaged or off internally is possible, I just can't find any confirmation that someone else has had the same problem.

[stellar]

I would try another alt, or have that one tested. It may have a bad reg or the wrong reg in it.

[Ben M.]

Been working on this some still as the car stopped charging shortly after this post and hasn't charged since. Apparently Cadillac put a diode in series with the charging lamp indicator circuit to protect against the field of the alternator turning the charge lamp on while driving. That diode is completely blown out on this car after I dug it out of the loom behind the brake booster. I still have a 400kΩ high impedance that can't be explained between the leftovers of the diode and the charging lamp in the dash. So I have to dig out the wire and trace it all the way back to the dash and replace where it's gone bad. Fun! The impedance between the alternator plug and the other half of the blown diode is 0.1Ω so at least that part of the circuit is good still.

I think a previous owner idiot hooked the battery up backwards and caused some electrical problems...

[John V.]

My brand new '80 Pontiac Phoenix SJ had a short of some sort from new. Occasionally the optional Heavy Duty Battery would be dead and I'd have to jump start it which it always fired right up.

On this particular day, my wife was following me in her car to the dealer so they could fix the short. Along the way, it stalled at a stoplight, I don't remember how or why.

But now uber mad and frustrated, I jumped out of the car, had my wife pull alongside, grabbed the cables, popped the hoods, and hastily went to hook them up.

In my rush, first and only time in my life, I crossed the cables and saw a spark.

I got it started and completed the drive without further incident.

They fixed the short wherever it was and that was covered under warranty.

But I was told the diodes blew in the alternator and that repair was on me.

Needless to say, I was ticked at myself and never made that mistake again. Every time I hook cables up since, I take my time and double check for the positive and negative battery posts.

Your post reminded me once again of that long ago screw up!

Good luck sorting it out..

[Ben M.]

The conclusion to this little saga was reached today...

What's left of the diode once I found it buried in the harness:


Cleaned it all up:


Started pulling the harness apart to trace...


Found this buried inside:


Somebody had cut the gauge cluster lamp wire back and then added a splice to the other side. This splice ended up over at the plug for the EGR solenoid, to provide a very weak +12V through a bad diode. I guess the lamp in the dash died and rather than fix it, someone decided to splice a switched +12V onto it. Kind of a terrible way to do it...

Handy alligator clips to bypass the entire mess:


Imagine my surprise when the light started working again!


My woes weren't over as the remanufactured alternator I had purchased ended up being bad out of the box. I had to troubleshoot it for 6 hours to determine that, and then the parts store manager accused me of lying and re-tested it 3 times on their new test stand (failing all the while), then denied me a refund, but that's a story for another thread...

Fortunately everything now works with a working alternator:


Not my best work, but it's now spliced together and fixed properly:


I have to locate a diode to replace the failed one, probably a 1N1001 or something similar will be overkill. I know no one out there gives a crap about these cars, but I figure this will help someone out who is pulling their hair out over a similar charging problem that nothing seems to be working on. And to relate to Pontiac-land, this engine and charging setup is almost 100% identical to the '83-86 Pontiac Parisienne with the 307, and is identical to the '87-89 Pontiac Safari, so someone in our corner of the world may have the same problem.

[BB70]

Good work Ben and nice to see your determination to get at the root cause. When you find a hack like a scotch lock you wonder what else is going on. Also, nothing like a new defective part to make you retrace your steps a few times. Been there.
John

[mgarblik]

That's some good troubleshooting there and the root cause found. The high resistance without an actual open in the circuit was the big clue. When I worked at the new car dealer, anytime we found a Scotch Lock in a harness 2 things happened. 1. The repair was no longer a warranty job. 2. The repair went to hourly, real time customer pay at a higher labor rate. A poor line tech can lose their butt chasing hack jobs like that. These crazy problems always have a simple resolution. Finding it is the tough part. Any time I see a Scotch Lock, I begin to twitch and know it's going to be a long day.

[SRR]

I'm telling you, call the District manager about that. Your too nice a guy! Tell him your professional back ground and how you were in not so many words accused of being a liar.

[Ben M.]

I agree, the worst part about these cars is how much of a pain it is to get to the indicator lamp sockets (trim to cluster in dash and glove box have to come out to get the dash pad screws out) and when I pulled them, only one was still good (the brake light). The bulbs themselves were good on half, but the sockets themselves were all corroded and snapped apart so I had to order brand new ones. I ended up replacing them all just because why not? I know it's a throw-away car but if I didn't fix it right I could easily see getting a phone call at midnight with the kiddo having a dead battery or car that wouldn't start and me needing to go get her, so I'd rather not have that.

The guy I got this thing from told me his step dad got it from a little old lady and he "got it running" which judging from the looks of all the screw-ups I've had to fix, he didn't do much to it other than put new tires on it and put a new battery in it. I reinstalled the accessory brackets to get the AC compressor belt on it again as post '85 307s are notorious for having belt squeal and alignment issues when the compressor or smog pump are left off. Fortunately other than the new sockets and new belts to replace the cooked ones, I haven't spent a dime on this car beside the cheap cheap purchase price.

Originally Posted by SRR

I'm telling you, call the District manager about that. Your too nice a guy! Tell him your professional back ground and how you were in not so many words accused of being a liar.

Yeah, I'm just going to let it slide. I'm going to take it back to another store and get them to handle the return. Most of my experience with bringing up poor employee\manager behavior and explaining my professional status ends up with the person I'm talking to siding with the jerk employee or blowing me off, so I'm not going to waste my time. I'll return to the local AutoZone and give them my business and this place can go under for all I care. Shame as I had a nice rapport with the older guys who used to run it a few years ago (first name basis, always asking what projects we were working on today, etc), but they don't seem to be there anymore as I haven't seen them in over a year and the new guys are all tat'd up clueless biscuit heads more interested in their phones or listening to the radio than helping customers (I sound like a really judgmental old person now).