I have a Cornwell branded multimeter I'm using. The underdash gauges are AutoGage. Both times the alternator was replaced, I was told the previous alternator wasn't charging the battery. The car made the first outing with the new alternator showing mid 12s on the in car gauge at idle, and on the next outing it dropped back down to low 11s at idle on the in car gauge. Can an overloaded alternator act this way? The EFI is a throttle body unit so it's not like a multi port system with rails with multiple injectors. There is the ECU and the electric fuel pump. It has an MSD ready to run distributor, (no 6AL box or anything like that), no aftermarket speakers or anything. The trans is a 200-4R so there is also whatever power demands the lockup converter has. I've been eyeing the 150A 12SI Powermaster units Summit has. That will probably be more output than I'll need, but I would like to rule out other problems first before I start making upgrades.
*Properly* functioning alternators will only output as much power as is necessary to meet the demands on it at a given time. Within reason, it's not really possible to get too big an alternator.
I will continue to advocate that you reach out to Chelmsford Auto Electric or similar shop slightly closer to you. No fun to have a car you can't drive.
I think you have plenty of Alternator, a new Battery combined with a cheap electronic external Regulator and problem solved. You basically can’t afford a new Battery but can pay knuckleheads at a shop to throw parts at your car? Oh the Humanity.....
The car starts and drives fine. I did see that suggestion, earlier, thank you. Chelmsford is a bit of a drive. As mentioned earlier, there is also an issue with the rear end in the car that I'm dealing with in parallel to these electrical gremlins. I'm trying to drive it gingerly and avoid longer drives until I get that squared away. If I find a similar shop nearby I will look into it. Is this a complete sentence or did you mean to include an "if" in this phrase between "think" and "you"? It changes the meaning if you did. I've said it at least twice already in here, the regulator I have is an external electronic one. Guess what I did this morning? I took the battery out and brought it to the parts store where it came from. I was lucky enough that it was new enough they were able to replace it under warranty. Once the smoke has cleared after you've read the previous two sentences, this is how it went: with the car fully cold, I put the new battery back in the car and fired it up. I measured the voltage with the multimeter at the battery and it read 13.9V. It's a new battery, I would expect to see that. The handheld read 13.2 or so volts and the analog gauge read about 14V. I let it sit there and idle, and over a couple minutes I slowly observed the battery voltage on the multimeter drop from 13.9 to 13.7. I also ran Larrys test above and checked between the alternator output and ground while idling. 14.5V. I shut the car off, and did other things for a couple hours. Started the car up again to take it for a ride to see what it did. Right after the second start I immediately notice the handheld is now displaying 12.7 or so while the car warms up again. Analog gauge reads maybe 13.5. I take it for a drive. Cruising around town at 30 mph or so the handheld reads 12.6-12.7. The analog gauge reads in the 13s. I get to a red light and the handheld displays between steadily between 11.6V - 11.8V. Analog gauge reads mid 12s. Previously at a red light it was 11.2V - 11.3V from the handheld and around 12V from the analog gauge. I got the car back home, now fully warmed up, and repeated Larrys test checking between alternator output and ground. I get 13.6V on the multimeter. The meter reads battery voltage around 12.6 or so. So getting a new battery was a marginal improvement, but not enough to say anything was fixed. I'll say it again for emphasis: I HAVE A NEW BATTERY AND AN ELECTRONIC EXTERNAL REGULAR AND IT DID NOT FIX THE PROBLEM. Happy now? You know something, I had quite a few not so nice responses and four letter words going through my head when I saw this but I'll refrain. Please understand that while a battery swap worked for you, it didn't fix anything for me, and I expected that to be the case. This is why I was happy to bring the car to the shop so someone more skilled than me could diagnose the problem. With these old cars, every cars electrical situation is different. Identical symptoms don't mean identical problems. I have not asked anyone to "throw parts" at the car without diagnosing it first. Nor have I replaced anything myself without believing I had to. My next step is to look at the connections at the starter motor/solenoid.
My remarks aren’t aimed at you personally, but more toward idiots that pose as experts at shops around the world, they don’t know old cars, they know machines and computers that tell them what parts to throw at it, and more times that not they see the car again at the customers expense. Sorry you feel offended by my remarks, but your car now starts and drives and hasn’t left you stranded yet right? like before? Which means an improvement. Lastly you need to check the battery cables and the 2 grounds, one on the battery and the one from engine block to firewall, and cables should be #2 in size for optimum performance. A poorly grounded system won’t charge properly. I believe you problem isn’t just 1 big thing, it’s multiple little things and that’s why it’s confusing.
Nick, Your problem is very confusing to me. The differing readings seem to be most noticeable with this handheld controller. Is it possible that the problem is there? Does the system modify voltage in any way? That would be my first question to their tech help line. The main readings across the battery and from the charging post of the alternator to ground are the important readings. If this was my car, I would not waste my time with the old externally regulated alternators. They are so inferior to the cheap and widely available 10 and 12SI series alternators. The old alternators are notorious for low output at idle. You need an upgrade or you will continue to have low output. Not sure I understand your reluctance to upgrade. You have probably spent more money with mechanics than what it would cost you to get a good 94 amp 12SI. The conversion process is so easy to do.
Here is a breakdown of the charging system from the Buick service manual. https://www.teambuick.com/reference/library/71_chassis/files/68-c.php The last frame has the wiring diagram isolated. I am still thinking that the "Gen" light not working is the source of your problem. What is the voltage to the "F" terminal at the alternator? With the key on engine not running. Should be above 5 volts to provide the initial field current. This turns the alternator on. You also mentioned the the under hood wiring is a mess. I would strongly suggest the you consider replacing the harness. They are not that expensive, especially when you are paying someone to troubleshoot faulty wiring.
Looks like voltage loss between the alt pos post and the battery. 14.5 vs 13.6 High resistance somewhere in that circuit. Also run volt test from battery Pos to alt ground post to see if there is any difference. You could try adding a wire from the alt post to the battery Pos and see if the battery voltage will gradually rise.
The average age of the cars at this shop I would guess is 50. It's a large part of their business. The car left me stranded once and has not done so again since I replaced the plug that goes into the regulator. I agree with this, but previously it sounded like you held the opinion that if I just replaced the battery that would be the end of it, and it has shown that is not the case.
Welcome to my world. Good question, and not that I'm aware of. I will ask them tomorrow. It's not that I'm reluctant to do the upgrade, it's just the fear of the unknown. It has always made sense to me to make sure you have a good foundation before you start making upgrades. The best way I can describe the way my mind is looking at it is to make a mechanical analogy: It's not smart to put a supercharger on an engine that you suspect may have a head gasket problem, especially if you don't know how to diagnose a bad head gasket. Is making the upgrade to an internally regulated alternator going to exacerbate any of these problems I'm dealing with? I don't believe so, I just would like to know what I'm dealing with, because I'm just as confused as you are. Having these wildly different voltage readings inside the car is a WEIRD problem. Maybe my thought process is totally wrong. I'm just trying to avoid making anything worse by upgrading prematurely.
Well if that's the case and the original wiring is such a mess, I would replace the wiring harness to eliminate that factor.
This is useful, thank you. I will check it tomorrow. Does the cluster have to come out to change that bulb? This is a photo of the back of the cluster from one of these cars: The idiot lights are in the gauge in the right. I'm assuming I'm trying to reach the lower one of the three black things on the gauge in that photo? Twist out or pull out? How long does this normally take to do for an unmodified car? It will take longer on my car because of the MSD distributor and fuel injection. If that's an all day job I'm looking at $1,000 in labor. I agree it's probably a good idea to do it but I would like to avoid that job if I really don't need to.
I could only do this test by taking the plug out of the alternator. With the key on and measuring between the field terminal on the plug and ground I measured 11.67V. You said this should be at least 5V. Can it be too high?
The FiTech rep didn't have an explanation, nor did he suggest anything new other than to check for a firmware update on the handheld programmer. Did that, it's up to date.
I'm curious if you resolved this problem ... I'm having similar issues with mine and it really is frustrating. I have no add on goodies to draw power. '71 GS 455 with all new wiring harness underhood - I'm about ready to go with the internal regulator set-up but I'd like to know why this problem exists. It seems like it should be simple.
I just this week had a brand new engine harness put in. Last fall I had an internally regulated powermaster alternator put in. The shop did it as a one wire installation. I haven't really studied the voltage readout on the FiTech handheld compared to the analog underdash voltmeter yet since I just got it back yesterday from having the harness put in, but on the analog voltmeter it was last showing about 14V driving around town. So at the moment, I don't believe there is any real low voltage issue.
Just got back home from putting gas in it. There is now no difference between the displayed voltage on the FiTech handheld and the analog voltmeter, so whatever the issue was was fixed by swapping the engine harness. I'm calling this problem resolved.
