Brought the car to the shop. The issue has been fixed. The replacement alternator was bad so it now has new alternator #2 in it. The car now has 12.7 at idle, much better. Now I have another problem, one of the axle tubes is starting to come out of the pumpkin (12 bolt). Smells like a nine inch swap in the spring.
That still isn't right. 13.8 is bare minimum to charge the battery. If you aren't seeing 14 volts on the voltmeter, you still have a problem.
Does you "Gen" light work now? Might be a bad bulb. If I remember right the bulb provides a voltage signal to the regulator.
With the alternator wired correct. When the alternator starts charging, it drops the ground to the bulb. Light goes off.
Problem is not the Alternator, man I tell ya,.......stop listening to dummy’s at repair shops and Auto store employees........you should show 13.9V. running...........
Yes, that's the problem lots of times. A fairly simple system. I was answering about the light. I could go back and read this entire post, but I'll ask. If he's running an old school external regulator, what was the output with a regulator bypass test? Where do you live Nick,? Wish I could get my hands under the hood.
Ok, so yesterday when I said it worked, on the way home from the shop I was reading 12.7 off the FiTech handheld which is better than the 11.3 it was reading before. As I found out today unfortunately this was temporary. We took the car out again and the issue seems to remain a problem. The attached image taken at a warmed up idle with the trans in park shows 11.4 on the handheld, 12V on the analog under dash gauge, and when I measured the voltage at the battery I get 12.2-12.3 (again, warmed up at idle). The voltage reading on the handheld and the analog gauge agree about half the time, with the analog gauge usually reading the same or higher than the handheld. When I crank the engine, the only one of the four idiot lights to come on is the one labeled "HOT". My arms and hands aren't small enough to reach behind the cluster unless I get on the floor, haven't tried that yet. I'm not at all against trying another battery, but I don't have another one to try and I've always believed that best practice is to diagnose, not just replace parts. I've asked in this thread before how to diagnose a bad battery. Speaking of diagnostics: I've attempted the test where you disconnect the regulator plug and jumper the red and blue wires of the plug and measure battery voltage but (and I know this is lame) I did not have a jumper with the right kind of leads to stay put on the wires while I checked battery voltage. As I previously mentioned, what I was able to do is remove the plug from the alternator, jumper battery positive to the field terminal, and I measured the battery voltage with the idle raised up somewhat. Measured voltage at the battery did not increase. My next step is to bring it back to the shop and I will have them try a different battery, I'll have them check the circuit between the regulator and alternator, and I'll ask about the GEN light. To answer Freakazoids other question, I'm in Worcester, MA.
Nick I would reach out to Chelmsford Auto Electric in Tyingsboro. They know how to repair old Delco gear. https://www.chelmsfordautoelectric.com/
I can’t explain how to diagnose the bad battery, but honestly it’s being diagnosed in the fact it doesn’t hold a charge and you keep telling yourself that it’s because of the charging system, when it’s not , it’s just a marginally adequate battery that is fooling with you IMHO.
Huh, I was thinking of this exact trick, but you beat me to it, with a nice photo to boot! Good work.
Yea, someone is going to start selling them. Theres some tricks to doing it, what Ide Say is right way.
Came back from the shop where they snuck it into their schedule to look at it again. I asked them two or three times to try a different battery. They put their analyzer/whatever on it and it tested good although it was a little weak when cold. They did not try a new battery since they their test didn't make them think they needed to. I won't repeat what I wanted to say when they told me that. They didn't do anything with the GEN light either. I have not found someone yet with a good battery I can borrow. Due to the big difference between voltage read at the battery and voltage read inside the car, I have another appointment to go back there mid October to check out the under dash wiring which they said is a bit of a mess, and they're right about that. On and on it goes.
Go buy a Battery and the electronic Voltage Regulator dude.........the difference between your readings in or outside the car is of zero relevance, and for the love of Mary and Joeseph why go back to the same knuckleheads that didn’t fix it the first, now second time? Take the Battery back where you bought it and get a New one...... you’re circling the tree.
Whatever a gauge wants it to be. Some gauges are junk when new some become junk when old. At the battery you should be 12.8- 13.2......With the car running at the gauge you should be at 13.9-14.1. If you show 13.9 + at over 1500-2000 RPM your charging system is working properly .
Should be nearly the same. Take a reading across the battery with the engine running, and from the back of the alternator to ground. They should agree with your voltmeter inside the car. With the engine running, it should be at least 13.8-14.5 volts.
As mentioned previously, the voltage measured at the battery while the car is running and idling is around 12.2 to 12.3. Inside the car it's low 11 volts. I will measure between the alternator output and ground. The regulator I have now is external, and electronic. The voltage gauge inside the car is part of a three gauge autometer set. It is only a couple years old. It does me no good if it is not close to what the battery voltage actually is. A 1 volt drop between battery voltage measured with a multimeter and voltage displayed inside the car is excessive. This is why it's going back to the shop, they're recommended highly around here. (And if Jim Weise is reading this thread, it's not THAT shop, this is a different one.) I will do what I can to try another battery.
A fully charged battery is 12.6 volts. Something is very wrong. The alternator is NOT charging the battery. I can't believe a shop would just let that go. My Autometer volt gauge reads within 1/10 of a volt from a direct measurement across the battery with a Craftsman multimeter.
Lots of good points and diagnostics in this thread. I'd like to add my $.02 for a few items. 1) Different gauges plugged into different parts of an automotive wiring harness are, 99 times out of 100, going to have different readings. Kinda like taking oil pressure readings at different place in the oiling system. Pick one spot, preferably directly from the alternator or the battery, and stick with it. Get a QUALITY VOM and consistently check voltage in the same spot. Your Equus or other parts house brand gauge isn't doing you any favors. 2) The original poster mentioned multiple times that his electrical wiring is a rat's nest. No surprise on a 50 year old vehicle. 3) He also mentioned that he has multiple add-on electric loads such as fuel injection which requires an electric fuel pump and has additional load from the injectors and the ECU to run it all, probably has electronic ignition, aftermarket sound system, etc. Each of these places additional load on the alternator, adding to the amp draw at all RPM. 4) Original equipment alternators on our classics suck at low RPM. There are several reasons but the main one is that they are seriously weak at low RPM and even at 1,500 plus most are rated at just 65 to 75 amps and that's on cars originally equipped with A/C. Late 60's units were rate in the 45 amp range! 5) It is entirely possible that the factory (or stock replacement) unit just cannot keep up with the electrical demand the car has now. For my money, bite the bullet and put a newer, high output internally regulated alternator on it. Do a real battery test. Be sure the battery is fully charged. Disconnect the battery leads, check the unloaded voltage and then put a load on it of 100 amps for ten seconds, let it recover for ten seconds. If it doesn't come back to within .5 to 1.0 volts of the voltage before the test, toss it and get another one. Cheap insurance and a good battery can be had for about $120 at most parts stores. The earlier advice about the idle voltage needing to be about 14.3 or better is 100% correct. That number is the target whether you have the system at as low a load as possible or with your high beams on, heater fan on high, radio on, etc. In as much as possible, straighten out the wiring mess. A messy wiring system can lead to all kinds of bad juju. I know we all have budgets but if the existing wiring is too bad go get a complete new harness from one of the many manufacturers like Painless. Some of them offer kits in stages (engine harness, front end, dash/instruments harness, body and tail light harness) so you may be able to do a little at a time. Please keep us up on what you find and the final fix.
