Battery not charging - tell me what I'm missing

[doodah man]

Ok, this will be a long story. If you're not into long rambling stories, skip to the bottom for a concise summary.

We left Philadelphia on Friday on our way to Tichonderoga, NY for a friend's wedding party. There was a crazy thunderstorm about 60 miles south of Albany that lasted about 10 miles. We were running the AC/defrost, wipers, headlights and flashers. We just made it to Albany when the truck started to miss and sputter. I babied it to the nearest exit and it died at the first stop light. The battery was completely dead. We have AAA+ so we had 100 miles free towing and our destination was 97 miles away. Figuring it would be easier to work on there in the morning, we rode the rollback the rest of the way to the wedding. The next morning I pulled the battery and alternator and took them to a Napa for testing. Battery drained but OK, alternator "possibly" bad (the guy there wasn't sure he hooked it up right. Yeah, I know, "What?"). They didn't have a replacement anyway, so I took it over to Advance Auto. I had them test it again on their machine. It came up good (putting out 14.4 V) twice in a row. So I charged the battery and put everything back together. It started right up and ran fine on a 30 mile test drive. So we enjoyed the rest of the party and headed out Sunday morning for another friend's house in Chatham NY (~100 miles away) and had no problems on the way including a few stops and starts. Monday morning we got an early start for Philly, but stopped at a gas station in Chatham for coffee. When we tried to start it again the battery was drained. We got a jump and made it back to our friends house. I borrowed a car and picked up a new battery (the original one was 8.5 years old) and a volt meter. The battery read 12.6V when I installed it. At idle, the voltage at the battery posts was 12.3V and the voltage at the battery terminal on the alternator was 12.3V. I was expecting something like 14 V. I was able to track down an alternator locally and installed it in the parking lot of Chatham Auto Parts (That place was an old school independent parts house. Awesome.). The guy at the parts store had a tester that showed no voltage change with the new alternator (still about 12.3V). So I put the old one back on and drove 15 miles to Hudson to get a new voltage regulator. I put that on (used the old condenser) and still no change in the voltage at the battery. Drove the 240 miles back to Philly without turning off the motor. The battery was 12.0 V when I parked in Philly.

The only other thing I noticed is that it seems to be running a little colder than usual (maybe 10% or so). I figure that is unrelated and maybe just a thermostat that needs replaced. Also, the alternator belt did break about a month ago.

Now I'm lost. I never tried cleaning contacts on the alternator plug. Will try that after work today.

Here's the summary of what happened and what I've tried to fix it:

1. Truck died after about 250 miles of driving including one soaking T-storm that required heavy use of accessories. Truck would not crank and accessories barely worked. Battery was drained.

2. Battery tested ok, alternator tested Ok: putting out 14.4 V.

3. Charged battery, reinstalled alternator and drove ~120 miles with at least 6 or 7 stops and starts without incident. The only weird thing was that the engine temperature was consistently lower than before by about 10%. After several normal starts the battery was drained again and required a jump start.

4. Picked up new battery (12.6 V off the shelf) and 12.3 V at battery and alternator battery terminal with the engine at idle. I expect 14 V.

5. Installed new alternator. Still 12.3 V at idle.

6. Put old alternator back in and replaced the external voltage regulator. Still no change. 12.3 V at idle.

7. Drove 240 miles back home without shutting off the engine. Battery at the end of the trip measured 12.0 V with engine off.

Any suggestions for other diagnostics or ideas why this thing won't charge?

Thanks in advance.

[RustedMetal]

Sounds like a ground issue, terminals or wire itself. If it were mine I would replace all of it with new 1/0, new ring and battery terminals and new grounds. I like using welding cable.
Posted via Mobile Device

[chiefcfd]

Maybe a loose belt. Never hurts to check. Make sure it fits the pulleys correctly too.

[70-K5]

Originally Posted by RustedMetal

Sounds like a ground issue

That was my first thought too.

[doodah man]

Originally Posted by 70-K5

That was my first thought too.

Is there a specific ground that's associated with the charging the circuit? I just replaced all the ground straps this spring. I will check them all again for tight. The voltage regulator is grounded to the core support. I guess this is also the ground for the alternator so I'll start there.

[chevy_mike]

I ran into this problem on my '65 C10. We found a wire that connected to the ignition switch, that looked okay, had broken internally and when we brushed up against it, the insulation finally let go and we could see the broken wire. We reconnected that and all the charging issues went away for the 3+ years I owned it.

Try gentally pulling on the wires connecting to the ignition switch and see if any come loose.

[MARKDTN]

Sounds like a bad ground or wiring issue between alternator and battery.

Unless you are a purist, I would replace the alternatorand separate voltage regulator with a SI alternator from a 70's vehicle or even better a CS144. Then I would be sure you have a good ground from frame to engine block. With the newer, bigger alternator I would run a dedicated wire from the output terminal of the alternator to the battery. The bigger alternators do not work well with the factory ammeter, so you may have to bypass it. If you leave all the other factory wiring intact, you can leave it, but it may not be accurate.

http://67-72chevytrucks.com/vboard/s...d.php?t=425762

http://67-72chevytrucks.com/vboard/s...d.php?t=579118

[RichardJ]

To check the ground connections use the volt meter with the engine running. Check the voltage from battery negative post to engine, negative post to frame and negative post to regulator frame. You should get 0.0volts or at most a few tenths. A bad ground or an open ground will read several volts or higher.

The wire from the ignition switch can be checked with your volt meter. Pull the plug off the voltage regulator and with key ON, engine OFF there should be battery voltage on the pin #4 wire in the plug.

It is not really a good idea to solve an unknown problem by introducing a new variable such as a new charging system. You may end up chasing two problems instead of one problem.

The existing wire from Alt to Battery serves as the shunt for the factory Ammeter. It is effectively, part of the Ammeter. Changing its length or gauge will change the Ammeter.

[doodah man]

Ok, I did a little more poking around with the volt meter.

The ground measured as suggested by RichardJ was good at engine block, frame and voltage regulator mount was good.

Measured no impedance from battery + terminal to batt terminal on alternator

With the ignition switch in ON position, I got 12.5 V on the blue wire (field) on the 2-wire plug that goes into to the alternator. Next I followed the test procedure in the service manual for the field circuit.

1. 12.5 V between plug terminal 4 (ignition) to ground.
2. 0 V between F terminal on plug and 4 terminal on plug.
3. 12.5 V between 4 terminal on plug and alternator.

These tests indicate that the problem is the blue wire between the F terminal on the regulator plug to the F terminal on the alternator, but I'm getting 12.5 V at the end of the blue wire. Could it just be the connection?

At the suggestion of a friend, I put a jumper between the battery + to the Field F terminal on the alternator to bypass the regulator and ignition wiring and test the alternator. I still got 12.5 V at the batt terminal on the alternator. This leads me to believe that the alternator is bad again. Is there something else?

Thanks.
Posted via Mobile Device

[truckdude239]

if i was you i'd swap over to this style alt its the same price as the r old style and more dependable

http://67-72chevytrucks.com/vboard/s...d.php?t=119379

[VetteVet]

Disconnect the plug at the alternator and measure the voltage at each wire with the key on and off. White wire S/B 12 volts key on zero volt's key off.
blue wire S/B 12 volts key on and off. The white wire is the alternator exciter wire and it has a resistor inline, either a wire as mentioned or the idiot light if it's not a gauge dash. the alternator needs to see this resistance in order to turn on. I'm going to say that with the external voltage regulator you might not see 12 volts on the blue wire with the key off, but you should with the key on. It is the field charging wire.

Make sure the alternator body is grounded to the engine block and the battery negative and also to the voltage regulator body.

here is how the external regulator and alternator is wired.

[sKnNyPpY]

Convert to the internally regulated alternator and Mystery Charging Problems suddenly disappear. Re-do the grounds while you're at it, cheap (or free) and everything will get the charge it needs and won't suddenly decide to not work.

[chevy_mike]

As VetteVet showed, my problem was the resistance wire at the ignition switch. It looked fine from the outside but we bumped it and it came apart, finding the internal wire had broken. We fixed that and all the charging problems went away. Again, from just looking at the wires, everything looked okay.

[cdowns]

but that lookin works great with xray vision

[70-K5]

Originally Posted by truckdude239

if i was you i'd swap over to this style alt its the same price as the r old style and more dependable

http://67-72chevytrucks.com/vboard/s...d.php?t=119379

I disagree with the instructions offered in this link. I haven't had to work on my 70's electrical system but wired an 86 K5 electrical system from scratch.

The description of the terminals on the SI alternator are wrong, plain and simple.
The brown wire, (I) terminal, is for the gauge or idiot light, that is all. The sense terminal (S) is what tells the alternator to do. Because the instructions in the link instruct you to connect it to the positive output of the alternator the alternator will produce 14.2v at the alternator output. This is fine but with the resistance and voltage drop throughout the system you'll be running at a lower voltage throughout your electrical system. This is the description of the "one wire" bonehead conversion.

If you're going to alter your electrical system I'd suggest reading up some tech articles at www.madelectrical.com .

[truckdude239]

you may disagree but hey hunreds have done it that way i ran my that way for about 5-6 years before i went though the ls swap

[MARKDTN]

Originally Posted by 70-K5

I disagree with the instructions offered in this link. I haven't had to work on my 70's electrical system but wired an 86 K5 electrical system from scratch.

The description of the terminals on the SI alternator are wrong, plain and simple.
The brown wire, (I) terminal, is for the gauge or idiot light, that is all. The sense terminal (S) is what tells the alternator to do. Because the instructions in the link instruct you to connect it to the positive output of the alternator the alternator will produce 14.2v at the alternator output. This is fine but with the resistance and voltage drop throughout the system you'll be running at a lower voltage throughout your electrical system. This is the description of the "one wire" bonehead conversion.

If you're going to alter your electrical system I'd suggest reading up some tech articles at www.madelectrical.com .

GM wired a bunch of vehicles with the #2 straight to the output post. I know my '86 Cutlass was that way and pretty sure wifes '84 Regal was too. Those would be 12Si instead of 10SI but still the same wiring.

[doodah man]

OK, I got it charging (I think*) by putting in a new alternator. I haven't had the chance to take in the old one to get tested again. I'm wondering if I had the alternator and regulator go at the same time. Or the first "new" alternator I installed in Chatham (see long story) was bad out of the box. I disconnected and reconnected so many wires and plugs that it could have been just a bad connection that I fixed by accident. I'll post the alternator test results when I get them this weekend.

*One more question: What voltage should I see at the battery with everything working? I'm getting 13.6 V with the new alternator engine running at idle. The battery voltage was about 12.3 V with the engine off.

Thanks for all the advice.

[doodah man]

Also, what's the proper way to full field these externally regulated alternators?

[truckdude239]

if your getting 13.6 its charging the older system dont charge very well

[truckdude239]

also you dont have to fuill field these like the old generators

[Bigdav160]

I'm pretty sure you had it correct in a previous post.

Supplying 12v to the field terminal (F) on the alternator should produce full output.

edit:

*One more question: What voltage should I see at the battery with everything working? I'm getting 13.6 V with the new alternator engine running at idle. The battery voltage was about 12.3 V with the engine off.

This tells me the alternator is working. Your battery still has a very low state of charge. Without a inductive ammeter or oscilloscope it's hard to tell if the alternator will produce full rated output.

[doodah man]

Originally Posted by Bigdav160

I'm pretty sure you had it correct in a previous post.

Supplying 12v to the field terminal (F) on the alternator should produce full output.

That's what I figured. I tried it two different ways. Jumped straight from the + battery wire to the F terminal and from the brown wire (4 pin) on the regulator plug. Both were supplying battery voltage.

[doodah man]

Now to get that ammeter working. Is there a FAQ on that?

[Ol Blue K20]

Check the fuses in the corner of the radiator support (drivers side) looks like a little football (fuse inside) the other is over by the junction block on the pass fender (looks like the other one. If I remember correct they are 4 amp fuses