Continued issues with 1968 Olds 442 Charging system,

Maintenance/Repairs
21

OK. When I started it this morning, at high idle (cold engine) the voltage across the battery terminals read 31.41V. Engine off, battery reads 12.3.

I put the (+) probe of my multimeter on the BAT terminal of the alternator, the (-) probe on the positive battery terminal. The meter would often read erratically, as if the voltage was not stable, but it was common for it to read appx 1.56 - 1.59.

The GEN light was OFF under this idle speed.

Now, when the engine warmed, and the idle dropped to normal speed, the GEN light came on.

Battery still read 13.7 with engine running. The BAT terminal on alternator to (+) battery terminal reading was still a bit erratic, but it was more common for it to stabilize around 1.1 V.

Here’s the interesting thing…with the lights on, I can see when the ALT output is strong enough to cause the GEN light to go off, because the headlights brighten. Under these conditions, I pushed on the wiring plug going into the voltage regulator, and I could see the headlights brighten and dim, particularly with the top wire, which I think is the main current input. At one point, the headlights remained bright and the GEN light shut off. Unfortunately, I didn’t re-take the measurement between the alternator and battery before shutting off the engine (stupid). I then re-started the car and couldn’t reproduce the condition where the GEN light is off and the headlights are bright (at slow idle).

So, next thing I am going to do is to work with the wiring connected to the V regulator to make sure they are functioning. I can still see the headlights brighten a bit when playing with the top wire, but I can’t get the unit to work as it should by just tinkering.

I’ll post more information as it becomes available.

Any thoughts on these observations would be helpful.

Thanks so much.

Cryoman

Just FYI - 6.6L 400 CI engine. The 455’s weren’t available in 1968 except in the Hurst Olds configuration (and apparently if one knew how to work the system when ordering).

Best wishes.

22

No way you could read 31.41V across the battery. Do you mean 13.41?

1.5 volts across that cable is quite high, indicating possibly a bad connection or corroded cable. It should read <0.5 volts. But I can’t rule out the possibility of the manufacturer using a thinner cable to save money.

“pushed on the wiring plug going into the voltage regulator” this indicates a problem with that connector, which is in line with the above 1.5 volt reading. What do the contacts look like in that connector? I’d also look for a damaged wire.

23

According to your testing you’re losing 1.5 volts between the alternator and the battery. I think you’ve found the general area of your problem. I would now find a wiring diagram and test that circuit more.

24

You stated that you got over a 31 volt reading across the battery with the engine running. If that is really true then that most likely means something inside the alternator is having trouble. When charging voltage exceeds more than 15.5 volts for a period of time the battery can be damaged. You also seem to have found a problem with the main output lead to the battery. You stated you saw around a 1.5 volt drop across that connection. Which helps explain why your battery voltage is not as high as it should be. Your battery is not getting the full output voltage from the alternator. This kind of test is basically like reading the voltage across the two ends of a wire. Since a wire should have very little resistance that means very little voltage should be dropped across that wire when current passes through it. But in your case you are seeing over a volt of drop on the charging lead. It should be no more than around .3 volts with a high current load on the charging system. I suggest you find out where the fuse is for the alternator output connection to the battery and check for a dirty connection there. Also make sure the battery connections are clean. You have a faulty connection somewhere.

It may help you understand better if you measure the voltage across the alternator output lead and the case of the alternator. That will be the full output voltage. Then measure the voltage across the battery posts. The difference in voltage between those two points will be the voltage loss you measured across the charging lead to the battery (if there are no significant ground return losses).

The number 1 you saw on the meter display is usually an indication that the voltage you are trying to measure is too high for the voltage scale you selected on the meter. You need to move to a higher voltage scale for the meter to take the reading correctly.

25

My typo. 13.41V. I retrieved my best multimeter from the basement this morning and the “1” reading is no longer coming up. It is a Fluke 113 True RMS multimeter. It has an automatic adjustment.

I’ll keep working on the wiring issues you’ve helped me ID. I’ll likely start putting new wiring in where it seems necessary.

Thanks again. I’ll post more when I have something new to write.

Cryoman

26

Use your meter to check suspected bad connection points. I would start at the alternator side then move the meter leads across suspected bad connection points moving towards the battery, even check across a wire end to end to make sure the drop isn’t there. Your meter will tell you where the bad connection is. Fluke saves the day again. A fine choice in meters you have there.

27

31.41 VDC ???!!!

THAT IS NOT GOOD…you have a faulty new Voltage Regulator…and possibly a damaged battery now… Hopefully the batt survived that beating of more than 2X its normal voltage

That Voltage Regulator is wonky… You should NEVER EVER see voltage anywhere near the 30’s

MAX you might see is about 14.5 ish ? Any higher and I would begin worrying about it… But the 30’s…Hell No.

Blackbird.

28

@“Honda Blackbird”

“My typo. 13.41V.” :wink:

29

OH…WHEW…Trust me… it can go that high. Wreaks all sorts of mayhem too…

Damnit I thought we found the smoking gun

Blackbird

30

@“Honda Blackbird”

I’ve not yet encountered a car with that high of a charging voltage

But I remember a few vehicles that had 18V

One of them, the engine started fine, but there were all sorts of weird electrical problems. Several modules weren’t doing anything at all. Lots of idiot lights on, loss of communication, etc.

When I saw the charging voltage was 18V, I recommended a voltage regulator. The customer went for it, and ALL the problems were instantly resolved

Another time, one of the parts guys asked me to check out his car, because there was a strange smell. That strange smell was the battery cooking, because of 18V charging voltage

31

I just repaired a Millionare friends Caddilac Allante… No one could figure it out… Which is surprising since it took me about 2.5 minutes.

At idle his Brand new alternator was pumping out 28.8 VDC…at a few thou rpm’s it peaked in the 40’s

Trust me…that 87’ Computer controlled vehicle did NOT like this… All sorts of insane stuff going on inside the car. Why it didnt fry out is beyond me… At any rate…I declared the brand new and never suspected Alternator as the culprit… He didn’t believe me till I showed him my volt meter.

New Alternator again…and 14.4 VDC at idle… Problem solved…Saved the day. Guy couldn’t believe it

Blackbird

32

@“Honda Blackbird”

Your friend’s Allante . . . 1987 was one of the first model years, if not THE first model year . . . ?

The Allante’s VIN . . . does it reflect that it was built in Italy (the body) or does it reflect that it was built in the USA, where the drivetrain was dropped in ?

Can I presume the " Brand new alternator was pumping out 28.8 VDC" was in fact a remanned alternator and not a brand new part?

Even if it was an AC Delco remanned part, that doesn’t gurarantee success. I’ve seen a few bad factory remans, right out of the box, and I’m sure you have also :frowning:

33

If you read 28 volts, then the current into the battery must be huge. That voltage is the internal battery voltage (12.6) plus the IR drop in the internal resistance. If normal is about 14.5, then you have 16/2 (=8) times higher than normal. Don’t see how the alternator could put out that much current.

Of course batteries are not that simple, so there could be other effects I don’t know about. But it certainly can’t be good for the battery.

34

It’s a good idea for the sake of doing a complete test to do the same voltage drop measurement you did, but on the negative side. So measure the voltage drop between the alternator ground and the battery ground under the same conditions. My guess the above posts are right, the problem is just you have too much resistance between the alternator and the battery for some reason.

35

A good tech armed with his trusty meter can make any electrical nightmare just vanish away.

36

Did the odor from the battery clue you in @Blackbird? Voltage that high seems as potentially damaging as reversed polarity.

37

@“Honda Blackbird” , maybe that alternator was mislabeled, it sounds like it was meant for a commercial truck with a 24v system.

38

I don’t believe there are any 24v alternators that could be mistaken for 12v @keith. The 24v models are all larger than automotive 12v units.

39

Maybe it had a 24v regulator inside instead of a 12v. I don’t know if they can be swapped or not.

40

Sounds like the problem is a loose connector at the voltage regulator. Checking the field voltage at the alternator would lead to the problem but it doesn’t seem like that is going to happen. I would remove each wire connector from the voltage regulator insulator, clean and tighten the connector then reinstall.

The voltage output of an alternator can exceed 20 volts if the alternators 12 volt output cable is disconnected from the battery but in this case 31 volts is clearly a misprint.