Double D Farms

Put a voltmeter on the '69 Cutlass today & had something strange happen. It was doing this before I hooked up the voltmeter, but this confirmed the problem. When the car is idling it will sit at 12 volts for maybe 30 seconds. Then it surges up to about 15.5 volts & any lights that are on get significantly brighter. It stays there a while & then will drop back. It goes back & forth with no apparent rhyme or reason. Also, when the car ignition is off, the volt meter jumps between 10.5 & 12.2 volts. Any ideas?

dmullin

If you have an externally regulated alternator then I would check the connections at the regulator. Give close attention to the regulator ground.

Sugar Bear

Varying voltage is an indication of a intermittent current draw. When the draw occurs the voltage will drop.

Is there any aftermarket equipment on the car, especially anything with a memory? If yes, unplug the aftermarket equipment and see if the problem goes away. If no aftermarket equipment exists unplug the alternator and see if that stops the variation. If not then pull one fuse at a time to see if the problem goes away. Remember to unplug the trunk lamp and under the hood lamp also. Can you tell if the brake lamps are on when this occurs?

Keep us posted...

stellar

It sounds like a pretty heavy draw. You may be able to see hear or smell something when the volts drop. Since the draw is that heavy I doubt if it is on a fused circuit, but that would be the first thing to check. Is there any accessories not working properly? I would also look for spots where wires may be rubbing and worn through or where wires touch hot areas and have burnt.

oldcutlass

It is really not supposed to exceed around 14.5 volts. Sounds like a regulator issue if your meter is accurate.

droldsmorland

My votes the regulator. If thats where your troubleshooting leads you consider replacing the point style with the solid state unit.
Here a simple check:
"Let’s check and find the problem. First, for a stock car, the original alternator should be more than sufficient and have no problem keeping up with the lights and heater fan. First, charge the battery, then disconnect the charger, verify that the voltage on the battery is 13.2 Volts or higher (it should read high due to the surface charge). Now turn the headlights on for 60 seconds. Turn the lights off and check the battery, it should read 12.6 Volts or higher, if not, the battery is weak. Now start the car. Measure the voltage across the battery, if it is not 13.8 Volts or higher, the alternator is not working correctly. If this passes, turn the headlights on. The alternator should be able to maintain 13.5 or higher, even with the lights on and the engine at idle. If the Alternator is not passing these tests, carefully measure the voltage at the rear of the alternator, across the battery terminal and the alternator case with the engine running and the headlights on. If this voltage is within 0.1 Volts of what you were reading at the battery, then either the alternator or regulator is bad. If this voltage reads higher, you have a high resistance path between the alternator and the battery. To find what side is bad (power or ground) begin by measuring the voltage between the alternator case and the battery negative terminal. The voltage should be 0.1 Volts or less, if not, you have a bad ground. Next, check the voltage between the battery post on the alternator and the battery positive terminal. Same as before, if the voltage reading is more than 0.1 Volts, check the wiring between the alternator and the battery. Before you put the Volt meter up, with the engine still running and the headlights on, measure the voltage from the regulator case (use one of the mounting bolts) and the battery negative. Again, the voltage should be 0.1 volts or less. If not, check the ground from the rear of the engine block that connects to the body. Finally, if the alternator failed the test, turn the engine off and attempt to rotate the alternator pulley by turning the fan. You should not be able to rotate the alternator without the engine turning as well, if not, your belt is loose or glazed and this will result in poor alternator output".

This paragraph is complements of Mr Harvey White...tx Harv

stellar

I think it would be unusual for the regulator to be the problem even when the ign is off.I guess anything can happen. I would initially look at #3wire on reg to see if it is grounding out anywhere. Maybe even the alt hot wire. The 2 may be connected somewhere.

Double D Farms

I appreciate all the input guys. Unfortunately paying for the car (work) is taking a disproportionate amount of time right now. Please keep the info coming. I'll check out the fixes that have been given as soon as possible & repost.
Thanks, MIke

Double D Farms

I misspoke when I said "with the ignition off". I meant with the ignition switch on but the car not running. I looked again tonight & heard something under the hood clicking each time the volts jumped or fell while the car was not running. I got under the hood & found the wiper motor was hot. I unplugged all of the wiring to the wiper & washer. Now the car holds a steady 12 volts when the ignition is on but the car is not running. It still overcharges when running. At idle when fully charged it shows over 14 volts. As I rev the engine the volts go up, topping out at about 16 volts. I have not had a chance to check any of the other ideas yet.

1970cs

I assuming that you still have the original type external voltage regulator?
If so you can adjust the rate of charge by bending the tang on cutout side coil!
You must use a good multi-meter set to volts and bend up or down depending on the rate of charge 12.5-13 or so at idle and high of around 14+ with the engine at 2000 rpm or greater.

Some will disagree with this and just replace it due to the risk of burning something up. And the cost is really no that bad around $20 to as high as $65.

Pat

MDchanic

That's your regulator. Replace it. They're cheap.

- Eric

Double D Farms

Yep, $20 for a new voltage regulator. Steady 13.9 volts at idle. Small drop when I turned on the headlights, then right back to 13.9. Thanks for all the help. I'm obviously not an auto electrician!

MDchanic

Glad you got it going! They should all be this easy.

- Eric

oldcutlass

Good job.

pcard

How is your wiper motor?

Double D Farms

Fried!

stellar

I'm suprised you didn't smell it. I'm glad you found it before a meltdown occured. Now on to the wiper motor. There is always something.

pcard

Bummer. Try to get it fixed rather than a reproduction replacement.


Mark (Stellar) may be able to help out.

stellar

It sounds like the wiper motor will probably need to have the armature and fields rewound. Unless this is a show car or you have a lot of money, I would advise against a repair. This is a labor intensive job and will need to be hand wound. It is possible there is an easy fix, but to find out it will need to be taken apart. If originality is not a prime concern I would recomend looking for a replacement motor.

oldcutlass

X2 on a replacement.

Double D Farms

I have a rebuilt one coming in today. I don't recall the manufacturer right now, they rebuild a lot of electrical stuff though. I think it was $68 + I have to send the core back.

Double D Farms

On another note, I had the car running for a while yesterday & put a new multimeter on it. It's not overcharging now but it is still jumping all over the map while idling. I checked at the alternator & the battery. It varied anywhere from 8.9 volts up to 14.5. It just won't settle at one spot. I'm wondering if it may be the alternator?

pcard

The service manual has some pretty good diagnostic procedures you can try on the alternator. I just hope that the surges from your old regulator did not fry some thing else that is now shorting out and drawing down the volts.
14.5 is ok for a charging circuit, 8,9 a bit low, that is why I worry about the shorting somewhere else.

stellar

Are you sure its not just a bad connection of the meter? That is a huge swing. It is worse now than when you had the wiper motor connected.

Double D Farms

Yeah, it's not going as high, but it is still making some wild swings. I'm fixing the brake leak today. Then to the muffler shop. That way, when I get it back I can leave it running a little longer & maybe I will be able to hear something clicking on & off.

droldsmorland

Are all the grounds clean and tight? Are all the positives clean and tight? Are the battery cables and other important wires in good shape on both ends? Pull the alternator and have a reputable starter/alternator/auto, truck electric shop bench test it. You could have a bad winding or failing bridge in the alt. If it tests good Id start pulling fuses one by one to see which circuit is the problem child. You said the wiper motor fried what else fried or melted. What caused the wiper motor to fry etc...thats the circuit I start with for sure. Generally a bad circuit (open or short) will not fluctuate unless its bouncing around due to vehicle movement whereas a bad alternator can exhibit this. Dont rule out the "new" voltage regulator as bad out of the box. In fact you might want to take that to the shop with the alt and have them tested at the same time. A good shop will be capable of this.

dmullin

If you haven't solved your system voltage issue yet, you may want to post where your test leads were when you had a 8.9 volt reading.


Good luck, hopefully you already have it cured.

Double D Farms

I think I finally solved the mystery. I started tracing wires & found a wire that's hot when the key is on just hanging down & as the engine lopes it's randomly hitting the engine block & shorting out. Now the problem is figuring out what it goes to? It's a black wire maybe 16 gauge. It is coming out of the same wiring harness as the wiper motor. I am going to check the schematic & see if I can track it down. Thanks for the help!

Yellowstatue

Black wire goes from wiper switch to wiper motor. What's on your wiper motor plug? A black and a light blue and a dark blue?

droldsmorland

Nothing surprises me with electrical especially after 40+ years worth of hackers & splicers have had their way with it.
Did you ever investigate the solid state voltage regulators? Look the same on the outside but all solid state no moving parts. Ive had one in mine for 6-7 years w/o trouble.