DansYellow66

I posted this on the Mopar B-Body forum but thought I would throw it in here for some thoughts on how to trouble shoot this thing - there are some pretty sharp guys with electrical issues on here I know. It's all alternators, voltage regulators and batterys.

"My 67 GTX hasn't been run in 3 months due to a bad radiator. Finally had it re-cored and installed new water pump. When I finally started it today, the battery spun it over OK. It took 4 primings of the carb and key starts before it filled the carb and kept running so the battery seemed to be doing it's thing.

After I got it running, I engaged the AC and let it idle while I topped off the radiator and sealed everything up. I sat back down inside and noticed the voltage was low - about 10 - 10.5 volts at idle with the AC compressor engaged and fan on high and the dash amp gage was showing discharge. I have voltage and oil pressure gages under the dash. I reved the motor up some but the voltage did not increase hardly any. It typicaly use to run about 14 - 14.5 volts or a little more once above about 1000 rpm falling to maybe 13 at idle with the AC on. I killed it and then re-started it and the starter seemed to turn a little slow so I decided to charge the battery.

I put a battery charger on it for a couple hours (slow charge rate) but although showing close to 100% charge it never did fully charge and go into a float stage. Voltage across the battery posts was about 12.6 V.

I decided to venture down the road in the car and see what it would do. It re-started fine but still had very low voltage. I turned the AC off and the voltage jumped up about 1.5 volts - maybe a little more. Turned the AC back on and the voltage drops back. But even with the AC off the voltage doesn't get back to the 14 - 14.5 volts it ran before. With the AC off the amp gage reads slightly positive but at 50 mph the voltage was only reading about 12.5 to 13. When I got back I killed the motor and it re-started fine.

I've had this car about 10 years and it has the usual rebuilt alternator on it of questionable output. I put a solid state voltage regulator on it when I first bought it and it has seemed to work OK - at least up until now.

How do I best trouble shoot this thing? Electrical is not my strength as beyond knowing enought to not hold a spark plug wire to my tongue - my skills are about tapped out. The shop manual isn't a lot of help as it mostly discusses testing components rather than basic system checks. I'm tempted to put a new rebuilt alternator on it but then I wonder if the voltage regulator has crapped out. And then the high voltage drop when I turn the AC on makes me wonder if the fan motor has about kicked the bucket and is pulling high amps. The battery could be an issue but it seems to be holding up. I'm leaving it on a charger tonight.

I have a decent multigage electrical tester and a few other things like a test light, so I can do some basic checks if anyone has any suggestions. I've read the trick of pulling the positive battery cable with the motor running is not a reliable test of the charging circuit and doesn't help pin-point the problem. I may still have the old mech voltage regulator also that I could re-install, but I will have to look for it.

Another note - I have a green **** battery disconnect on the car and I have problems with it not making a good connection but I assumed that would only cause a starting problem when amp draw was high.

Thanks in advance for any help. "


Dan

5thvet

Here's a pretty good troubleshooting guide from Plasticman.

http://api.viglink.com/api/click?for...13441309438431

GUSTO14

Dan, I'm not a MOPAR person, so I may not be any help in trouble shooting a MOPAR alternator, but the first thing I would do is get a good digital voltmeter and test the battery voltage with the engine not running. Then I would start the car and recheck battery voltage. If nothing else this will confirm that it isn't your voltmeter gauge that is off. Obviously it should be reading somewhat higher. As you previously indicated somewhere around 14 volts is normal.

If the voltage reads the same as your gauge does, the next thing I would do is connect the digital voltmeter (red lead) to the "12v" terminal of the alternator (black lead to a ground) with the meter set on AC (as opposed to DC). With the engine running, see if you are getting an AC reading of voltage. If you are, it's telling you that a diode in the alternator is shorted and it needs to be replaced. If you're sufficiently talented you can even take it apart and replace the bad diode... or just head on down to NAPA and pick up a "new" alternator.

Good luck... GUSTO

Pilot Dan

Get yourself a new SOLID STATE Voltage regulator (under$20). I'll bet that solves your problem. Pilot Dan

DansYellow66

I got some pretty good info now - much better than the gobbly gook with all the special devices, gages and tools in the Plymouth service manual - checking cell acidity, post adaptors, etc. I'll do some testing today and see what it does. Battery was still charging when I turned in last night which seems to be taking a long time - so now I'm starting to suspect it, although it turns the engine over pretty fair. I checked and it is 7 years old. These old Mopars always sound a little labored starting though. Old Mopars also suffer from the dreaded bulkhead connector syndrone also so there are lots of similarities with our Corvettes in the engine electrical.

Thanks. I'll report back.

Dan

dplotkin

Yup, could be.

Dan, I own two Mopars. Assuming you have clean, tight connections, a healthy battery, and a tight alternator belt, I'd say the prime suspect is an alternator with one or more bad diodes or even more likely worn brushes. A bad solid state regulator would more than likely not charge at all, or possibly overcharge. With the A/C on at idle you might not see 14 volts even with a properly functioning charging system. the clutch coil, fan and reduced engine RPM account for that.

Pull the alternator & bring it to one of the national parts retailers (Advance/AutoZone) and they can test its output in their machine. The battery should be load tested too, but a battery cannot be properly load tested unless it is at full charge, and if it won't take a charge, it is no good anyway.

lastly, unlike our C2's, Mopar electrical systems from this period run all current the car uses & generates through the ampmeter and it gets there through the firewall bulkhead connector, a poor design. Ampmeters and the conductors in the bulkhead connector are known to burn out, especially when the alternator is near or at full output trying to charge a empty battery. Many Mopar owners run a #10 with a fuse from the alternator output lug to the battery. It makes the ampmeter innaccurate, but it avoids melting bulkhead connectors, smoked ampmeters with resultant side of the road experiences.

Good luck.

Dan

DansYellow66

Here is the result of the testing I did this morning.

Here are the results of this testing. I put the voltage readings in parenthasis in the body of your post. The battery was fully charged this morning and it did seem to be more back to normal when I started the car.

Quote:
Originally Posted by Pops1967GTX
Well since its been sittiing for 3 months... First I would check all connection & grounds.. Test Battery...
From my manual testing alternator/regulator....
Battery test...
1. Connect the positive lead of the voltmeter to the positive terminal of the battery and the negative lead to the negative terminal.
NOTE: Protect your eyes with safety glasses or goggles when doing this procedure.
2. Remove the coil cable from the distributor cap.
3. Ground the coil cable to the engine block by connecting a jumper cable between the two. This will prevent dangerous arcing of the high-voltage spark.

NO-LOAD TEST
This test will determine whether or not the system is charging the battery and, if not, whether the alternator or regulator is at fault. It requires a voltmeter capable of measuring at least 16 volts, down to tenths of a volt.
If the charging system on your car has an externally mounted regulator, warm up the engine before performing the following test:
1. Turn off the engine, lights, and all other accessories.
2. Attach an engine tachometer according to the manufacturer’s instructions.
3. Connect the voltmeter to the battery by attaching the positive lead to the positive terminal and the negative lead to the negative terminal.
4. Note the voltmeter reading. (13.1 volts right after taking the charger off of it). If it is less than 12 volts, charge the battery. Then note the voltage reading again and record it.
5. Start the engine and slowly increase the speed to 1,500 rpm.
6. Note the voltmeter reading again. If it exceeds the engine-off voltage by more than 2 volts, the system has a faulty regulator, a poor regulator ground, or a short circuit in the wiring between the alternator and regulator. (On my meter voltage was reading 14.4 to 14.5 volts. Inside the car the gage was 14.3)
7. If this voltage reading exceeds the engine-off voltage by less than 2 volts, perform a load test.
LOAD TEST
1. Keep the tachometer and voltmeter connected as they were for no-load test.
2. Note and record the voltage reading.
3. Start the engine and turn on the heater (or air conditioner) at high speed. Turn on all lights and accessories. (AC and lights on. First try was only about 12.3 V but I was getting belt slipping. I tightened the belts and in eventually climbed to 14.1 volts at around 3000.)
4. Increase the engine speed to 3,000 rpm and note the voltmeter reading.
5. If this reading exceeds the engine-off voltage by 1/2 volt or more, the charging system is functioning properly.
6. If his reading exceeds the engine-off voltage by less than 1/2 volt, perform a full-field test.

FULL-FIELD TEST
When the regulator’s control function is bypassed, the alternator runs full-field. The method of bypassing the regulator differs, depending on the type of vehicle. For this reason, Step 1 of the full-field test changes from car to car, while the remaining steps are the same for all models.
1C. Chrysler models. Turn of the engine. Locate the green wire connecting the alternator field terminal to the regulator; disconnect this wire from the alternator. Connect a jumper wire from the alternator field terminal to a good ground.
2. Once the regulator has been bypassed, repeat the load test.
3. If the full-field voltage exceeds the engine-off voltage by 1/2 volt or more, the regulator is defective and must be replaced...............do not jump the green wire to anything.(Engine off voltage starting was 12.74 volts. Reving the motor brought the voltage to a steady 12.25 volts)

REGULATOR REPAIR
Once it has been determined that the problem is with the regulator and not the alternator, you can find out if the source is the regulator itself or its wiring or ground.
1. Check the wiring between the regulator and alternator for heat damage or wear. The regulator is usually mounted on the firewall or on the finder under the hood.
2. Remove the bolts from the voltage regulator.
3. Use sandpaper to clean off the area around the bolts and the spot where the voltage regulator mounts on the car. This will assure a good ground.
4. Clean, reinstall, and tighten the bolts.
5. Perform all of the troubleshooting procedures again to see if the problem still exists.
6. If so, the problem is either in the wiring or the regulator itself. If you have already inspected the wiring, try replacing the regulator

A couple other notes. Starting voltage was about high 10s to low 11 volts when cranking. I noticed that with accessories off my inside volt gage reads pretty much the same as my meter hooked up to the engine. But, as I engage accessories, the inside voltage is dropping below what the engine side meter is reading - maybe as much as 1-1/2 volts or a little more - especially at lower rpm. I cleaned up my bulkhead connector many years ago - could this be an indication it needs attention again? Or maybe some bad grounds?

It looks like the battery was just low and the charging system is working from this. Still a little surprised by the voltage display on my interior gage as I don't recall it dropping as low as it is before. It usually read around 14 or more volts going down the road.

Thanks for the help

Dan

Anyone have any additional thoughts on this???

Thanks

Pilot Dan

Dan, your original post indicated "I sat back down inside and noticed the voltage was low - about 10 - 10.5 volts at idle with the AC compressor engaged and fan on high and the dash amp gage was showing discharge."

That indicates a no charge condition which will also run the battery down pretty quick. My money is still on the regulator (or possibly the alternator). Test the alternator output and you will have the answer.

DansYellow66

Well - there's nothing like going about things in reverse order and doing basic maintenance last. I pulled all the cables off and bronze brushed the dry powder off of them and uplugged the bulkhead connectors and plugged them back in. Now it acts like it's old (it is old) self - the alternator jumps at the slightest touch of the throttle and the inside voltage is up around 14 volts holding steady. I've been working so hard on this other car I'm building - I need to go back and do some maintenance on my other cars. Much ado about little in the end.

Thanks

5thvet

Love when it turns out simple!