71 Dart.

temp gauge, fuel gauge, and Ammeter have stopped working.
as per the 71 service manual, I tested the voltage limiter with a test lamp on the back prongs of the gauges. The test light pulsed as it should. So voltage limiter is working.

The other option in the service manual is vague and says to check for faulty wiring or a bad ground from the battery. Can you help me understand what to check next please?

I went to the alternator. it has 3 terminals. one of the field terminals (green wire to the voltage regulator) is loose and won't tighten up. Will this affect the gauges?

all light bulbs and turn signals are working. the 3 gauges do nothing.

thanks so much. God Bless

Keni

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isaiah6:8
www.kenithomas.com

From your description, I think you have multiple electrical issues, so first try something simple.

Unplug the bulkhead connector on the firewall and check for corrosion or signs of overheating; if you see much, clean it and plug it solidly in again - corrosion there can cause lots of intermittent problems. Pull & clean all the fuses; same issue; doing that cleared up mysterious problems in my '71.

If that doesn't work, you'd really benefit from having the Factory Service Manual (FSM) schematics - they're worth it. The layout of the electrical system in a '71 is fairly simple, but those schematics with color codes are well worth the money!

On my '71 Satellite (I can't tell on from these simple schematics if the Dart has 1 or 2) there are 2 flat connectors under the steering column; one for the turn signals/hazard flasher and another for the ignition switch. Unplug and inspect them too - I've helped another '71 owner where he lost IGN power but had everything else because 1 pin there had gotten hot and melted the housing allowing the pin to fall out of contact.

The ammeter doesn't use the voltage limiter, so start there. I only have simple schematics in front of me, not the FSM, so I may not have all the colors /pins right. I suggest you use a good 12V test light - a digital multimeter may not draw enough current for a good test. Be sure to test that you've got a good ground for the test light at each step.

Test your light at the battery (+) post, then the post on the starter relay. There's a large-ish wire running from the starter relay to a fusible link (usually a thicker flexible wire with a molded in rubber flag) and the link goes into pin J on the bulkhead connector. It ought to have good solid 12V all the time from the battery at the pin on the engine side. The mating pin under the dash ought to also gave good solid 12V. A heavy red wire runs from that pin up to the ammeter stud - it ought to also have good solid 12V. The other stud ought to have the same and have a black wire. That wire runs back to the bulkhead pin P

On the other side of pin P, a heavy black wire runs to the big BAT connection on the alternator (via a connector) - you ought to see 12V there too.

All the power for the rest of the car (excluding the starter & relay) is from a splice on the black wire under the dash running from the ammeter to pin P.

If that's good, turn on your headlights and see if the ammeter moves and the headlights light up. If the lights work and the ammeter doesn't, it may have corroded in place - there's not much to go wrong with it.. If you don't have headlights, you need to check the headlight connector switch and if not there, go back to the splice. If your headlights work OK, you're ammeter may not be reading, but it's not preventing anything else from working.

If things aren't clear at this point, you may have a high-resistance connection. Repeat the tests with the headlights or hazard flashers ON and look for a dim test light. Don't overlook the possibility that the ignition switch is worn and making a poor connections too - especially if things sometimes work.

The pulsing at the voltage limiter tells you that it's working - connect the test light to the sensor lead and the guage ought to read ~1/2 scale and the light flash somewhat dimmer.

If you trace the problem to splices or breaks within the harness, I strongly suggest you remove the harness from the car before you attempt to fix it. It is usually not too hard to repair harnesses unless they've been totally fried, but a FSM is your best investment. Replacement harnesses can be had for a reasonable price, but I've never needed one.

Also, the nuts on the ammeter studs tend to get welded in place; forcing them breaks the ammeter. If the dont' come off easily, I cut the wires as close to the ammeter as possible, then use Dremel #409 wheel to cut the nuts off the stud and carefully crimp new lugs on the wires..

I've found that working under the dash is very painful, so I often remove the seat to get more space.

Good Luck!

"I've found that working under the dash is very painful, "

no doubt. thank you for taking some time and giving me a thorough answer. I will start tonight on backtracking from the battery and checking to see where Im loosing my 12v to the ammeter.

_________________
isaiah6:8
www.kenithomas.com

If I can add another tip here: When you find what the problem is, and you still want to keep your ammeter, do what I did on my '72 Satellite. Drill out the bulkhead and fuse box where the black wire from the alternator goes to the ammeter, and drill out where the red wire comes from the ammeter. Run the wires through the holes, eliminating the spade connectors, a source of corrosion and resistance. Chrysler did just this with police/fleet vehicles in that era. Just something to think about. Make sure you solder the wires, don't use butt connecters. Its a pain, but worth it. Also, when you put the bulkhead connecter back, pack it with grease. It seals out moisture and oxygen, preventing corrosion on the connecters. Yeah, under dash work is a real joy....