alternator gauge drops and reads low when driving

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Cmbtengineer85

Cmbtengineer85

Darts_for_Troops
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I have a 1973 Dodge Dart that seems to have a wiring issue. I only notice the issue when driving at night because everything on the dash dims down. I will be driving home from work and all of a sudden the alternator gauge will dump down and read on the first or second line. Funny enough there are no performance issues just a surge in my electrical circuit. I thought it may be the alternator so I had it tested and it's putting out around 14.9V at idle. I have had this problem occur when driving and it will run low for usually 10 minutes. Sometimes on the rare occasion it will last longer but I shrug it off because nothing else is going wrong at the time. Recently it has just been either doing the above or it will slowly drop down like the belt isn't tight then if I accelerate it comes right back up without any problems. I never had this issue with my '63 Dart or my '80 Aspen. Though I was the fool who blindly traded an almost finished 63 for a complete start over project. Any idea's on what could be going on?
 
I'll bet you have some damaged wiring between your voltage regulator and the alternator. Check the wiring at the alternator and anywhere on or near the engine. You are probably getting an intermittent connection.
 
Grounds also, and the bulkhead connector if the grounds and wiring seem good.
I would ask the usual ammeter questions, but I'm out of time right now.
 
FOURTEEN POINT NIIIIIIIIEEEEEENNNN??????!??!??!!??!?!?!?!


That is way too HIGH.

Your running voltage, engine warm, should be optimal 13.8--14.2, not below 13.5, nor above 14.5

Start with this:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

You may have one, or a combination of several problems

1.....may have an older "roundback" alternator with limited output, IE 35 A or so

2....The above may not be in good shape, with worn brushes, one bad diode, etc

3....There's always the belt, as in..........slipping

4.....Voltage drop in either the ground, the ignition harness or both, causes OVER voltage. Hundreds of threads on here about that

5....As in the posted MAD article, problems at the bulkhead connector, the ammeter, and ignition switch connector and switch can cause and add to these problems.
 
Ok I'll check these out. Electrical is not my high point on vehicles. I'm more mechanical and body work. Thank you for the info. And 14.9 I may have mis heard the guy that ran the tester on my car. Any possible ways of checking for bad points in wiring besides visually checking them. I do know that a wire can look good and still be bad. And yes the alternator is a round back. Appears to be off of an old 318.
 
I lost you on the description of the problem. The ammeter gage should drop as you drive. It shows current flow in or out of the battery (if factory wiring). After starting, there should be inflow to recharge what was used by the starter. After a short time, it should drop slowly to "0" (middle of gage). You shouldn't see the needle on the left (battery discharging) while driving steady. To verify that your ammeter works, flip the headlights on & off, and you should see the needle jump as the alternator adjusts its output (via voltage regulator).

As far as your stated limitations on electrical knowledge and tools, Harbor Freight has coupons for a free multimeter, and wikipedia and youtube have much info and tutorials on basic electricity and how to use a multimeter. The charging circuit for our cars is very simple and there is much info about common problems and fixes on this forum if you search.
 
If you didn't have it tested at 14.9 volts,, then I will repost what I deleted,,

Loose or worn thin fan belt, slipping under load,, replace and/or adjust as nec.... prob happens worse on rainy days..?

Tighten the belt, and try it,..

hope it helps
 
Mine acted something like yours, when I checked regulator it had the old points style in it, so I changed it for the solid state job and problem was solved. Hope yours is that simple.
 
Check your wiring behind the gauge cluster. I had a problem with a 69 Valiant blowing alternators and regulators every six months. The gauge would jump every once in a while. Turned out to be a melted wire. The main power wire from the alternator to the amp gauge had gotten so hot that it melted the insulation off and was sometimes grounding against the metal dash frame. After replacing all of the bad wires and new alt and regulator, I never had to replace them again.
 
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