Voltage Gauge Pegged

ykf7b0 · Apr 18, 2016

I was driving my 69 roadrunner this morning and I noticed my aftermarket voltage gauge was spiking all the way over at 18 volts. I then headed home but didn't make it. All power was lost after overcharging. I have a Powermaster 7419 externally regulated alternator and and my system has been converted to an electronic regulator. The in dash factory altmeter has been bypassed and wiring upgraded. Bulkhead connector was eliminated with straight through wire. This charging system has been working flawlessly for the past two years. Where do you recommend I start to locate the cause of my voltage spike? regulator, alternator , battery, ballast resistor, or faulty wiring? Thanks!

furryfrog · Apr 19, 2016

I would suspect the regulator, or possibly,since it is an external regulator,the wiring between it and your alternator. If your battery is not cooked from overcharging it and you can bring it back ,I would check it out and load test it if you can, sometimes if a cell suddenly goes, the charging system will try to charge it, hence the over voltage.
Most likely the regulator is faulty and applying to much voltage to your rotor field coils, or a short in the wiring is.

Garys1969RR · Apr 19, 2016

Same thing happened to my 69 RR. Gauge pegged for awhile, then went to slight discharge, and ran the battery down. Poor overworked alternator gave it up. I replaced the alternator and the regulator, now charging system is working great.

65-440 · Apr 19, 2016

I had this sane problem before, new alternator and still overcharched. Did mad electrical upgrade to fix voltage drop in the ignition harness. Still charged high. Replaced voltage regulator, lasted a few months then overcharched again. Turned out to be poor terminal connection at the 2 wire regulator connector. Spliced in a new connector end, no problems since !

ykf7b0 · Apr 19, 2016

I got started tonight on trying to diagnose my problem. I have found my battery to be faulty. I have it removed from the car and when I check the voltage with with my multimeter the voltage increases. I can move the battery just a little and the voltage continues to rise and rise past 16 volts. It is now sitting way back in the yard because it's dangerous. Also, I put another battery on the car and found that I have a dead short immediately after installing the cables. I'm thinking at this point that my hot cable from trunk mounted battery is grounding out. I also believe the culprit causing my problem is some plates inside the battery have made contact sending the power surge through my battery cable and the cable got warm then grounded out somewhere under the car. I will get another chance to look at it in a couple days. Am I on the right track?

miller · Apr 20, 2016

Could be...

BUT, if there's any chance you have a shorted hot cable...another way to say this, I had one, and burned 'every' wire in the car. Lucky the car itself didn't burn!
Find that guy, and fix it, if it's there.

ykf7b0 · Apr 20, 2016

Fortunately for me I have not found any burned wiring (yet). The 60 amp maxi fuse did blow.

miller · Apr 21, 2016

If you have signs of the positive cable grounding/shorting, or any hot wire for that matter, suggest you spend some time looking it over real good.
Doesn't take hardly anything to ground out those cables. How's the routing around the exhaust, or chance it's rubbing on the body somewhere?
Good luck on it!

ykf7b0 · Apr 21, 2016

No hot cable grounding was ever found and the car is running fine. I have a new battery and voltage regulator installed and I'm still over 15 volts. The mad electrical wiring set up is in play. I'm thinking now my Powermaster 75 amp alternator may need to be replaced but I'm not totally convinced it's my problem. What are your thoughts?

65-440 · Apr 21, 2016

Long shot, but have you tried wiggling the voltage regulator connector while somebody watches the gauge ? That's where my problem was

ykf7b0 · Apr 21, 2016

65-440 said:
Long shot, but have you tried wiggling the voltage regulator connector while somebody watches the gauge ? That's where my problem was

I will give it a shot tomorrow night. Thanks!

furyus · Apr 22, 2016

Also, you need really good grounds. If I have this right, weak grounds tell the alternator it's not charging enough, so it starts to put out more power to compensate. Put an ohm meter from the pos battery cable to ground. Will tell you if the cable is grounding .

ykf7b0 · Apr 23, 2016

Update: I have replaced the voltage regulator pig tail with a new one and soldered it in tight and against my better judgement I installed another new alternator but I'm still overcharging at 15 volts and rising. I did notice before I gave it up for the night that my ballast resistor was too hot to touch and my ignition coil was getting hot. Anyone with any suggestions on why I'm still overcharging? It's kicking my butt really good.

65-440 · Apr 23, 2016

Ok, back to basics ... have you checked for voltage drop along the ignition harness ? If not, you might want to take the time to do it. Sounds like you've covered all hard parts that could fail, now you need to check the vehicle for faults. Your alternator might be charging because of the voltage it thinks the battery is at due to false reasons cause by voltage drop at some point or multiple points in that harness.

miller · Apr 24, 2016

ykf7b0 said:
I was driving my 69 roadrunner this morning and I noticed my aftermarket voltage gauge was spiking all the way over at 18 volts.

Just a thought...any chance the connections on that gauge have loosened up? Might be worth checking. Almost sounds like a hot wire grounded somewhere, draining the current...alternator trying to keep up...if that makes any sense.

ykf7b0 · Apr 24, 2016

miller said:
Just a thought...any chance the connections on that gauge have loosened up? Might be worth checking. Almost sounds like a hot wire grounded somewhere, draining the current...alternator trying to keep up...if that makes any sense.

Thanks but since my initial post I have gotten the car running but it's still overcharging (15 volts and climbing over time). I'm thinking at this point the sensing wire is not making good contact somewhere and the voltage regulator is not getting all it needs to tell the alternator to quit producing.

Garys1969RR · Apr 24, 2016

Why not just run a new sensing wire from the battery to the regulator, see if that works. Just put a long alligator clip jumper on there, as a check to see if that drops the alt output voltage?

1968rick · Apr 24, 2016

Check the volage drop to the batt terminal of the regulator...if the drop is too much the regulator is sensing a low batt charge and will try to bring the charge up.

ykf7b0 · Apr 24, 2016

Electronic regulator. Do you mean the blue sensing wire?

Garys1969RR · Apr 24, 2016

I read on another thread that it is the wire that says IGN on the regulator terminal. Pretty sure that's the blue one. It goes to battery positive. Maybe someone can post a simple wiring diagram for the voltage regulator.

Voltage Gauge Pegged

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