Over charge in the road runner.

[mmissile]

I was making a show-off pass in the car today, and we noticed that shitty burnt insulation smell. We I had some smoke come from under the hood, and we were only a block away from his shop[idled it back]. Found some wire places/insulation that were hot[temp]. We tested the car at idle, and it was over 15 volts. I disconnected the field wire from the alternator, and drove it home on the battery.

I took the voltage regulator apart, figuring I'd find the contacts welded together..........wrong. Is it possible that the RPM on the burnout caused the alternator to go full-field, even though the voltage regulator didn't fail? I haven't found anything loose or burnt out....just where heat had got the wire insulation hot.


Ideas or opinions?

 

[440roadrunner]

I've written about his so much I'm blue in the face

Generally over--voltage falls into one of several categories

1.....Voltage drop

2......Regulator out of calibration or other VR troubles

3......Problems in the alternator IE causing full field (mostly 70 / later)

4......In rare occasions, the battery can cause this

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The VR MUST be grounded to "same voltage" potential as the battery NEG

The VR MUST get the SAME voltage as the battery POS to the VR IGN terminal

Sounds easy? It's called voltage drop

"How to check."

Turn the key to 'run' engine off. Stab one probe of your voltmeter onto the battery POS post and the other into the VR IGN connection, all wiring connected "normal."

What you are hoping for is a veyr very low reading, the lower the better. More than .3V (3/10 of one volt) means you have voltage drop to the VR

The circuit "path" is battery---start relay stud......fuse link.......through the bulkhead (red)........to the ammeter.......through the ammeter..........(black)........to the welded splice..........off to the ignition switch connector.........through the switch.........out the ignition switch connector....... (blue "run" IGN 1).........back through the bulkhead.........to the VR and ignition.

ANY loose / bad connections in that circuit path will cause this

=======================

GROUND. VR MUST be grounded MUST. Run the engine at "low cruise" engine warm, fast idle, and check this first with all loads off, and again with lights, heater, etc powered on.

Stab one meter probe into the battery NEG post. Stab the other into the VR mounting flange. Here again, you are hoping for a very low reading, and zero is perfect

Anything more than say, .1--.2V means you need to improve grounding.

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HOW THIS WORKS

The VR IGN terminal is the "sense" terminal. Whatever voltage is DROPPED from the battery, the VR tries to bring the system voltage up to it's calibration voltage AT THE SENSE terminal. That is, it tries to bring the voltage up to say, 14.2. So the IGN terminal of the VR may very well be RUNNING at 14.2----and you can check that, running.

But because there is VOLTAGE DROP in the circuit path I described above, this means that in order for that VR IGN terminal to be at 14.2, the voltage at the battery is 14.2 PLUS the amount of the voltage drop

When I first aquired my Dart there was 1.5V drop!!!! So with the VR trying to maintain a decent 13.8, this meant the battery actually saw 15.4 !!!

 

[mmissile]

Thanks. Electrical is my Achilles-heel. This is the worst case scenario for me.

 

[440roadrunner]

I can step you through this. Post back here if you get stumped. In some ways it's easier than it sounds. One way to fix voltage drop say, in the ignition switch / connector is to simply remove the load on the switch by using it to key a relay, fused off the starter relay battery stud.

 

[mmissile]

Thanks again.

 

[1967gtx]

When doing these cars a common error is the grounding with new paint especially. I always clean the holes, remove a little paint from mounting surfaces and apply some di-electric grease and the same for the connectors/nuts/bolts/bulbs. it's a pain in the a$$ but has saved the day many times over...

 

[mmissile]

That's what I was doing today. I gotta make sure everything is grounding properly. Proper or not, I may run some additional ground straps to vital things. Since the car has been a showcar more than anything, and now I've put a thousand miles on it...I notice some things "settling-in". The left exhaust got a little loose, the speedo cable will need replacing, and the right vent cable must have come off the vent door pivot/crank.

 

[bkleenfltx]

mmissle ......did Gas Monkey build that car??? :icon_lol:

 

[mmissile]

Okay. Alternator checked at 55amps, new ballast, new electronic voltage regulator and ground strap, new ignition switch, replaced burned/hot wire[run2 on switch and out to ballast], cleaned bulkhead connectors, replace positive battery cable end. It has a gell-cell in it, and is 13.24 volts sitting/not running[???]. When reving the engine up to about 3K....about 14.6 volts at the battery. WTF?

 

[440roadrunner]

and is 13.24 volts sitting/not running[???]. When reving the engine up to about 3K....about 14.6 volts at the battery. WTF?

OK you need to be more specific, I'm sure you know what you mean, but I/ we may not

You are saying?

You measured voltage at the VR or field wire with key on / engine off and it's 13.24? But what is the battery voltage?

What you need to determine is, "What is the drop" (difference) between the VR IGN terminal and the battery terminal.

Re-read my post earlier if you will

Also if the wiring is modified, you might post the "path" from the battery, to up front, to the key, and to the VR.

You probably don't want to hear this, but just beause you replaced the switch does not mean you eliminated the problem, IF that's where it was in the beginning.

Your running voltage is NOT that far off, still a bit high especially for AGM

 

[mmissile]

Okay. Today we did the voltage reading at the VR, and it was 1.4
Went under the dash, and found one of the amp-gauge posts was loose. The wire was tight, but the post wiggled. We by-passed the gauge, and the battery was at 12.8[not running]which was almost a 1/2 volt drop. We ran the VR reading again, and it was at .33, again better. When revving the engine to 5K, it peaked at 14.5 and didn't go any higher. It idles at 12.8-13.2 volts. I'm assuming we found the biggest issue. Thanks for the insight and tips. I'm gonna add some more grounds, and keep checking everything else.


Mike/MMissile

 

[440roadrunner]

Somehow I missed.........what alternator / VR you using, that is what year is the car?

Once you get the voltage drop issue fixed, if the charge voltage is still a bit high, it might be a bad connection right at the VR (70, the connector) and it might just be a VR "a little off."

If the total drop all the way from the battery post to the VR is .33 that is not bad, at all.

Be sure to check the ground path as well. All the way from batt NEG post all the way to the VR mounting flange. Check that running, with and without heavy loads fired up.

What you have now, seems to me to be "livable" on the high end.

"Going low" at low RPM is usually

belt pulley size, IE big alt pulley runs slow

Check V drop from alternator to battery

Older alternator or borderline too small capacity, or even something wrong, IE bad diode

 

[mmissile]

It's a 68...single field alternator, with a mopar electronic conversion. I've had one point style and 2 electronic[stock appearing] VR's on it. The current/old-style alternator checked at 55amps. The battery is grounded to the engine, and the VR is grounded to the engine. That seems pretty direct, to me. ??

We also took all the seats out. First we're fat, and it was easier to get under the dash.
.... and second...I'm an idiot and locked the keys in the trunk.

 

[440roadrunner]

LOL. Been THERE. You may be about "as close as you will get." Also VR are temp sensitive, they will change voltage with temperature. There's a chart in the shop manuals, but of course that only applied to OEM VR

 

[mmissile]

Thanks again. I'm keeping components on hand.

 

[HT413]

A couple of years ago I had a similar issue. I posted a how-to thread on the fix that worked for me. My issue turned out to be several oxidized connections between ignition switch, bulkhead and VR. I can't remember the voltage drop I was having, but with each connection I cleaned, the over charge voltage came down bit by bit. I then replaced my cheap voltage gauge with an autometer and realized it was reading about 0.2 high, which brought me down to 14.7 or there abouts.

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http://www.forbbodiesonly.com/moparforum/showthread.php?56124-How-I-fixed-my-overcharging-issues