Jumpy volt gauge

-
valiant1966

valiant1966

Well-Known Member
Joined
Oct 3, 2009
Messages
330
Reaction score
10
Location
Fairfield,Ohio
My volt gauge seems to jump around a lot. 12 to 14 or so. All to the charging side but still jumpy.
I have new alternator, new regulator, new gauge, new belt and all new connections. Yep! It's a new build. Anyway, what are the possible causes of this or is it normal.
Oh yeah, battery, not so new but holds a charge, etc. Thanks as usual for any help. Dennis
 
Is this just at an idle? I had one on my 77 W200, did the same thing. Going down the road , it smoothed out. I don't think the engine turns enough rpms at idle to "excite" the alternator. Someone smarter than me can give you a better explanation.
 
New doesn't mean a whole heck of a lot today. Could very well be a bad regulator.
Could be a poor ground connection(s) too.
The regulator must be grounded at it mounting. The ground wires to engine and chassis must be clean and tight.
 
Is this just at an idle? I had one on my 77 W200, did the same thing. Going down the road , it smoothed out. I don't think the engine turns enough rpms at idle to "excite" the alternator. Someone smarter than me can give you a better explanation.
Click to expand...
Actually, I hadn't noticed whether this is only at idle. That IS when I looked down and noticed that it was jumping around a lot. I'll check it at cruising speeds tomorrow. Thank you.

New doesn't mean a whole heck of a lot today. Could very well be a bad regulator.
Could be a poor ground connection(s) too.
The regulator must be grounded at it mounting. The ground wires to engine and chassis must be clean and tight.
Click to expand...
I know new doesn't hold much water now-a-days(this is alt #2, first was bad) but was kinda checking on here for other possibilities. As for connections, that is why I stated all new connections(with new wire and connector ends with bare metal points of contact. Thank you.
 
On a possibly related note, is this the correct style voltage regulator to use with my Mopar electronic ignition? thanks, Dennis
regulator_zps0d75acd7.jpg
 
Constant flow Mopar "Racing" regulator. My headlites would dim when the idle dropped. Somebody recommended this regulator (P3690732), which I got directly from Mopar dealer ($23). I installed it on my 69 340 Dart and it has kept the headlites bright even at idle. Havent had any problems but there are some threads on here regarding this item... heres one of many:

http://www.forabodiesonly.com/mopar/showthread.php?t=167911&highlight=racing+regulator
 
Check your bulk head connection for the 2 main power wires going through the fire wall. One is red the other is black, they go to your ammeter in the dash and supply power for everything under the dash. Under the hood the red wire comes from your starter relay and the black comes from the alternator, they both go to the bulk head connector. I just went through this problem with my 70 Dart. Turned out my black wire was very corroded on the interior side of the bulk head connector. I eliminated the bulk head connection for the red and black power wires, crimped, soldered and insulated the connection. My voltage is steady as a rock now! My car starts and runs better! Check out the website "madelectrical.com" he does a good job of showing you how to fix it. Remember this was on my 70 Dart, I'm not sure if your car is exactly the same. You should have the electronic voltage regulator, you have the pre 1970 style in the picture.
 
This problem can have a number of causes

1--Bad regulator, usually caused by the old mechanical relay type

2--Voltage drop in the harness, something I continually preach "around here." This is the circuit path "in a stocker" from battery -- fuse link -- bulkhead connector -- ammeter -- ignition switch connector -- through the switch -- back out the switch connector -- back out the bulkhead -- to the regulator IGN terminal

3--Ground loop or other ground problems. The VR MUST have the SAME connection as the battery negative terminal. PERIOD.

4--Modern problems. It is possible in some cases that some elecrical interferance from systems can affect other systems, IE high output ignition systems can generate interferance into the regulator.

There is also a wierd problem that can only be described as a kind of oscillation or feedback loop. I've seen this a couple of times, and didn't understand until the second time around. What CAN happen is that some alternators can "accidently" or by poor design have a poor cut--in characteristic. The engine slows down a little, the regulator says, "Hell, we ain't chargin" and ramps the field current way up. The engine speeds up a little, and suddently the alternator bangs in there and the voltage shoots way up, and the regulator drops back TOO FAR, then has trouble deciding how to compensate.

The only two times I "saw" this, seemed to be a combo of "try a different regulator" and a different alternator.

(I'm non an engineer, not paid to be, nor do I play one on TV)

5--"Easy stuff" like slipping fan belts. Take nothing for granted.
 
I have the same problem with my car and I have changed out the regulator a couple of times I think it stays good for a while than it starts the bouncing back and forth. This last weekend I took apart the bulk head connectors and cleaned them ran a seperate ground wire from the regulator to the battery and also checked voltage at the back of the alternator with a digital meter and it show's it bouncing. Also checked wires that run through the ignition switch and found that the ignition switch was loose and tightend it but it still bounces. I had a few issues before with the wires not being on the right post's with the blue and green wire at the alternator; would this ruin a regulator? I have have done all the upgrades that MadElectical suggested, it still charges just bounces back and forth like others have stated before it drives you crazy. I'm sure i have the wires run right now between the blue and green wire on the alternator so I will go ahead and change the regulator again to see if it will stop the bouncing. I have also tried a new alternator and it does the same thing. do you guys know of anything else to try?
Pat Faley
67 Notchback
East Peoria IL
 
1--Have you read some of my posts in reference to voltage drop in the ignition harness?

2--Does not matter which field wire goes to which alternator field connection

3--Did you do the MAD bypass as they suggest? I would at least temporarily for troubleshooting run a heavy about no6 wire directly from the alternator output post to the starter relay battery stud. If you don't have no6, use about 3 no 12's in parallel, or 4 or 5 no 14's in parallel

4--How did you check the regulator for ground exactly?

5--Last and "should have been first" what do you call "bouncing?" Are you watching a voltmeter or an ammeter, and where is it hooked up exactly?
 
I did all of the upgrades suggested by MAD and also ran 10 gauge from the alternator to the starter relay and ran a power stud that I bought from mad to power various devises in the car; relays for the headlights and, relays for a sixteen inch fan, stereo and amp. I ran my power for the volt gauge from the fuse box and grounded it to the frame of the dash it is hooked together on a gauge set Volt, temp, oil. I ran a seperate wire from the negative side of the battery to the case of the regulator. When I checked the voltage with the meter at the alternator stud it showed the voltage going up and down from 13.8 to 14.1 and sometimes staying steady around 14.1 for a view seconds just like it shows on the gauge. It is a sun gauge set and like i said I tried changing the alternator and i have three extra regulators that i tried and they all do the same thing. I did do the upgrade to the newer stlye regulator per the wiring diagram from various mopar sites. Yes I have read alot of your postings and that is why i have been looking into all this. I'm not a wiz kid when it comes to understanding electrical stuff but I can read a simple wiring diagram don't understand them but just enough to probably get myself into trouble.
 

I'm not sure I'd consider 13.8--14.1 much of a problem. You have a radio? Any whine in the radio?
 
At one time I remember hearing a whine in my radio but haven't done any long trips with the radio on to notice if I still have the whine. Thanks for all your help so you don't think that is a problem i should be worring about like i said before it is charging just doesn't stay steady.
Pat
 
You must log in or register to reply here.
-
Back
Top Bottom