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Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144439
02/04/12 04:08 PM
02/04/12 04:08 PM
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I was trying to get you to use the meter that you checked across the battery with to check the voltage at the point your inside gauge is connected to. As others have said, an analog gauge may react differently than a digital gauge but it would be nice to know.

I would guess your MSD switching is causing the flick, but, nothing like proving it.

And, unless your regulator is bad, I would still suspect your blue wire is reading a lower voltage than you are seeing at the battery with the meter.


Steve
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144440
02/04/12 04:16 PM
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Quote:

""I bet the blue wire at the alternator is .6-.7v lower than the battery voltage, causing the regulator to pump the voltage that much higher. This is caused by the resistance in the connections between the battery and the blue wire (bulkhead, etc).""

I have already had to bypass the blue wire around the bulkhead last year. I will try and trace the blue wire and ispect the connections.

""You can measure this difference, and if you jump the battery + directly to the blue wire at the alternator, you should go back to 14.5ish at the battery.""

Do you mean to "disconnect" the blue wire at the alternator, or add an additional wire from the same alternator blue field wire over to the "+" battery cable and start the engine?
Then measure the voltage again at the battery and at the alternator to see if they match? If they match and if the battery voltage is now lower, then the blue wire connections is the issue?

Thanks for your reply.
It will be a few days before I can get back on this but I will add this to my hit list.




I think I left the blue wire hooked up with a spade terminal splitter thing and started it. With the DMM hooked up I had ~15.5v. I hooked up the jumper and it immediately dropped to 14.5ish, verifying that was my issue. You can also put the negative lead of your DMM on the blue wire, and the positive lead on the battery +. That voltage should ideally be 0v. Whatever voltage you do read will be how much higher the battery charges than it would otherwise.

Also, if you leave the jumper hooked up, it will not turn off with the key

You can also hook up the jumper then start it, but don't let it sit there long without running; it's just like having the key on Run without starting it. In theory the points/coil could burn up.


I ended up installing a relay triggered by the blue wire to provide power directly to the regulator/alternator.


If you ever find yourself in a fair fight, your tactics suck.
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144441
02/04/12 06:42 PM
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Quote:

I am using the stock wiring harness except that at the bulkhead, I had to bypass the blue wire around the bulkhead last year due to a burnt connector. Since the bypass, it ran fine all last year.
This came up on my last thread so I will throw it out there. I just installed a MSD ignition box and on the 12v switched feed to the MSD box, I connected three wires, the RUN blue wire (goes to the alternator/VR), the brown CRANK wire, and I also wired in the voltage guage that is showing a fluctuation of 13.5-14.5. These three wires are what is feeding the MSD 12v feed. I asked a MSD tech about wiring the voltage gauge in on the 12v supply and they said that it would be fine. I am not 100% sure on this as other board members have questioned it too.

Thank you.






You answered your question here. You had to by-pass a burned connection. You fixed one, you probably have atleast one more.

I had the same problem on a 71 Challenger R/T. The ammeter gauge would discharge a little at idle, not much, but when I'd rev the engine or drive, the needle would go way up. I changed voltage regulaters, alternators, added grounds, did who knows what all. Still no solution. I actually cooked the battery one or two times. Litterally blew the caps off of it. Had it to a few shops and no one could find it.

One day I was messing around looking under the dash and noticed a black streak in the steering column to main harness connection. I tried to pull it apart, but couldn't. So I cut the wires and spliced the two together. From that point on, the car charged correctly.

Keep looking for a burned connection somewhere!

Re: Ammeter/Main Voltage Fluctuating [Re: 70HemiGTX] #1144442
02/04/12 07:36 PM
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I am thinking of pulling the front engine harness out of the car and inspecting all of the connections. Then tape it back together after replacing as much of the blue wire that I can find. Then retape it back into a harness again once I am sure that it is in good shape.

I am also going to check the green wire going from the VR to the alternator for any resistance.

Thank you all for your help.


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144443
02/05/12 01:45 PM
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I just pulled the VR connector loose and made a continuity check on the green wire (VR to alt) and it showed .3/.4 ohms.
What does this tell me? Is this too much? If so, I will cut this wire out and splice in a new one.

I am now looking at the blue wire where I bypassed the bulkhead.

Thanks


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144444
02/05/12 01:52 PM
02/05/12 01:52 PM
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Touch your two meter leads together and see what their resistance is (probably .1 or .2). Then deduct that from whatever you measure.

A run as short as the green wire should be dang near 0ohms.

Another good way to test is to measure the voltage drop under load.


If you ever find yourself in a fair fight, your tactics suck.
Re: Ammeter/Main Voltage Fluctuating [Re: hooziewhatsit] #1144445
02/05/12 02:15 PM
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My leads showed 0.0 before I took the above reading.

I reviewed my connections for the MSD 12v source and this is what I had:
Blue Run
Brown Crank
MDS Small Red
Voltage Gauge wire (this is my second inside voltage guage to watch my 12v source to the MSD from inside of the car)
(2) Brown wires from previous ECU setup that showed 12v during Crank and Run.

I just removed the two Brown wires that used to feed the ballast and now I just have the MSD Red, Blue, Brown, and voltage guage at that connection.

I am going to follow my blue wire next.

thanks for the reply.
Should I replace the green VR wire?


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144446
02/05/12 04:18 PM
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I changed a couple of the connectors on the Blue wire/White tracer that goes from the bulkhead to the alternator.
I started up the car and the ammeter and battery voltage are still fluctuating at idle (wild)and at high idle (1200rpms) the ammeter is only in the "+" and my inside voltage gauge shows 14-16v and at 1500rpms the ammeter and voltage reading is solid.

At high idle, I took a voltage reading at the battery and it showed 15.1-15.3 and at the alternator main stud showed 15.2-15.5 volts.
Since they are both showing approximately the same reading (still high), what does this tell me? Is this showing a VR problem?

Does the .1-.2 ohm reading on the Green wire from the VR to the alternator seem like an issue?

Turn signals and Hazzards are acting fine.

thanks again.
Now I am going to start looking behind the dash.


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144447
02/05/12 05:43 PM
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I still say you have a bad connection on one of your "heavy" main power wires. That is what is causing your alternator to work harder. Some where you have a poor connection. Trace all of your heavy red wires under your dash, up the steering column, and out to the starter relay.

Re: Ammeter/Main Voltage Fluctuating [Re: 70HemiGTX] #1144448
02/05/12 05:53 PM
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I now have the dash panel off that has the headlight switch/wiper switch and also the main gauge cluster off and I do not see anything obvious. The ammeter studs are tight and tomorrow I will check the ammeter wire connections. Then I will work around the fuse block, then the steering column connector, then out at the starter relay.

Thanks again.


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144449
02/05/12 06:02 PM
02/05/12 06:02 PM
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jumping across various points may help you find a circuit of high resistance if you hit one that straightens it out. I'm rootin for ya


live every 24 hour block of time like it's your last day on earth
Re: Ammeter/Main Voltage Fluctuating [Re: RapidRobert] #1144450
02/06/12 04:55 PM
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I checked the ammeter wiring and it was tight. I checked all of the wiring for the headlight switch and the wipers and all was good. I pulled both of the connectors on the steering column and they were all clean. I looked under the dash for other issues and did not find anything obvious. I did find a loose connection at the accessory feed that goes to my electric choke and I tighten that up. But I found nothing that showed a loose connection.

I know from yesterday that the green wire at the VR-Alt showed a continuity check of .4ohms.
Today, after I got the dash put back together, I turned the key to the "RUN" to check the voltages at the battery, VR, and at the field wires of the alt:
Bat: 12.1v
VR: Both green and blue showed 11.9v
Both Alt Field wires showed 14.1v!!!!

How in the He99 can I get a reading at the alt field wires that showes a voltage 2v higher than the VR and the battery feed with the engine off????? (Engine off, key at the RUN position)
Do I have an electrical transformer under my hood?

Thanks


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144451
02/06/12 05:02 PM
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Techwest Racing shows a test for MSD ignitions as shown"
"" How to check Your Msd Ignition Box For Damage For the Racer who feels they have a failed MSDŽIgnition, there is a simple test that TechWest Racing Services can walk you through to confirm a true failure of your MSDŽIgnition.

First you will need a Volt/Ohm meter (this check can be performed with an analog or digital meter as well). The type of meter will not change the outcome of the test performed. Set your volt/ohm meter on the 1k ohms scale, then position the MSDŽIgnition in approximately the same orientation as mounted in the vehicle. This is done to ensure that the MSDŽIgnition is relatively in the same position as when the failure occurred. Next take either lead and attach it to a bare metal area on the MSDŽIgnition. The second lead needs to be hooked to the Large Red wire that provides your main 12vdc input. In an Undamaged MSDŽIgnition the needle will stay in the home position (ie. max Ohms for scale chosen). A Damaged MSDŽIgnition will show a reading of 3k ohms or lower.

The readings mentioned above are the result of our experience with repairing customers MSDŽIgnition systems. If you plan on testing your MSDŽIgnition while it is still mounted in your vehicle PLEASE remove the LARGE RED wire (ie. main 12vdc). Failure to do this will result in possibly damaging your meter while performing this test on your MSDŽIgnition.""

What do you think?
Removing the BIG RED wire from the battery and checking continuity in the box? How would this hurt a meter?

Thanks


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144452
02/06/12 06:36 PM
02/06/12 06:36 PM
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Quote:

What do you think?
Removing the BIG RED wire from the battery and checking continuity in the box? How would this hurt a meter?




It sounds like the test is measuring the resistance from the power input to the case ground on the MSD. Ideally there would be no connection. If it measures 3k or lower, there's a connection to ground internally (which apparently is a bad thing).

I'm not quite sure how it could damage the meter, but I would agree it would be best to disconnect the input before doing the test. Otherwise, you're also measuring the resistance to ground of any other device that's also hooked to the battery + terminal.




Quote:

Bat: 12.1v
VR: Both green and blue showed 11.9v
Both Alt Field wires showed 14.1v!!!!
How in the He99 can I get a reading at the alt field wires that showes a voltage 2v higher than the VR and the battery feed with the engine off????? (Engine off, key at the RUN position)
Do I have an electrical transformer under my hood?




What were you measuring when you say the Alt field wires? Those should be the same as the green and blue wires. Otherwise, I have n idea how you measured 14v


If you ever find yourself in a fair fight, your tactics suck.
Re: Ammeter/Main Voltage Fluctuating [Re: hooziewhatsit] #1144453
02/06/12 08:01 PM
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""What were you measuring when you say the Alt field wires?""

Hand held meter: black on ground and the red on each field wire (one at a time) to measure the voltage at the alternator with the key at RUN, VR connected.
I was expecting to see the same voltage that the VR showed but I was confused when I found the 14v reading. I turned off the key and thought about it then I made the same test again and found the same 14v reading.
I don't understand how it can show 14v at the field wires (VR connected)when the blue and green wires at the VR (disconnected from the VR with the key on) gave me 11.9v.

Last edited by YO7_A66; 02/07/12 08:20 AM.

1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144454
02/06/12 11:14 PM
02/06/12 11:14 PM
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A friend of mine was experiencing the same problems you are having, he also had msd box. He was pulling his hair out trying to find the problem. This past weekend he switched to mopar performance igition with orange box and fixed his problem! He also bypassed ballast resistor. Not sure if that is a good idea but he read in mopar muscle it was ok.?

Re: Ammeter/Main Voltage Fluctuating [Re: Danny] #1144455
02/07/12 08:26 AM
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My reasons for trying the MSD was due to the failures of the orange box and the FBO box.
I will check the MSD box continuity tonight as described in the above thread to see if that is an issue or not.

So how can my alternator field wires be showing 14.0v (VR connected) when the green and blue wires at the VR (disconnected) are only showing 11.9v and my battery is at 12.1v with the key at the RUN position, engine off?
Does the VR raise the voltage going to the alternator?
What else could cause the voltage to go up when the key is at the RUN position, engine off?

Note: I was discussing this with an EE at work this morning and he suggested that I pull the LARGE RED wire from the MSD box off of the battery and then recheck my alternator voltage to see if it goes back down to 12v. He also suggested that if it does, then to try diodes on the LARGE RED wire and the SMALL RED wire (crank/run). If the MSD box is creating the extra voltage, then stopping the voltage from "leaking" may help.

EDIT:
Fact: The blue wire with a white tracer runs from the alternator field wire thru the bulkhead and up the steering column. I then "assume" that it goes to the ignition switch.

The MSD SMALL RED wire is connected to the CRANK and the RUN wires, which are both coming from the ignition switch. If there is feedback (or extra power) thru the SMALL RED wire from the MSD box that is going back thru the RUN circuit, then it appears that it could make it out thru the blue/white wire to the alternator. So in the RUN mode, that might be where the extra voltage is coming from to make the field wire show 14v with the key in the RUN position.

Does this make sense? I am waiting on MSD to clarify if there is any extra voltage coming from the box during the RUN mode.

EDIT 2:
This is the response from MSD when I asked if the MSD box can add additional voltage thru the small red wire:

""Realize that the gauge is 40 years old, you may just have a faulty gauge or a gauge that needs to be reconditioned and updated for a modern, higher current output application such as when the MSD is installed. The older gauges were not engineered or designed for the high voltage and current of a CD unit.

The other possibility is that the gauge is being affected by the multi-spark function of the ignition. The multi-spark function actually fires the plugs multiple times during each firing event at rpm's up to 3,000 rpm.

If it were my vehicle, I would seriously consider having the amp gauge looked at and upgraded.""
-------------------------------------------------------------------------------------------------------------------------------------

I can't see how an old ammeter or a multi-spark ignition can cause the alternator voltage to go up 2v with the engine off.
I am going to add a diode on the small red wire to see that stops the extra voltage.

Thanks a bunch!!

Last edited by YO7_A66; 02/07/12 01:32 PM.

1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
Re: Ammeter/Main Voltage Fluctuating [Re: YO7_A66] #1144456
02/08/12 12:25 AM
02/08/12 12:25 AM
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"Does the VR raise the voltage going to the alternator?"

I readily admit that I have not paid much attention to how the automotive VR works inside, but it needs to alter the voltage to the alternator field in order to control the output of the alternator. If the VR was only able to trim the battery voltage then it would not be able to increase alternator output when the battery voltage was low. So in answer to your question, the VR *can* raise the voltage going to the alternator field.

In your experiment the engine was not running and the voltage was at 11.9. Given that the VR is designed to keep the system at 14.5V, it makes sense that a higher voltage would be presented on the field circuit.

In my opinion, the MSD by itself is not causing the problem, although it still makes sense to do the test you described (in an earlier post you asked why to disconnect the heavy red from the battery before the test; I would do this just to be safe). I run a 6AL-2 and do not experience anything like what you describe. In my car I could notice a definite difference in the load on the electrical system after installing the MSD because my ammeter is now always a bit farther on the charging side (ie alternator is needing to deliver more current due to the extra load) as compared to when I had a chrome box on the car.

I don't have a great suggestion at the moment. I continue to think that there is some sort of high resistance short somewhere in the system. You will likely just need to take a very methodical approach to debugging it. One thing you may want to consider is pulling every fuse that is not absolutely necessary. You could also jumper over the ammeter with a heavy gauge wire and just use the analog voltmeter to see if the condition persists.

Re: Ammeter/Main Voltage Fluctuating [Re: davenc] #1144457
02/08/12 08:17 AM
02/08/12 08:17 AM
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I should also say, when my buddy put the msd in his cuda a couple years ago it was fine. His problem suddenly started one day and he tried everything, checked everything, bypassed ammeter guage, tried three alternators, two voltage regulators, swapped coils, pulled every fuse one by one. He thecked all grounds, he went crazy trying to figure it out. THEN,he put all original parts back on, (alt, volt reg,coil) and ditched msd and went with new orange box and all is well. Sounds crazy?

Re: Ammeter/Main Voltage Fluctuating [Re: Danny] #1144458
02/08/12 09:06 AM
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Dave,
""In your experiment the engine was not running and the voltage was at 11.9. Given that the VR is designed to keep the system at 14.5V, it makes sense that a higher voltage would be presented on the field circuit.""

* Is it normal for BOTH field wires to show 14+ volts or would one field wire show it and the other would not?
Thanks


Danny,
That does not sound crazy and that is exactly what I am going thru. Thank you.


Before I tested adding the diode, I rechecked my voltages again with the key in the RUN position and the engine off. I once again found 14.5-15.5v at "both" of the alternator field connectors while just 12.0v at the battery and 11.9v at the MSD SMALL RED (CRANK/RUN) wire. At the least I am only losing .1v from the battery to the MSD box (CRANK/RUN) connection.

Then I added the diode (400v/1.5a, this does not allow feedback into the CRANK/RUN circuits) on the MSD SMALL RED wire last night and I made some more tests. Now with the key at the RUN position and the engine off, I was getting a voltage reading at the alternator BLUE wire of 11.9v and the GREEN wire of 1.1v. I could not get a reading of more than 11.9v at the BLUE wire after three different attempts (shutting off the key, waiting a few mintues, then testing again). I did not get a chance to start the car but at least my voltages are down.

The theory here is that the Street Fire box (economical street box) may have feedback thru the SMALL RED wire that is connected to the RUN/CRANK 12v feed wires that lead to the key. (Maybe the MSD 6 and 7 boxes do not do this) The key is also connected to the alternator field wire thru the BLUE/WHITE TRACER wire. If the MSD SF box is "leaking" due to the internal capacitors, then it appears that the voltage could be affected all the way back to the alternator. This is why I am testing a diode on the MSD SMALL WIRE to keep any "leaking" from exiting the MSD box and into the CRANK/RUN wires. (see attached)

Note: MSD suggested that I upgrade my current 40 year ond ammeter and my cheepo inside voltage gauge to new Autometer units. MSD said that they talked to Autometer about this which resulted in this suggestion. I wonder if the Autometer gauges already have diodes in them to keep the feedback out of the gauges.

I also made a continuity check on the MSD LARGE RED wire to the MSD housing and got a 0.0 reading. So that looks good.


I won't be able to start the car for a while due to our weather but I just want to see if the battery/alt voltage drops down from 15+ and also to see if the ammeter fluctuation changes.

It is a shot in the dark but I want to try it.

Thanks for the replies.


1970 YO7 A66 [Canadian Export] F8 Challenger
340 (Currently in shop for stroker assy.)
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