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Amp Gauge waving like a beauty queen in a parade

G Guest
I am new to this forum so let me first say "Hello" to everyone. I am the proud owner of a 1972 Detomaso Pantera and a 1991 Ferrari Testarossa, really enjoy both cars. (I wish the Testarossa had the ZF transmission!!!). I am sure this question has been covered before so my apologizes for the repetition. My amp gauge waves like a beauty queen on a float going down main street. I have read on this forum that some people refer to the stock amp gauge as the "Firestarter!". Do I use the "Stunts?" to fix the amp gauge or replace?, and if replacement is the correct approach...What should (TYPE, MODEL#) I replace it with?. Thanks for your input and advice.....Mark.
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racerdaveracerdaveMember
Mark, ALL Pantera amp gauges wave to their owners. Mine has been waving to me for 30 years. It's just part of the "charm" and uniqueness of owning a hand-built car. Embrace it! But do make sure you don't have a loose wire too. Normally the needle only waves under a light load. When the headlights or fan motor are on, the needle should be pretty steady. I replaced my electronic voltage regulator with an original type mechanical regulator and that reduced the waving by half.
I guess you haven't noticed the rear view mirror vibrating yet. And if you have a 72 Pre-L like me, a couple of the dash lights reflect off the windshield at night and stare back at you like two little eyes. But I wouldn't have it any other way! Smiler
davidnunndavidnunnMember
Mark,
If the bouncing needle bothers you, there is an ammeter available that's an exact replica of our Veglia ammeter, but has different internals. It's rated at 100 amps and has an internal shunt, so it doesn't wave at you. The first time I saw it was in a Hall Pantera catalog but I bought mine from Precision Proformance.
wolfgangwolfgangMember
Hi,

I am just checking out the ammeter bouncing thing on #5891. Have already installed a new alternator and regulator during my engine rebuild one year ago. the needle kept on bouncing. I have also swapped the ammeter with another one from a friend´s pantera. no success, also this one bounces in #5891. Have checked the wires; all ok.

Nice waving needle on you tube? Look here: https://www.youtube.com/watch?v=Kws7IUvvoN0
or here: https://www.youtube.com/watch?v=IcW9g6aphTU

So next step would be to install a shunt resistor.
Do you have any experiences which type of shunt should be used? My alternator and regulator are similar to stock types.

Thks all!!
Wolfgang
bosswrenchbosswrenchMember
Wolfgang, the 'shunt' is nothing more than a direct connection across the amp gauge terminals ALONG with the stock wiring hookup. So the current splits and goes thru BOTH the meter and around it. This reduces the needle waving but degrades the accuracy. In the case of the Pantera, stock accuracy is not great anyway. The gauge basically tells you the alt is putting out current; how much is another issue.

My shunt is a simple piece of 0.060" brass shim about 1/4" wide x as long as is needed to stretch from gauge post to gauge post. The larger the shunt's surface area, the less current goes thru the meter. Its a good idea to use shrink wrap or other insulation on your shunt since its carrying a LOT or current!
R rrs1Member
Try a 10 ohm or 27 ohm 1/2 watt resistor across the two terminals. I would also add an 80 amp in line fuse for added protection. All you really want the thing to do is lean to positive or negative to indicate charge or no charge. The amount is not that important. Resistor values will vary. I don't remember what mine was. it might have been 47 ohm. but a few from radio shack should cover it.
rockyrockyMember
quote:
special one because of the massive current or can I just live with


Wolfgang -

The most current you can get across the resistor is I = V/R = 12 / 27 = ~ .3333 Amp

The power in the resistor is P = I*V = 4 Watts

So you should try and find a 5 Watt Resistor. This will probably be pretty big.

Good Luck

Rocky
R rrs1Member
quote:
Originally posted by Rocky:
quote:
special one because of the massive current or can I just live with


Wolfgang -

The most current you can get across the resistor is I = V/R = 12 / 27 = ~ .3333 Amp

The power in the resistor is P = I*V = 4 Watts

So you should try and find a 5 Watt Resistor. This will probably be pretty big.

Good Luck

Rocky


That would be true if the resistor was sharing the load, but it's not. All the current passes through the internal shunt. The resistor only serves to change the behavior of the movement.
wolfgangwolfgangMember
Hi all,
I would like to report concerning my ammeter problem. I have checked all wires again and found out that the wire between the starter relay and the starter was slightly loose. I fixed it properly and could not believe my eyes when taking a look at the ammeter. The jittering was gone and the ammeter displayed as it should....
Hope my experience is useful for other pantera enthusiasts, too....
Wolfgang
jfb05177jfb05177Member
maybe I am going to ask some really dumb questions, but remember I am just learning.

I have read the panterplace and done a little googing and my take is that a large part of the problem could be the mechanical voltage regulator. so is i possible the ampmeter is showing the actual output of the alternator. with the simple design of the veglia being responsive to the the voltage regulator cycling and the normal wire wound shut having enough damping not to show actual conditions. I would think if you had a fast resonse anolog voltmeter, you would see the same waving of 12 to >14 VDC.

so has there been any past changes to the regulator to smooth out the field current to the alternator? I would think adding a filtering circuit, or just a capicitor would solve the problem. But being so simple, there must be something else.

Also, a filter on the diode half waves would take out the high freq ripple

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wolfgangwolfgangMember
JFB,
thanks a lot for your explanations. My car specific electrical knowledge is definitely limited so all your suggestions are more than welcome. I have swapped the regulator today to the standard autocraft again to find out whether the reason of the problem could be the regulator. there is absolutely no difference so most likely buying another one does not make too much sense.
Could you explain a little bit more what I would have to do and what material would I have to take to build in the filter on the diode? Sorry, my question may sound dumb but as said my knowledge concerning electrics is very limited...
Thks a lot in advance, Wolfgang
jfb05177jfb05177Member
sorry about deleting post requesting regulator info...I got distracted and didn't have time to get my thoughts.

I'll restate, I have ZERO knowledge of automotive voltage regulators. It is only what I have read in the last couple years while begining to work on my car.

My original post about filtering was meant to see if the experaince mechanics here have ever modified the regulator to smooth out the "stepping" output of the mechanical design. Given this design has been used on millions of cars, I would have hoped there would have been something already tried and proven.

I plan to study this design and see if I can remember how to design a filter, besides my appearant loss of knowledge about circuits, the other challange will be not knowing any thing about the output of the altenator. If this was a work problem, I would ask for an oscilloscope trace Smiler

the reason for requesting the actual part number is to verify that the currently manufactored regulators are the switching relay design and not the newer transitor controlled.

By chance would the pully ratio be known so I would have some ideal of what the primary output frequency would be.
jfb05177jfb05177Member
also, given all I have is the pieces, I need a little information to help me think about this

where would be the easiest place to get connection to the wire from the altenator and the gauge. a location as close to the amp gauge would be best.

something intersting, I went and measured the ohms accross the terminials of my amp gauge and was surprised that I had 50K ohms. since it was 30+ years, not sure if it had been modified prior to me or internal corrosion. has any one every measured thiers. I was expecting a couple ohms

I found my blue regulator and when I have the chance I plan to take it apart to see what is in there

the more I watch the utube, the more it looks like a problem with the regulator (or its wiring). a couple questions
Does your speedometer "battery" lamp come on with the key to run (but engine not running)
If the "battery" lamp flickering, especially when the amp goes negative.

the scenerio I think I am see is when the amp gauge goes negative, full field is then applied via the voltage sensing relay. with full field, the amps go in positive direction till it maxs out. then the voltage sensing relay starts to "regulate" from full to no current, but never goes to the half current "double open" relay state. then the voltage relay goes to no current and the amps fall negative and the cycle starts again.

while this is what I think I see, I will need to think more and see if I can find a wiring failure that would cause when new components are installled
S stevedMember
Interesting comments about the voltage regulators. I feel that I was treating a symptom and not the cause when I changed the ammeter. When I have approx half tank of gas, it sure looks like I can see the same frequency of movement on the gas gauge as the ammeter;it is a very slight movement and I have to concentrate to see it but it is there even with the now dead Hall ammeter.I don't seem to notice that movement when the tank is full.
Steve
rockyrockyMember
I must second the observation that loose connections in the "system" have the ability to cause the Ammeter to "wave".

When I bought my car, the ammeter was exhibiting this behavior. The PO stated that it was something new, that he hadn't seen before.

I observed that when I tightened my loose positive battery terminal, the behavior stopped.

Wolfgang noticed it quit temporarily when tightening up a different connection.

I am interested in the fact that it can be observed on the gas guage as well.... All fascinating pieces in this puzzle...


My OPINION is that the cars did not do this from the factory, but the wiggling most likely will correllate to the frequency of the mechanical voltage regulator. Has anyone swapped out the mechanical voltage regulatior with a solid state one and observed the results?

Does anyone know if the solid state regulator is a "bang-bang" (on-off) kind of thing, or a more smoothed application of charging voltage?

Thanks -

Rocky
Last edited by rocky
jfb05177jfb05177Member
I need to bow out as a contributor to solving the problem. In my humble opinion I "think" you are seeing a regulator problem like others stated my be a loose/coroded connnection. I would suspect the voltage sensing wiring from battery. starter to regulator.

while I would try the mods I have thought about, with out validation and monitoring they could result in damage.

I am not sure that the condition you are experaince is not damaging things now any way.
I would want to confirm that the current is truely that erratic with other meter or via sensing voltage as a concequentional effect

again, first thing would be verify the wiring to the regulator is good.

If you are using the mechanical voltage regulator as assumed, I wonder if the new produced are actually set up correct from the factory and maybe they require calibration prior to use
wolfgangwolfgangMember
JFB,
the battery lamp is on when engine off and ignition on.
the lamp does not flicker when the amp goes negative.
I have a rather new aftermarket regulator and the - most likely - original motorcraft DT3F-10316-AA. Have tried both; no difference visible on the ammeter.
Have put on an additional ground connection from the regulator to the chassis. No change as it seems when starting the car in the garage but I have to do a test-drive during the next days to check this out better.
jfb05177jfb05177Member
I had no luck googling that part number. Do you know if the regulator is mechanical or transitor type?

besides extra grounding reguloator, I think the altenator should need a good ground also. having the wires go to the same point on the chasis would be good. I would also look at the wiring providing the voltage to the regulator. It should be coming from the large cable to the starter terminal.

Do you have a test meter to see if there is AC volatage on top of the battery DV voltage.
also could you do a charging voltage test where you first measure just battery, then when at above idle, then with all loads on
jfb05177jfb05177Member
that "looks" like it would be mechanical.

If you were aware, the way the mechancal works is if the voltage is low (say below 13.5VDC) the altinator goes to full charge. once the voltage reaches say 14.0VDC, the regulator steps the altinator to half charge. so the relay inside that does the switch cycle rate depends on the electrical load, if there is a little, the cycle rate is with more half output. if heavy load there is more full output.

from a control engineer perspective, this is the same as the modern digital controled regulators with "pulse width modulation". However that design uses capacitors to "smooth out the steps from high to low to provide a more anolog type like the in between transistor design
R robbieMember
I thought the wavey amp meter needle was because all the charging system current goes through the meter so it over-reacts to changes in demand and the voltage regulator actions. The fix is to make a copper shunt that goes between the two terminals on the back of the gauge. Size the shunt so it carries most of the load but some goes through the meter so it registers slightly. This dampens out the waving. Someone correct me if I got that wrong. I think decades ago I did that to mine but the years cloud the brain.
J jffrMember
quote:
Originally posted by Robbie:
I thought the wavey amp meter needle was because all the charging system current goes through the meter so it over-reacts to changes in demand and the voltage regulator actions. The fix is to make a copper shunt that goes between the two terminals on the back of the gauge. Size the shunt so it carries most of the load but some goes through the meter so it registers slightly. This dampens out the waving. Someone correct me if I got that wrong. I think decades ago I did that to mine but the years cloud the brain.


You are 100% correct!
jfb05177jfb05177Member
adding a shunt to reduce the current through the meter movement would take a current that is actually waving from 10 to 15 amps (5 amp wave) and send only 1/2 of that to the meter so it shows only shows a current or 5 to 7 1/2 amps and thus a 2 1/2 amp wave. So you would not see the waving, but the battery and the car's electrical still do. (the waving shown on wolfgang's utube is much more severe than what I would expect from a mechanical regulator)

******

I have been "Learning" about mechanical voltage regulators just from sifting through google info and have a question I hope some one would know the answer.

some discriptions state there are 3 charging levels, ie full, half and zero field current. that is the voltage relay contacts are either closed, open or grounded. other discriptions state there are 2 charging levels, ie full or zero field current. thus the voltage relay contacts are closed or grounded.

being a mechanical by trade, I never realy fully grasp Kirchhoff's current summation rules, but I can not see how the voltage divider used to provide voltage to the voltage relay's coil could work with the 3 level discription using the schematic provide by PanteraPlace. using the 2 level of charging works fine. I have found other schematics that does keep the voltage divider simple even with 3 level charging.

SO, does the Ford mechanical regulator have 3 or 2 charging levels?
wolfgangwolfgangMember
quote:
Originally posted by Bosswrench:
Wolfgang, the 'shunt' is nothing more than a direct connection across the amp gauge terminals ALONG with the stock wiring hookup. So the current splits and goes thru BOTH the meter and around it. This reduces the needle waving but degrades the accuracy. In the case of the Pantera, stock accuracy is not great anyway. The gauge basically tells you the alt is putting out current; how much is another issue.

My shunt is a simple piece of 0.060" brass shim about 1/4" wide x as long as is needed to stretch from gauge post to gauge post. The larger the shunt's surface area, the less current goes thru the meter. Its a good idea to use shrink wrap or other insulation on your shunt since its carrying a LOT or current!


I have already installed a shunt as specified by bosswrench but unfortunately this does not prevent my ammeter needle from bouncing around.
bosswrenchbosswrenchMember
As JF said, the simplest way to cure this- if it bothers you- is to tighten ALL the connections, especially the multiple grounds and add a shunt across the amp gauge terminals. This is a fix that came out when the Pantera was still being sold by Ford, so needle-waving is not new and probably is not harmful.

The second fix many use is to use an internally regulated modern alternator and discard the separate regulator. That way there is zero question as to whether the regulator is solid- state or uses contact points, and it has the advantage of allowing a bigger alt. If you do this and go to a simple-to-install single wire alt, some need the idle rpms set up higher to begin charging at low rpms. Other single-wires do not; ask before paying.

The stock Motorcraft alt was 47 amp (some identical appearing were 61 amp,) and both are simply too low in output to supply AC, headlights/tailights/stop lights, a stereo & CB and other accessories, at low rpms in heavy evening traffic. Owners have had the engine die in traffic jams and then find they'd been running on the battery for some time & do not have the juice to restart. Tow trucks love evening rush hours....
jfb05177jfb05177Member
wolfgang, do you have access to a voltmeter?

from your utube, I think you might have a bigger problem than the normal amp meter waving.

from what I have read recently, IF it were me, given I sort of know how alternators/regulators work, I would put a swtich and one of those small audio "stiffing" capacitor on the altenator field terminal. those caps are about $10 at an electrical parts store. But with out watching voltage you could over charge the battery.
jfb05177jfb05177Member
proceed at YOUR OWN risk!
I would first try a 0.1 F (1000uF), it needs to be rated above 20VDC. using a switch so I can put it in service and back out quickly if needed. it woulg go on either end of the wire going to the altenator field and the other end to ground.

the cap would act like a fast charge/discharge battery. so when the regulator steps the field current to max, the cap charge will cause it to ramp. when the regulatos steps to zero, the cap will cause the current to ramp down.

the time of the ramp depends on the cap size and the resistance of the circuit. from some online info, I think there is a 50 ohm resistor on the field wire to ground. thus with a 0.1F, the ramp from 0 to 80% will be 0.05 secs. this would reduce a charging cycle frequency of 3 htz and greater.

PS...
I found a good writeup on how to test the regulator.
http://www.fordification.com/tech/charging.htm
towards the bottom of the page there is instructions on disconnecting the regulator and using a jumper to apply full field. IF the amp meter is waving with the jumper (and the belt is not slipping) I would think the problem is bad connections in the wiring
Last edited by jfb05177
wolfgangwolfgangMember
In the meantime I have put a separate ground from the regulator to the chassis. The result is very positive; the bouncing needle has calmed down considerably. I still have some bouncing at low revs and the next step will be to buy a new connector plug (correct wording????) for the regulator in order to have good connections here, too.
If I have no success with that I will try out the "JFB-checking procedure"!
I`ll report!
jfb05177jfb05177Member
Good to hear you got the center to full scale waving reduced. from what I surmized, the minor bounce sounds like it would the regulator switching from full field to half field now. Charging voltage should be right at normal.

the check out procedure while at idle (where you now see the bounce) of forcing full field current should stop the bounce, But if idle is where the regulator is trying to reduce voltage, going with the full field jumper will raise the voltage and begin to over charge the battery, so monitor and keep the duration to a minimum (30 minutes if voltage is say less than 14 VDC, less if greater)

the minor bounce at regulator switching is a good canidate for a smoothing capacitor
jfb05177jfb05177Member
I can imagine the operation of the altenator and regulator be sort like

from idle up to X rpms, the regulator will be the full field setting given the output of the altenator is very speed dependant. at idle, the charging voltage will be low and as rpms increase so will the charging voltage up to the desired value.

when greater than X rpms, the regulator has to start switching between full and half field to keep the desired charging voltage. as speed increases the switching will stay longer at the half field state up to the speed Y in which half field alone is sufficent.

I don't think there will be much of a speed range above Y where the regulator stays purely at half field, but will start switching from half to no field. My anysis of the circuit does cause me to have questions when this occurs as it appears the relay to switch from self feed back to battery feed may occur when zero field switching. so maybe there is some built in dead band to have a high rpm zone with just half field and zero field only needed at extreme high RPM

IF you care to take some data
----RPM------|--VDC--|--VAC--|--Freq--|--ampmeter wave--|
(every 200)..............................................yes/no

Thats just my two cents

these types of questions makes me wish I had started the rebuild on mine when I had access to vast diagnostic instrumentaion
wolfgangwolfgangMember
JFB,
I still have to do the checking process you have suggested. Will do that asap.
I have built in a new 4pin system connector leading to the regulator as my old connector really looked pretty worn. Unfortunately no success.
While doing that I have noticed that a suppression capacitor is connected to the regulator. Any idea whether a bad capacitor could have to do something with my bouncing ammeter needle? I could not find out the exact type of the capacitor....
Wolfgang
jfb05177jfb05177Member
I don't know for sure. the normal "radio suppression" cap is on the Yellow supply wire from the battery to the field. I think its purpose would be to filter out the radio wave noise caused by the regulator switching field current on and off at 100 hz. I don't see how it could effect the altenator output current.

Is your cap on the yellow?

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