hi guys, need your help again. i just installed a new amp meter went to hook up my battery and had bad sparks from the post . took my 12 volt test light to check for short , found by disconnecting the amp gauge it showed no short . what i need to know is if anybody has a diagram showing the correct wiringand how the gauge should be insulatatedto the gauge cluster. i no someone out there knows what i am doing wrong.thanks alot

Well, let's hope you did not hook it up as a voltmeter, and wired one post to ground, this WILL produce sparks.

I will start at a hypothetical place to start wiring the ammeter.

Let's start at buss bar on horn relay.
1. Locate the red wire going to the battery via the junction block on radiator support in front of battery. While you're there at battery, disconnect ground cable from battery.
2. Disconnect this red wire, the other wire on the buss bar goes to the firewall.
3. From this disconnected wire, attach a terminal lugged wire, same wire gauge as red wire, wrap connection in electrical tape and/or shrink tubing, and run through firewall (protected hole), attach to a terminal post on ammeter.
4. Take same gauge wire, put terminal lug onto it and attach to the other ammeter post.
5. Run this wire back to same spot on buss bar and attach to where previous wire was just removed.
6. Hook up battery ground cable. Turn on ign key to run position. Watch gauge.
7. If gauge shows a positive charge, swap two wires on back of gauge. Otherwise, job is done. Turn off ign key.

Hints, Use crimp lugs and crimp them very well. It would be better to solder lugs to the wire and crimp them. Remember, these two wires are going to carry the electrical load for the car AND its accessories from the battery, so minimum wire gauge is #10, multi strand. Make sure buss bar is clean of rust.

Shouldn't have any problem. Hooking up the ammeter at this place will show discharge/charge of the battery. One could do the same and hook it up to BAT post on alternator to see alt output. Personally, I like to see the charge of the battery, so as I can tell the state (age) of the battery.

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Everett 68/350/PG/11.90/115mph

[This message has been edited by Everett#2390 (edited 08-02-2002).]

i guess my question know, is this car has all new wiring harness's from factory fit i.e light, engine and under dash with console gauges. shound this just be a plug in step. if not what should i do next. thanks

I would think this would be a Plug-n-play deal.

Are you sure the posts on the ammeter are isolated from ground when the wires are installed?

Usually, there are insulating washers on the posts to isolate the meter from ground.

Everett

Everett,

Plese correct me if my memory isn't working but I thought the factory console gauge used a different system for measuring amperage. Your traditional in-series description is correct but on my console gauge system one gauge wire connects to the horn relay, the other to the battery junction block. The gauge translates a voltage difference?? to a amperage reading or some such thing.

The wiring supplied for the gauge could not handle the loads supplied by the alternator if installed in-series.

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The Red Beast http://www.geocities.com/casanoc

CarlC,

You are probably more than correct on the console gauge. I was giving instructions for a series wired ammeter, more of the aftermarket type rather than OE type.

They would be using the shunt method in measuring the current load. Measuring the voltage drop across a parallel high resistance circuit and indicating amps on the gauge face.

And finally, Yes, the meter would not be able to handle alternator loads.

I totally screwed this post up, didn't I? Nowlin1, please forgive me.

Everett

Nowlin1,

As Everett was describing, the gauge terminals should be insulated from ground. You should be able to use an ohm meter to determine if either of the wires is shorted to ground. If both wires check out, and the gauge posts are inslulated, then perhaps the gauge is bad. I don't know if the gauge body requires grounding to function. Everett?

Everett,

Since you know how these things work, I have a question concerning them.

If I understand correctly the shunt-type gauge measures the voltage drop across a lenght of wire and it is translated on the gauge to amps.

On our cars the wire used is the length from the horn relay to the battery junction block. My wiring diagram is buried in the garage but I believe this is a 10ga wire.

What happens if a larger gauge wire is installed? I upgraded to a 6ga wire when the 105 amp alternator was installed (I had a bunch of 6ga laying around). Even before the new wire was installed there was little gauge deflection, and with the new wire it's almost non-existant. With the lights, fan, brakes, etc. on (trying to create full system load) with the engine off there is still little gauge deflection.

Is there a method to calibrate the gauge, or some different way to hook it up so that the gauge reads properly? What's the best way to determine if the gauge is even working?

Thanks for your help.

Carl

[This message has been edited by CarlC (edited 08-05-2002).]

thanks a lot for the information. i do have a multi/meter, but do not know how to check for a short. any information will be greatly appreciated. thank you again

CarlC,

The gauge body would need to be grounded for the purpose of illumination if the light socket has one wire verses two wires. If measuring resistance from any one post to ground (case) of the ammeter, I would believe the ohmmeter should read an open.

Yes, there is a way to calibrate the ammeter to read close to the approximate correct reading. But first, using an external ammeter, measure the amount of current flowing for calibrition purposes later. The closer to a whole number, i.e., 5, 10, 15, etc. the better.

You are correct in giving the symptom of "less" meter deflection when upgrading from 10 AWG to 6 AWG, the bigger the wire gauge, the less resistance to current.

The first method involves math. Read the meter. Hopefully, there is a statement on it suggesting the amount of current needed for full scale deflection, i.e., FS=200 ua (microamps, 1X10 minus 6 power), Ohm's Law states, Resistance = volt divided by current. 14 volts/200 ua= 70,000 ohm resistor affixed across the meter posts.

Another method is to attach in parallel across the ammeter terminal posts, a resistor decade box borrowed from an electronics friend. Crank in the highest resistance, 99,999,999 ohms. Turn on ign key or lights and decrease resistance until the approximate calibration amount of current is showing on ammeter. Then purchase from Radio Shack or from your electronics buddy the closest resistor to value needed and attach it across the ammeter terminal posts. This is providing the shunt wires are already there from the junction block and horn relay.

A schematic or wire diagram of the car would work great. I'll check my Motors Manual for help. My Chiltons here at work does not include console gauges.
Sorry to be short, but,I must go now. Get back with you real soon.....

Everett

Thanks Everett. Sounds similar to calibrating a temperature gauge.

My gauge does not have a deflection rating.

I don't have a decade box so could I try a few trim pot's (10M, 1M, etc.)? They are only a $1 or so at the local surplus house.

I also question if a fuse should be used on one of the leads. If the main conductor from the battery junction box to the horn relay failed (burned or fusible link) would full current try to pass through the gauge and wreak havoc on everything?



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The Red Beast http://www.geocities.com/casanoc

Nowlin1, since you have a DVM, you on your way.

To check for short to ground, select ohms on the meter, tie one lead to ground, and use the other probe to search for a short to ground. If the meter reads very close to zero, sometimes less than 15 ohms, its considered a short to ground, unless a light bulb is in the circuit. This would be a short to ground.

There is the possiblity of a short to another circuit, not necessarily to ground. Use the meter the same way, but probe other circuits to find continuity to another circuit. When one is found, and the diagram does not show the two circuits being tied to each other, then it is considered to be a short to another circuit.

Important -- When making continuity checks, ohms scale, is it suggested there be no voltage on the circuit being checked. DVM's will continue to work if by mistake a voltage is on the circuit. Some of the older analog meters pop a fuse, trip a circuit breaker, or just break.

Nowlin1, I suspect maybe a wire in the wrong place somewhere. I don't have a diagram of the circuit, and, unfortunately, I'm not there to look and probe with you to pinpoint the problem. I would suggest to you to sit back, get the diagram out and carefully go over the car and compare to the diagram. It's labor intensive, but, sometimes this is what must be done. You could go to the Public Library into the Reference Section and look up the electrical wiring diagram of the car and reproduce it for a little change.

Nowlin1, one thing you should do, are there any doors opened? Meaning dome light on? You disconnect the battery, did some checking, then, hooked up the battery and drew sparks.
You might take your DVM and use it as an ammeter. It will have an DC amp function and you can hook this ammter between the battery post and battery cable to see the current draw. Don't fret about pos or neg current reading as shown by the meter, you're just looking for the numeral amount of current flowing. Your DVM is fused for 10 amps inside, so if its over 10 amps, fuse blows open. If you find minimal amount of current, say a couple amps, this could be a light on, (glove Box is always good for this). If you find more than 10 amps, then I'd pull every fuse out from the fuse box, substitute a circuit breaker for the DVM ammeter and install one fuse at a time to find the faulty circuit. When the circuit breaker trips, there's your faulty circuit. Start from there.

Hope this helps out, Nowlin1. I know you're looking to get your ride on the road.

CarlC, yes you can use one of those pots, I'd probably use the 1Meg. As for the fusible link burning out and max current going through the gauge, I kindda doubt if that event would ever happen. The reason I say this, by reading your post on the wiring, the console gauge circuit is as follows; leave a terminal post on the gauge go to the horn relay. The other post goes to the battery junction block. The shunt for the meter is the length of these two wires PLUS the #6 AWG wire between these two points. If one of those two wires opened, the circuit would be open, gauge would be dead (out of circuit now). But, if the #6 AWG wire were to break, burn, etc., then yes the meter will be toast, until the one of the two smaller wires burned open first, then its an open circuit after that. Makings for a bad day.

I hope this helps for the both of you, Everett

Ps Had to correct my spelling.....

[This message has been edited by Everett#2390 (edited 08-06-2002).]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Everett#2390:
CarlC,

The gauge body would need to be grounded for the purpose of illumination if the light socket has one wire verses two wires.<HR></BLOCKQUOTE>

The guage body of the Ammeter is not grounded in a 68/69 Camaro console gauge set, but the metal mounting plate the guage (and the lights) sits in is grounded. Thats so the lights will work. The ammeter has a phenolic insulator behind it, and plastic orings on the studs to keep everything from touching this mounting plate.

Heres a picture: (the other gauge (right of picture) is the temperature gauge)
http://www.townisp.com/~markcanning/camaro/gauge1.jpg

There is no way to calibrate this gauge except by adding external resistors to one or both of the leads to the gauge. If you have changed your main charging wire from the original 10 gauge to 6 gauge you have thrown the "calibration" (use the term loosely) of the guage as you are changing the shunt resistance of that portion of the gauge. I would expect the guage will hardly deflect now either under charge or discharge as you have probably 1/2'ed the resistance of that length of wire. The guage is really just used to indicate a charge or discharge of the battery. I've never seen mine move much more than 2 or three needle thickness's to the charge side, no matter how low the battery charge is, and most of the time it sit's about 1/2 needle width to the (+) side of the gauge.

Each lead has a fusable link in it near the end of each lead.


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Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11
My 69 L48 - 350/300HP Engine (http://www.townisp.com/~markcanning/camaro/transparent%20air%20cleaner3.jpg)

Thanks guys.

I'm getting a little confused here. When calibrating the gauge should the resistor go in-series with the shunt or attach in parallel across the gauge lposts?

I'll check my aftermarket console gauge setup and check for a fusible link(s). I don't remember seeing one but it's been a while since I've peeked at it.

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The Red Beast http://www.geocities.com/casanoc

The part you changed is parallel to the gauge. You can't put another esistor in parallel with the gauge since that would further reduce the total circuit resistance To fix it you would need to be in series with the gauge, the easiest place is inline with the battery terminal side lead wire.

Were not talking a lot of resistance. 1000 feet of #6 7 strand copper wire has a DC resistance of about 0.491 ohms. 1000 feet of #10AWG 7 strand copper has about 1.24 ohms.

How much wire is between the battery and the Horn Relay, maybe 7 feet. That's .003437 ohms for the #6 gauge wire, and .00868 ohms for the #10 gauge wire. If we assume the gauge can actually indicate plus or minus 60 amps with the # 10 wire (which would melt the wire as a #10 is only good for about 40 amps (by NEC) , maybe 60 before it actually starts to melt).

The resistance associated with 60 amps across the #10 wire results in voltage differential of about 0.52 Volts. With the #6 wire it's 0.20 Volts.

If the gauge is linear that works out to about 0.08 Volts per 10 amps of indicated current with the stock setup. roughly equal to 1 millivolt per amp. Your gauge will only indicate plus or minus 25 amps ((.20/.08)*10 ) for a battery charge (or discharge) of 60 amps (full scale meter deflection).

These gauges are essentially 1 volt range millivolt meters. +0.5 volts deflects the gauge one way -0.5 Volts deflect it the otherway. They indicate trends, and were never intended to provide indication of a specific amount of current flow.

Without knowing the resistance of the gauge itself it would be hard to figure out what resistor would work to bring the meter back into "Calibration". But it is going to be very small, somewhere in the milliohm range (.005 ohms) I wouldn't worry about it all that much.


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Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11
My 69 L48 - 350/300HP Engine (http://www.townisp.com/~markcanning/camaro/transparent%20air%20cleaner3.jpg)

[This message has been edited by Mark C (edited 08-06-2002).]

[This message has been edited by Mark C (edited 08-06-2002).]

As Mark suggests, the gauge is to fill a void in the console and not really met to be taken for a quantitative measurement. Thank you Mark for clarifiying and for the installation mounting of same gauge.

If one wants to know exactly how much current is flowing, then one should use an aftermarket gauge with it wired in series with the charge wire.

Your new resistor would be in parallel to the meter, across the two posts of the meter.

Would I re-calibrate the meter? Probably not.

Everett

Revised to change resistor location from parallel to series circuit:


The part you changed is parallel to the gauge. To fix it you would need to be in series with the gauge because any further resistance added in parallel will decrease the total circuit resistance. The easiest place to do this is at the battery post terminal.

Were not talking a lot of resistance. 1000 feet of #6 7 strand copper wire has a DC resistance of about 0.491 ohms. 1000 feet of #10AWG 7 strand copper has about 1.24 ohms.

How much wire is between the battery and the Horn Relay, maybe 7 feet. That's .003437 ohms for the #6 gauge wire, and .00868 ohms for the #10 gauge wire. If we assume the gauge can actually indicate plus or minus 60 amps with the # 10 wire (which would melt the wire as a #10 is only good for about 40 amps (by NEC) , maybe 60 before it actually starts to melt).

The resistance associated with 60 amps across the #10 wire results in voltage differential of about 0.52 Volts. With the #6 wire it's 0.20 Volts.

If the gauge is linear that works out to about 0.08 Volts per 10 amps of indicated current with the stock setup. roughly equal to 1 millivolt per amp. Your gauge will only indicate plus or minus 25 amps ((.20/.08)*10 ) for a battery charge (or discharge) of 60 amps (full scale meter deflection).

These gauges are essentially 1 volt range millivolt meters. +0.5 volts deflects the gauge one way -0.5 Volts deflect it the otherway. They indicate trends, and were never intended to provide indication of a specific amount of current flow.

Without knowing the resistance of the gauge itself it would be hard to figure out what resistor would work to bring the meter back into "Calibration". But it is probably tiny, somewhere around 0.005 ohms in series with either leg. I wouldn't worry about it all that much.



[This message has been edited by Mark C (edited 08-06-2002).]

This is what make this site great. Where else is this kind of quality information, feely exchanged, available to us gearheads? Thanks guys, and thanks to Al and DjD and the other moderators for supplying such a forum.

Sounds like getting the calibration right given the small amount of resistance required would be a PITA. Perhaps it's time to look into retro-fitting some type of voltage meter into a re-numbered stock silver gauge face. That would at least tell me when there is a discharge condition. As it is now I can't tell what's going on until the battery is dead.

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The Red Beast http://www.geocities.com/casanoc

as CarlC said, this is what makes this site so great, with all you guys out there willing to share your expertiece with other people you dont know personally,is just great. i know with the information i have recievedi will have my car going soon. again thank you all verymuch.

Hmmm. Interesting idea, Carl. I have a dead original amp meter that could donate the face! I had bought a repro replacement but now it seems a waste of space. Originality isn't the issue as I would like some meaningful input ( like a loss of battery charge!)

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Rick Dorion
69 RS Conv,355,M20,4.10's and I don't worry about stone chips ( yet ).

Rick,

I've already done this with the temperature gauge. I could never get the stock one to work correctly so an Autometer (movement only attached to the stock face) went into the stock gauge's position. The sweep angle is the same and I taped the Autometer gauge face onto the inside of the glovebox just in case things start to get warm. 180* is at 12 o'clock so it's easy to remember.

Autometer also has a 2 1/6" voltage gauge, 8-18v, with the correct sweep angle to match the factory silver face angle. That puts 13v at 12 o'clock, so if the charging system goes down, that's going to cause the gauge to sweep into the dischage, and vice-versa for when the car is running at 14v. Looks like I have a new project.



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The Red Beast http://www.geocities.com/casanoc

The temperature gauge is a little different in that it is similar to the fuel gauge and it has a feedback coil within the gauge, to drive the needle downscale as the engine cools off.. The sender is essentially a potentiometer, just like the fuel sender, Resistance decreases as temperature increases which increases the current flowing thru the gauge, which moves the need upscale. The feedback coil has a fixed 82 ohm resistor on the back of the gauge so the amount of counter EMF generated in the gauge coil is constant. Most of these temperature gauges seem to indicate about 1 mark above 1/4 scale at 180 degrees. I replaced my fixed resistor with a 0-500 ohm 10 turn precision potentiometer and set it to 91 ohms. This makes the temperature gauge indicate 1 needle width below 1/2 scale at 180 degrees. Seems to make the gauge more usable. Some day I'll hunt down a fixed 91 ohm resistor (remember most are +/-5% and a couple of ohms makes a difference)and replace the pot, but it's not high on my list of things to do yet.

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Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11
My 69 L48 - 350/300HP Engine (http://www.townisp.com/~markcanning/camaro/transparent%20air%20cleaner3.jpg)