ronarndt

If you mean the fan motor for the car heater, I did not try that. I used your system of checking current draw with all of the normal electrical components on, but did not turn on the heater fan. I had the fuel pump, radiator electric fan, radio, turn signals and low beam lights on and still had positive charging measured at the battery + cable. Only when I started the car did it show a discharge when the starter motor was running, then after the starter motor stopped, went into a positive charge of about 10 amps for 30 seconds, then settled down to a low positive charge of about 1-3 amps measured at the battery cable. The ammeter follows this pattern, but its reading when everything settles down is on the negative side of the gauge. Maybe the gauge is off. All of the other instrument panel gauges I replaced said GM replacement on the box. The ammeter had some brand I had never heard of on the box- probably Chinese.

DUB

Yes I was referring to the fan blower motor for the A/C-heater.

I by no means a gauge restorer or a person who knows everything inside a gauge.

So I always call and talk to my gauge guy who fixes them for me and ask him if he sees or had noticed anything weird about these aftermarket gauges.

Often times he comments on how the aftermarket gauges are not as good as an original and it is best to get it serviced due to the quality of the gauge itself.

Being on the negative side of the gauge draws concern....and it adding 1-3 amps does have me concerned also. It does not seem like that is enough. But what do I know...that 1-3 amps of charge may be enough.

DUB

ronarndt

Thanks for your help. I may have the gauge checked. In my real job I was director of manufacturing for three pharmaceutical companies. I had a department whose full time job was checking scales, balances, timing devices and gauges to see if they were accurate or if a correction factor had to be calculated to satisfy FDA regulations. I may call in a favor and have my ammeter checked against one that is calibrated against industry standards.

DUB

Glad that you have a resource to do this for you.

All I know is that I would have to call my guy and talk with him and see if he has experienced anything crazy like this.

DUB

ronarndt

black and black/white stripe wires to ammeter

I phoned one of the technicians who used to work for me and first thing he asked about was the gauge of the wire that burned out and what I replaced it with. The black/white stripe wire burned out so badly that I could not tell what gauge it was. It looked like 16 ga, so I ran a completely new 16 ga wire from the ammeter to the horn relay terminal, finishing the circuit with 20 ga fusible link wire at the horn relay.
Today I checked the old fuse block that I removed when I installed the new wiring harness two years ago. I found the black wire and black/white stripe wires going to the ammeter. The black/white stripe wire is 14 ga, not 16 ga like I thought, so I had too small a new wire, which messes up the ampere flow to the meter. I need to rip the dash apart again and replace (again) the black/white stripe wire. I have 14 ga wire, but had to order the 18 ga fusible link wire, so it will be next week to see if this fixes the problem. Fingers crossed.

DUB

Hate that you have to do this but I feel you know that you found the 'smoking gun'.

Once repaired. I still would be curious if the alternator on the engine now has enough umph to keep the system charging with the added electronics that have been added to it.

DUB

The13Bats

On my 69 with at the time i had a 80s firebird alternator that was about 100 amp and Taurus 2 speed fan, it was marginal,
I didnt have any other stuff drawing besides coil and at night lights,

lionelhutz

Powering the fan and electric fuel pump from the battery means that the ammeter can not show negative when it is powering them. If the alternator doesn't keep up when powering them, then the battery supplies the extra current instead. This current drawn from the battery doesn't register on the ammeter since the connection is right at the battery.

In other words, the ammeter doesn't show the sum of the battery + alternator currents powering the fan and fuel pump but only the alternator output current that is reaching the battery and which might be powering them. The current reaching the battery could also be re-charging the battery.

The ammeter should not show negative if you cold start the car so nothing else is on but the fuel pump.

I doubt the difference in wire size going to the ammeter would affect the ammeter reading very much, and it 100% can not cause the meter to read the in wrong direction. For the most part, the ammeter actually measures the voltage drop across the 10 gauge charging wire it's connected to.

Still, the ammeter circuit is a fairly low resistance, so decent current levels do flow through it. Decent, but still not nearly as much current as the 10 gauge wire has flowing through it. I don't recall the resistance numbers, but the current ratio might be something like 20:1. In other words, 1A flows through the alternator for every 20A flowing through the 10 gauge charging wire.

I'd suspect your ammeter is simply off.

It sounds like you have a clamp-on ammeter, so put that ammeter on the 10 gauge wire between the 2 wires going to the car ammeter. Compare the readings. You could probably move the needle on the ammeter if it's off.




The current for the fan still has to flow through the fusible links even if the fan is powered from the battery or starter solenoid.

ronarndt

ammeter in 68 Convert with correct wiring on ammeter circuit. Idle speed

Today I installed the correct 14 ga wire and 18ga fusible link on the black/white stripe side of the ammeter circuit. Everything now works as it is supposed to. Had I carefully checked the wire size when I first replaced the wire I would not have wasted time. Attached is the gauge with the car idling. It runs thru the normal cycle when I start the car. 1) momentary discharge while the starter is running, 2) momentary strong charge after the starter motor stops and 3) needle settles down to zero. For those discussing theory, the ammeter is designed to expect a certain current flow in amps on both the black wire and black/white stripe wire to maintain a zero reading on the gauge. When I used a smaller wire on the black/white stripe side of the gauge, less amps were delivered on that side of the ammeter circuit, it upset the baseline amps balance and made the reading incorrect. If I had not saved the old fuse block, I would not have been able to confirm the correct wire size and would still be scratching my head. At road speed and approx. 2000 rpm the gauge stays around zero with fuel pump, electric radiator fan and headlights on. At idle speed with these devices on, there is a discharge of about 2-3 amps. I still hate working on stuff behind the dash on these cars.

DUB

If you are happy I guess that is all that matters.

I myself..if I were repairing it for you...would not give the car back to you until when all electrical components that can be on and run...are running at idle and there is no discharge.

DUB

lionelhutz

Good theory, but it's wrong. The ammeter is basically a coil of wire connected between the 2 wires that connect on the back. So, the current that flows in one of the wires MUST be equal amplitude but opposite direction to the current flowing in other wire. The only way to not be true is having a bad meter with an insulation failure allowing current to improperly flow to ground.

You probably accidentally fixed it, possibly by fixing a bad connection you din't know was bad or you pegged the meter so hard the needle moved on the armature so it points to charging now instead of discharging even when the armature is in the same spot.

carriljc

If the car is wired correctly and you're indicating a discharge at idle, THEN you are NOT adequately maintaining the battery charged.

lionelhutz

I looked at your post again. The meter should show around 20A with the fan and fuel pump connected directly to the battery and running. The meter shows the current flow to or from the battery and since those are powered from the battery the meter should show the current required to power them coming from the alternator and giving a positive reading. So, the meter is still not working correctly.

ronarndt

DUB- there is only a slight discharge at 600 rpm. As soon as the rpms go up the alternator is spinning fast enough to keep up. Keep in mind I have only driven the car once at night- so it never really has the headlights on and without them on there is plenty of juice. If I add some other electrical stuff, I'll get a bigger alternator.

ronarndt

lionel- the gauge I installed incorrectly (insulating strip installed incorrectly) dead shorted and burned out the fusible link two years ago. I drove the car without a working ammeter for two years, since the battery maintained charge. This month I replaced the fusible link with the wrong gauge link and this time the dead short and the wrong fusible link melted the entire black/white stripe wire. When I took the dash apart, I discovered the incorrectly installed insulating strip which allowed the gauge to ground out to the dash panel. I replaced the Black/white stripe wire with 16 ga, since that is what the remains of the melted wire looked like. I finally found the correct ga for that wire is 14 ga, so that is what I finally installed and now the gauge works. 12 v going thru a 16 ga wire gives less amps than 12 v going thru the correct 14 ga wire and affected the reading.

The13Bats

Ron
You only need to please yourself, if you are happy with what its doing run with it,

"IF" the day comes you find the draw too much then think about a bigger amp alt,

lionelhutz

That is still not how it works, no matter how many times you write it. It is NOT possible to have a different current in each wire due to the way the meter is build. Anyone who tells you differently has NO clue what they are talking about.

The ammeter would have to have 3 or more terminals on it to be doing this "balancing of currents" thing you're writing about.


Dude, the ammeter will NOT read a discharge when the fans and pump are getting their power from the battery instead of the alternator. So, if you get a slight discharge at idle then you MUST add around 20A to that discharge current to know the true discharge current.

Measure the fan current and pump current. Add the 2 measurements together. You're not charging the battery until the ammeter is reading HIGHER than that current. If the battery truly is charging with the fan and pump running while the meter is reading 2-3A then the meter is not working correctly at all.

jersey68l36

With the engine at curb idle, heater fan blower on high, all head lights on, take a voltmeter and check out the voltage across the battery terminals. reading less than 13v which it most likely will be with the stock alternator, then as mentioned in this thread, a higher amp alternator is needed.

DUB

You are aware of what is going on and have a game plan if future electrical improvements/upgrades are installed.

Like I wrote..I have to have it work on the maximum draw on the system as possible so I do not have to have customer call and wonder why 'this or that' is correct.

This reminds me of the customers with C4's that would bring me in the smaller pulleys that were offered/sold to put on their engine. And when the engine was running at idle...it was not charging well at all...but when you increased the RPM's...it did fine. Many of those customers who paid for those pulleys had me take them off and put the original ones back on.

DUB

ronarndt

Lionel- thanks for your comments, but when someone's online posts become insulting I no longer participate. I had a metrology department under my supervision at Salk Institute and Greer Laboratories whose sole function was calibrating laboratory equipment, instruments and gauges. The feedback I got from one of my former technicians supports my opinion the smaller gauge wire affected the reading on the ammeter. Plus......installing the correct size wire has the gauge working as it did when I got the car three years ago. Anyway, thanks for your help. RA