Alternator gauge question

-
OwdKasd

OwdKasd

Well-Known Member
Joined
Jul 17, 2011
Messages
1,563
Reaction score
53
Location
Mount Airy, NC
While cruising with lights off and no significant load on my charging system, My alt. gauge is reading about 35 amps or so(Near Full). Is this normal? I am used to the gauge coming back down to the middle position once the battery charges back up after a start-up.
I know it's highly recommended to bypass these but I am waiting until I get everything working correctly.
I am having some other electrical issues(dash lights etc...) and want to see if the Alternator gauge/circuit may be related.
 
No, not normal -- it should ride at or near the centre of the gauge under normal circumstances. Check for a faulty or poorly-grounded voltage regulator, or a dead cell in the battery (is your cranking speed noticeably slower than normal? What's the voltage across the battery with the engine off after you drain off the surface charge by running the headlights for 60 seconds?).
 
Ignore the old man behind the curtain

wizard-of-oz-man-behind-the-curtain11.jpg


There are about 4 things that can cause this

1 Make sure the battery is charged, remove it, and find someone who has and knows how to use a "carbon pile" battery tester like this:

atm-sb5-2.gif


If you have a battery "with caps" consider buying and learning how to use ahydrometer. Get one that is "temperature corrected, IE "has a thermometer"

2 Make some tests. Hook one probe of your voltmeter to the battery positive POST, the other probe to switched ignition, IE ignition 'run.' Turn the key to "run" with engine off. You are measuring voltage drop from the battery through the harness, bulkhead, and switch, and are HOPING for a very low reading. More than .2--.3V (three TENTHS of a volt) is too much, and means a bad connection somewhere. Your top suspects are the bulkhead connector, the igntion switch connector and switch, and in rare cases, the ammeter circuit

3 Next, Start the engine, get the battery "as normal as possible" with the engine running at "low to medium" cruise RPM. IF THE VOLTAGE was significant in the above tests, "rig" a jumper from the battery (starter relay stud) to "igntion run" so that the regulator gets actual battery voltage.

Measure charging voltage, and see if this jumper brings charging voltage down to 13.8--14.2 or so

4 Next, with engine running, stick one probe of your meter directly onto the battery NEG post, and the other directly onto the regulator mounting flange. Be sure to "stab" through any paint, chrome, etc

AGAIN, you are hoping for a low reading, less than .2--.3V MORE than that figure means a poor ground between the battery, block, body, and regulator.

On my car, I used a 1 ft "starter cable" (no4 "ring to ring") from a rear head bolt hole to the master cylinder mount.

5 If all the above checks OK and the charging voltage is still high, replace the regulator
 
Battery is at 12.7 volts after sitting overnight. Concerning the Charging system and battery, Everything is functioning fine other than the gauge reading high. I guess it's possible that gauge is reading right. Headlights are nice and bright while running.

The problem here is that I have several other electrical issues. No dash lites. Intermittent ignition switch problems requiring me to jump the Starter solenoid. The weird thing is that when it will start with they key, then the alt gauge reads high. Like somehow the Starter solenoid/alt gauge/ign. switch are related. I'm pretty sure the Dash light problem is a bad headlight Switch.
 
Maybe something became mis--wired

IS the gauge centered with everything off?

Try "with engine off" turn on some loads, heater, radio, turn signals, anything you can. Does the meter deflect discharge for each, appropriately?

Do you have anything added, like electric fans, big stereo amp?

You say "everything is functioning fine." What does that mean? Have you checked charging voltage at the battery? What does it read?

Here's what I'm thinking?

If you changed some wiring, or added some loads, (like electric fans) and hooked them to a battery source under the hood, TWO things will happen

1 The new load, connected to the battery, will NOT show discharge through the ammeter with the engine off

2 This will ALSO skew the gauge reading. Let's say you had a big fan turn on, ON AN OTHERWISE normally operating system, with the ammeter CENTERED as per "normal."

IF the load is connected on the "wrong side" of the ammeter, and the fan turns on, it will now SHOW A CHARGE by the same amount of amps which the load draws.
 
67Dart273 said:
Maybe something became mis--wired

IS the gauge centered with everything off?

Try "with engine off" turn on some loads, heater, radio, turn signals, anything you can. Does the meter deflect discharge for each, appropriately?

Do you have anything added, like electric fans, big stereo amp?

You say "everything is functioning fine." What does that mean? Have you checked charging voltage at the battery? What does it read?

Here's what I'm thinking?

If you changed some wiring, or added some loads, (like electric fans) and hooked them to a battery source under the hood, TWO things will happen

1 The new load, connected to the battery, will NOT show discharge through the ammeter with the engine off

2 This will ALSO skew the gauge reading. Let's say you had a big fan turn on, ON AN OTHERWISE normally operating system, with the ammeter CENTERED as per "normal."

IF the load is connected on the "wrong side" of the ammeter, and the fan turns on, it will now SHOW A CHARGE by the same amount of amps which the load draws.
Click to expand...
It's charging 12.37 parked & climbs up to 16 volts at cruise. Battery holds charge. Car starts fine other than having to jump solenoid. Other than Autometer Temp & oil pressure gauge, there's no extra Electrical stuff, no radio, fans etc. Definitely got a charging system problem
 
Well the plot deepens


The ammeter DOES drop to center if the car is shut off?
 
67Dart273 said:
Well the plot deepens


The ammeter DOES drop to center if the car is shut off?
Click to expand...
Yes sir! It does drop to center with engine off. One other thing with the Dash lights, The Instrument fuse now has no power on either side. I'm thinking there's a common wire to all these items or a ground problem. Thanks for the help. My brain is spinning right now.
 
Instrument lamp fuse gets its power from the headlight switch. Pull the switch to at least the park lamp position and check that fuse again.
 
RedFish said:
Instrument lamp fuse gets its power from the headlight switch. Pull the switch to at least the park lamp position and check that fuse again.
Click to expand...
Thanks RedFish, I tried that with no luck. The weird thing is that at one point I had power on both sides of that fuse when Key was on but light switch was off. I think the PO has done some creative wiring and it is failing. Thanks everyone else for all the tips & Ideas. I'll be in the Garage for a while just trying to figure it out and cleaning up the bulk head wire connections.
 
Voltages say your battery and charging system are fine. You say when you're able to start the car with the key the ammeter reads high—do I understand you correctly that if you don't use the key to start the car, the ammeter reads normally? If so, your symptoms suggest an internally faulty ignition switch. Don't know if you've ever tried it, but if you're driving down the road (car in gear, engine running, duh) and you turn the key to the "Start" position, the ammeter will peg high. Try another experiment: the next time the engine's running and the ammeter reads high, rev the engine up high enough to allow you turn the key off and then back on without the engine stopping. Try it several times in a row if necessary and see if you're able to get the ammeter to come down to normal reading. If so, replace the ignition switch.
 
Yep. What I do is push the car out of the garage and the try to start it with the key. Sometimes it works but usually I have to get out and jump the solenoid(I use a nickel). This last time it started with the key and I took a little cruise and noticed the Alt gauge almost pegged at full. There are several other things not working. I'll list them and maybe some one will spot a common item that could cause all/most of the problems:

Problem list:
No dash lites.
Alt gauge read almost full at cruise lights off.
Voltage goes up to 16v at cruise.
Intermittent no start with key(Need to jump solenoid)
Front marker lites very very Dim(need to clean corrosion from sockets


slantsixdan said:
Voltages say your battery and charging system are fine. You say when you're able to start the car with the key the ammeter reads high—do I understand you correctly that if you don't use the key to start the car, the ammeter reads normally? If so, your symptoms suggest an internally faulty ignition switch. Don't know if you've ever tried it, but if you're driving down the road (car in gear, engine running, duh) and you turn the key to the "Start" position, the ammeter will peg high. Try another experiment: the next time the engine's running and the ammeter reads high, rev the engine up high enough to allow you turn the key off and then back on without the engine stopping. Try it several times in a row if necessary and see if you're able to get the ammeter to come down to normal reading. If so, replace the ignition switch.
Click to expand...
 
I rigged up my Tektronix meter and took a test drive.It's charging 12.37 parked & climbs up to 16 volts at cruise. This is consistent with the Amp(Alternator) Gauge. Battery holds charge. Car starts fine other than having to jump solenoid. Other than Autometer Temp & oil pressure gauge, there's no extra Electrical stuff, no radio, fans etc. Definitely got a charging system problem . Now I just have to diagnose the Voltage Regulator and wiring to it.
 
OwdKasd said:
I am going to start by doing exactly what you did as far as the wiring Mod's. Did you have trouble Identifying which wires to re-route/Splice etc..??
Click to expand...

none whatsoever. first i took out the cluster and soldered and wrapped the ammeter gauge wires together. then i followed the red and black wires inside the car to the bulkhead , cut the wires , and connected each of them to my new wires and ran them through the firewall to the starter relay. i wasnt worried about it looking factory, so i just re-routed them through an existing hole in the firewall. oriellys has the proper wire size and fusable links for like 5 bucks. make sure the two wires that come out of the bulkhead are elimated from any power source. it was really easy and did not take long. getting the cluster out was the most time consuming
 
Let's step back a square or two. Can you measure the dark blue "ignition run" wire, what you want to do is check for harness voltage drop

Turn the key to "run" engine off. Hook one probe of your meter to battery positive, the other probe to an "ignition run" connection, either at the ballast, or the blue alternator field wire.

You are hoping for a VERY low reading, below .3V (three tenths of a volt) If more, you have a drop somewhere in the ignition supply harness, either the bulkhead connector, the ignition switch connector or the switch, or the ammeter circuit.

What this voltage drop does, is the regulator "reads" this voltage, and if it's low, the regulator jacks the system voltage up until that line comes up to the regulator setpoint. If the regulator is properly operating at around 14V, and you have (as my 67 Dart) let's say a 1 volt drop, the regulator ADDS that to it's setpoint, so the battery sees 15V

I've got lost, here, did you check voltage for regulator ground?

With system charging and running, stick one probe on the battery NEG post, and the other on the regulator case. AGAIN, as above you want a low reading, the lower the better, Over .2V or so means a poor ground between regulator, body, block, and battery.

As usual, Big Dan has not bothered to explain himself. I suspect he is intimating at this very problem, IE a bad ignition switch
 
Ditto 67Dart273. You need to compare two dV (delta voltage) signals. dV across the battery, which you already measured as 16 V with engine revving (too high). You need to measure dV that Vreg senses which is from its case to its IGN wire. Our guess is that Vreg sees a much lower dV, due to drops in the wiring and connectors. It probably sees ~14 V (what it wants the battery to be).

More commonly wiring is a problem, not the Vreg. However, if you have the old mechanical Vreg (large black rectangular box w/ wire resistors on bottom), it could be quirky (pitted contacts, moth stuck in contacts). If so, change to an electronic Vreg in the future. All your problems are likely due to bad contacts, especially the firewall bulkhead connector and maybe the round dash cluster connector.
 
Test 1 at blue wire. 9.15 volts w/key in run. 12.67 w/key off. Need to push car out of garage and start it for next test but I thought I'd post this info 1st.

67Dart273 said:
Let's step back a square or two. Can you measure the dark blue "ignition run" wire, what you want to do is check for harness voltage drop

Turn the key to "run" engine off. Hook one probe of your meter to battery positive, the other probe to an "ignition run" connection, either at the ballast, or the blue alternator field wire.

You are hoping for a VERY low reading, below .3V (three tenths of a volt) If more, you have a drop somewhere in the ignition supply harness, either the bulkhead connector, the ignition switch connector or the switch, or the ammeter circuit.

What this voltage drop does, is the regulator "reads" this voltage, and if it's low, the regulator jacks the system voltage up until that line comes up to the regulator setpoint. If the regulator is properly operating at around 14V, and you have (as my 67 Dart) let's say a 1 volt drop, the regulator ADDS that to it's setpoint, so the battery sees 15V

I've got lost, here, did you check voltage for regulator ground?

With system charging and running, stick one probe on the battery NEG post, and the other on the regulator case. AGAIN, as above you want a low reading, the lower the better, Over .2V or so means a poor ground between regulator, body, block, and battery.

As usual, Big Dan has not bothered to explain himself. I suspect he is intimating at this very problem, IE a bad ignition switch
Click to expand...
 
You have found the area of the problem.

One "work around is to pull ALL load off the dark blue, that is cut it before it gets to the bulkhead resistor, and use it to fire a good quality relay, then use the relay to supply ignition and regulator loads

Otherwise, you need to dig in and see where you've "lost" it

Again, the top suspects are the bulkhead connector itself (At least two, the main battery feed goin "in" and the dark blue coming back "out"), the ignition switch connector or the switch itself.
 
Okay thanks, Do you think doing the Madelectric Mod would fix this wiring issue or is it seperate? I'm specifically talking about the Mod at this link.
http://www.madelectrical.com/electricaltech/amp-gauges2.shtml

67Dart273 said:
You have found the area of the problem.

One "work around is to pull ALL load off the dark blue, that is cut it before it gets to the bulkhead resistor, and use it to fire a good quality relay, then use the relay to supply ignition and regulator loads

Otherwise, you need to dig in and see where you've "lost" it

Again, the top suspects are the bulkhead connector itself (At least two, the main battery feed goin "in" and the dark blue coming back "out"), the ignition switch connector or the switch itself.
Click to expand...
 
Sorry about this but I think I messed up the test. Was I supposed to pull the blue field wire connector off of the Alternator or leave it plugged in. If I pull it off, I get 12.47 volt.
 
OwdKasd said:
While cruising with lights off and no significant load on my charging system, My alt. gauge is reading about 35 amps or so(Near Full). Is this normal? I am used to the gauge coming back down to the middle position once the battery charges back up after a start-up.
I know it's highly recommended to bypass these but I am waiting until I get everything working correctly.d
I am having some other electrical issues(dash lights etc...) and want to see if the Alternator gauge/circuit may be related.
Click to expand...
This is not normal and it could be a dangerous situation as you could be over charging your battery. I've seen batteries explode from this. I suspect a bad regulator or a bad ground at the regulator.
 
The MAD approach should fix most of the problems, but a simpler approach would probably get you there. Run an 8 awg wire directly from ALT big stud to BATT+. Run it across your timing cover and put it in sheath (split loom or smooth PVC). You can leave your ammeter connected, but it won't read much since now bypassed (unless you follow my post w/ the bypass diodes).

Remove the 2 bulkhead connectors for lights and engine (can leave the wiper plug as is) and remove each male terminal (squeeze long way w/ needle-nose & wiggle) and clean each w/ sandpaper (one at a time, don't mix them up). Clean the female terminals (cabin side) as best you can with a small file, then spray with contact cleaner (hardware store). Squeeze silicone dielectric grease in the female terminals and reconnect. For anything that is still erratic, remove the connectors in the engine and/or cabin and do the same.

For broken (or almost broke) wires, solder and cover w/ heat shrink. Do the same for any wires you find with the clunky butt crimp "repairs" that every clueless mechanic uses.
 
OwdKasd said:
Okay thanks, Do you think doing the Madelectric Mod would fix this wiring issue or is it seperate? I'm specifically talking about the Mod at this link.
http://www.madelectrical.com/electricaltech/amp-gauges2.shtml
Click to expand...

these are for reference for you if/when you get to this point. keep on keepin on with what you guys got going on.


here are a couple pics. now, i clipped the old wire leading to the alt stud, wrapped it up with tape and left it in the harness. i ran a brand new wire to a fusible link and to the relay.

the amp gauge wires go together. the thick red wire that goes to the bulkhead, was clipped, and ran to the relay with a fusible link.

the thick black wire that comes from the harness to the bulkhead, (inside the car) was cut and a new wire ran to the starter relay. i tied this one in with red wire at the relay, going onto one fusible link to the relay.

the black wire, that goes through the bulkhead, is a fusible link on the engine bay side. i cut that wire on the engine bay side, and wrapped it up in tape, left it in the harness. the old red wire that was connected to the starter relay/ through the bulkhead/to the gauge was also clipped and wrapped and left alone.
this is how it looks as outlined in the diagram in the mad link you posted above
 

Attachments

  • start.jpg
    66.7 KB · Views: 445
  • start1.jpg
    79.9 KB · Views: 424
  • start2.jpg
    100.2 KB · Views: 444
You must log in or register to reply here.
-

Back
Top