Hey all, I just installed a new gauge cluster in my 1972 duster and when the car is running smoke comes from the alternator gauge pegs. I’m not sure why this would be, I’m wondering if anyone had a similar issue or knows the fix? Thanks
Alternator gauge is smoking
- Thread starter 67cudaGuy
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67Dart273
Well-Known Member
The ammeter circuit is a major circuit, and the ammeter is in SERIES with all loads in the car except the starter. It is therefore, a "heavy" circuit and IT IS NOT FUSED except for the main fuse link, which is poor protection
It could smoke at any time as it is always "live." You are saying "only when running" which implies probly a charging problem, as the alternator increases current
Make CERTAIN the ammeter is assembled correctly and that the studs/ nuts are tight. If so, check charging/ running voltage to make certain the system is not grossly over-charging, perhaps a wiring error, something wrong with the regulator or the alternator
72 has the "isolated field," often INcorrectly called "dual field." IT is common for one of the alternator field terminals to short to ground, and if the blue wire (switched 12V) is hooked to the opposite alternator field terminal, the alternator will charge "full steam."
I WOULD NOT LEAVE THE VEHICLE with the battery connected until you get this problem "found"
It could smoke at any time as it is always "live." You are saying "only when running" which implies probly a charging problem, as the alternator increases current
Make CERTAIN the ammeter is assembled correctly and that the studs/ nuts are tight. If so, check charging/ running voltage to make certain the system is not grossly over-charging, perhaps a wiring error, something wrong with the regulator or the alternator
72 has the "isolated field," often INcorrectly called "dual field." IT is common for one of the alternator field terminals to short to ground, and if the blue wire (switched 12V) is hooked to the opposite alternator field terminal, the alternator will charge "full steam."
I WOULD NOT LEAVE THE VEHICLE with the battery connected until you get this problem "found"
Ironracer
Gearhead
Op, 67Dart273, is one of the Top Notch Electronics experts here! You are in Great shape!
IMHO if the alt gauge is smoking you need to pull the gauge out and have a good look at it
I recently purchased 2 67 - 69 dart clusters, I was looking for good temp fuel gauges. BOTH had trashed alt gauges. One the posts were completely loose in the gauge, so it would create a high resistance under load and got hot enough to melt the pot metal housing.
The other had the posts twisted to the point the metal it is attached to was touching other metal parts. That would have made a direct short.
I can provide photos if need be
I recently purchased 2 67 - 69 dart clusters, I was looking for good temp fuel gauges. BOTH had trashed alt gauges. One the posts were completely loose in the gauge, so it would create a high resistance under load and got hot enough to melt the pot metal housing.
The other had the posts twisted to the point the metal it is attached to was touching other metal parts. That would have made a direct short.
I can provide photos if need be
The alternator gauge ASSUMING in 72 it is the same as 67. ( I seem to recall there was a change some where along the way)
It is in series with the output of the alternator to the battery, meaning all the current that goes into the battery from the alternator runs through the gauge.
67Dart273
Well-Known Member
Ammeter "alternator gauge" has nothing to do with the voltage limiter. They are a high current ammeter with the main wiring going directly to them.
As already stated, the gauge must come out to repair the damage and to inspect it. In addition to the nuts being loose and or corroded, check the studs. The studs are pressed into a piece of thin brass which is part of the ammeter itself. Overtorquing the nut one time will cause a poor connection of the stud.
Remove the cluster. Remove the wires from the ammeter. Get a small wire brush and clean around the terminals of the ammeter very good. Also clean the attaching nuts and the eyelets on the end of the wires that attach to the ammeter. All of that needs to be CLEAN as possible. Sometimes, dust, dirt and even corrosion from the terminals being loose will make a poor connection and add resistance which will add heat, especially when the alternator is charging. Clean, clean, CLEAN! And TIGHT! But do not over torque.
Could that gage and wire be to small if someone was to put a higher output Alternator on the Engine.?
It looks good in that there are no signs of heat and its clean and shiny. Also the insulators look OK.
That doesn't mean it is good. You have to tell us if the threaded studs are secure in the metal plate.
You can measure the resistance from one stud to the other but unless its really in bad condition, it will show zero resistance.(illustrated here)
Look at the rest of the connections, if either ammeter ring terminal touched ground anywhere, there should be signs of heat damage.
That doesn't mean it is good. You have to tell us if the threaded studs are secure in the metal plate.
You can measure the resistance from one stud to the other but unless its really in bad condition, it will show zero resistance.(illustrated here)
Look at the rest of the connections, if either ammeter ring terminal touched ground anywhere, there should be signs of heat damage.
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This is a the basic scheme of a standard 1972 Valiant.
Using your finger follow the line from the battery positive terminal.
Everything connected to the battery positive is hot.
Color of the wire does not matter. Up to the switches, everything connected to the battery is at battery voltage.
The ammeter shows zero because no electrons are moving. They're just very excited and ready to move when a path to ground becomes available.
Voltage should be the same everywhere that is connected to battery positive. You can measure it at the alternator 'Batt' terminal or at the fusebox, it doesn't matter.
If you think of current like a river of electrons flowing, with all the switches off, the river is blocked. Pressure behind the blockage is the same everywhere. That pressure is the voltage.
The ammeter is not a switch, up through '75, its just a U shaped metal plate that creates a small magnetic field when the electrons are moving. The magnetic field deflects the needle.
Using your finger follow the line from the battery positive terminal.
Everything connected to the battery positive is hot.
Color of the wire does not matter. Up to the switches, everything connected to the battery is at battery voltage.
The ammeter shows zero because no electrons are moving. They're just very excited and ready to move when a path to ground becomes available.
Voltage should be the same everywhere that is connected to battery positive. You can measure it at the alternator 'Batt' terminal or at the fusebox, it doesn't matter.
If you think of current like a river of electrons flowing, with all the switches off, the river is blocked. Pressure behind the blockage is the same everywhere. That pressure is the voltage.
The ammeter is not a switch, up through '75, its just a U shaped metal plate that creates a small magnetic field when the electrons are moving. The magnetic field deflects the needle.
Key off:
A ground short anywhere after the ammeter should cause the needle to peg discharge. If there is short on the battery side it will not show on the meter.
Another way to put enough current through to smoke wires is with the engine running and a low a battery.
Here's what happened to someone's ammeter wires when they let the engine run for 20 minutes with the ammeter pegged to charge.
A ground short anywhere after the ammeter should cause the needle to peg discharge. If there is short on the battery side it will not show on the meter.
Could be a short as 67Dart273 described above
Another way to put enough current through to smoke wires is with the engine running and a low a battery.
Here's what happened to someone's ammeter wires when they let the engine run for 20 minutes with the ammeter pegged to charge.
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67Dart273
Well-Known Member
I don't see anything obvious at the gauge itself. Mattox brings up some good points. "Something" causing excessive current in that circuit, either a load/ short, or very high charging current AND OR a loose connection
This is, really all the fuss about upgrading, rebuilding, or eliminating the ammeter circuit. The main trouble areas are...........ANY terminal in the circuit, from out in the engine bay, through the firewall, at the ammeter, and back again, or looseness at the ammeter terminals.
One thing you might do is to rig it up (you don't need the cluster) and bolt the ammeter wires together, tape them up temporarily, run the car, check charging voltage and LOOK for hot wires, all the way from the fuse link, through the bulkhead, include the two ammeter terminals, and back out on the "big black," back out the firewall to the battery
I WOULD ALSO check the "welded splice." Go to the black ammeter wire terminal. Unwrap enough of the harness (a few inches) and follow the big black down the harness, until you get to a big splice. Unwrap and inspect that splice. They are welded but THEY HAVE AND DO fail occasionally.
This is, really all the fuss about upgrading, rebuilding, or eliminating the ammeter circuit. The main trouble areas are...........ANY terminal in the circuit, from out in the engine bay, through the firewall, at the ammeter, and back again, or looseness at the ammeter terminals.
One thing you might do is to rig it up (you don't need the cluster) and bolt the ammeter wires together, tape them up temporarily, run the car, check charging voltage and LOOK for hot wires, all the way from the fuse link, through the bulkhead, include the two ammeter terminals, and back out on the "big black," back out the firewall to the battery
I WOULD ALSO check the "welded splice." Go to the black ammeter wire terminal. Unwrap enough of the harness (a few inches) and follow the big black down the harness, until you get to a big splice. Unwrap and inspect that splice. They are welded but THEY HAVE AND DO fail occasionally.
As promised...
(I did not have photos of the bent post support one )
Top post is wobbly loose.
Bottom post was tightened so much it deformed the metal strap it is attached to.
There are two housings. The one with the melted lense and deformed (melted I suspect) are from the alt meter in the photos.
The last housing had the twisted alt meter post.
(I did not have photos of the bent post support one )
Top post is wobbly loose.
Bottom post was tightened so much it deformed the metal strap it is attached to.
There are two housings. The one with the melted lense and deformed (melted I suspect) are from the alt meter in the photos.
The last housing had the twisted alt meter post.
I agree it looks amazing, out of 3 clusters I bought only one alt gauge looked that good.
Are the posts firm to the metal they are attached to?
Enjoying this tec support, learning as well.
Thanks to all the members chiming in
Thanks to all the members chiming in
ESP47
Well-Known Member
Could also take a HF voltmeter, put it on amps and connect it in series where the ammeter would go and see what kind of amps you're pulling. If the problem goes away it's either something internal to the factory gauge or a connection issue at the back of the gauge itself. The pics of the gauge look great but that obviously doesn't tell the whole story.
If you use a HF meter to do the reading, just make sure that you connect and tape the leads on it to the vehicles wire leads very securely so they don't slip or short out on anything. Sometimes reading amps can be a pain depending on where it needs to be done at but you've already done the difficult part by removing the gauge.
If you use a HF meter to do the reading, just make sure that you connect and tape the leads on it to the vehicles wire leads very securely so they don't slip or short out on anything. Sometimes reading amps can be a pain depending on where it needs to be done at but you've already done the difficult part by removing the gauge.
I see some debris from dirt and maybe corrosion on the connections.
Ragtop Bob
New Member
All Amp meters have a shunt (a bypass resistor) across the meter to carry the high current around the meter movement. It sounds like the meter shunt is damaged. The shunt may be internal to the meter. Can you try using the old meter to see if the problem clears up?
joemish
Member
pegs grounding together somewhere
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