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Old 08-10-2005, 04:54 AM
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Melted Amp Meter gauge

Well I recently took my Nova for a joy ride (can't go far due to transmission problems, maybe 15 minutes.) But anyway, I shut the car off and when I went to go look in the interior once again the gauge had melted, literally. The metal piece where the positive and negative sides meet had literally melted off the back of the gauge. I realize that there is probably a short of some kind somewhere, but I was just wondering if this may have happened to someone else, where I might have an idea to start looking. I am sorry for the lack of information, but that is basically, LITERALLY what happened.

I know it is a longshot, but thanks in advance for any info you guys can shed on the situation.

Thanks for everyones time,

Rob
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Old 08-10-2005, 05:13 AM
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Read this then replace the ammeter with a voltmeter
http://www.madelectrical.com/electri...p-gauges.shtml
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Old 08-10-2005, 07:47 AM
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amp gauge

right off I am guessing that the gauge is the problem. start there. A short in the instrument it self cause the melt down
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Old 08-10-2005, 07:48 AM
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Is this a factory guage or aftermarket?

Restoration or hotrod??

Rich
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Old 08-10-2005, 03:01 PM
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Gauge

Doc here,

Makes NO Difference..

Anyway, sounds like the gauge Shunt was over taxed..you may have shorted the LOAD side of the gauge to the instrument panel by accident.

In a proper Working system as advertised, You have Fuse links protecting the Circuits they draw from, None of those apparently Blew..so the rest of the system SHOULD be fine...However, when you do correct the AMP gauge, you may just want to have the alternator tested for output.

Doc
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Old 08-10-2005, 04:59 PM
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Quote:
Originally Posted by docvette
Doc here

Makes NO Difference..
Is does make a difference but I guess you are entitled to your opinion.
Rob,

There was a reason I asked if it's a restoration and if you have original guages. If so, I am sure you would want to replace the guage to maintain originality and find out what the cause of the problem was.

If its a modified car, street machine, etc. I would recommend you replace the ammeter with a volt meter and be done with this old (COMMON problem) safety hazard. I have worked on dozens and dozens of cars that have burnt looms (and even fires) because of ammeter failures.

Most aftermarket guages are worse than originals. Even a lose connection on the back of the meter can cause high current which in turn gets hot and quickly melts the insulators where the stud comes though case on the meter. Next thing you know you have a short and before you know it you have glowing high current wires everywhere. This melts other wires, plastic and anything that it come in contact with.

So yes it does matter... If given the choice when spending your money on a new meter, be safe and get a voltmeter.

Rich
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Old 08-10-2005, 05:21 PM
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Makes No Difference...

Doc here,

It makes NO difference BECAUSE aftermarket or original...It went from working to potential fire hazard...It's broke and needs attention.

The Ammeter should have been surrounded by fuse links in the B+ , circuit why those didn't open is anybody's guess...You need to Check why those didn't open, or if they are even there..

However somewhere at or near the gauge you have suffered a massive current draw through the gauge shunt..It will heat and melt plastic and contribute to further shorting, could be loose connections, could be wire just hitting the metallic instrument panel.

Ammeter or Voltmeter is just a matter of preference, if you learn to read both, you can get the same results from either..I have Voltmeters in all the Vettes and they are quite accurate.

Doc
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Old 08-10-2005, 05:36 PM
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Doc,

Well you basically just argued and then repeated what I said.

Yes as YOU stated voltmeters are accurate (as in your vettes). Remember that was the direction I was steering him if he was NOT trying to maintain originalilty.

Because voltmeters are accurate and they are MUCH safer, I would not lose sleep over trying to figure out why it went bad and move towards a better system. Ammeters are known to be a problem and less safe than a voltmeter. No one will argue that.

So once again whether he is going for original or aftermarket it DOES matter. If its a hot rod and you are buying a new guage, buy a voltmeter.

Rob,

I was not kidding. I worked for a custom rod shop/restoration center for around 10 years doing nothing but building custom looms and wiring on streed rods as well as original electrical repairs. I have seen dozens and dozens of burnt cars from ammeter problems.

So the choice still lies in your hands. Original or Hotrod? It does matter.

Rich
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Old 08-10-2005, 06:38 PM
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Volt/Amp meters

Doc here,

No I think not...not completely anyway...yes in fact the voltmeter is a good alternative system and far superior safety~Wise than a high current amp system..I think we agree on that..100%

However...EVEN if he abandons The AMP gauge..He needs to address the why and wherefore of the failure..OTHERWISE he's just whistling past the graveyard. You just can't clip out the gauge and say "It's ALL Good.." That circuit needs to be addressed.

Damage , even sidebar Damage can exist and rear it's ugly head further down the road..

Once you do that, and Clear and repair the reason for the failure, the choice then is again yours..Amp meter or voltmeter..Since the failure is now repaired.

In My 37 Years of wrenching on Vettes as well as other's , I too have seen many failures and fires where the root cause was an errant Amp meter..but going a step further , I have always found (In 90% ) of those cases that they were installed wrong by the owner, or others..Or Inferior Parts used..

Think about it..Amp Gauges have been around since The Model A, and Some of those are original and STILL work..Many production Vehicles came out with them and still function fine today...With the Brilliant exception of some Dodge/Plymouth that were "Just Wrong"...

Don't get me wrong here, I DO NOT like Amp gauges...never have..and will always go for an voltmeter given a choice..

However Where (at least for appearances) You can replace that stock Amp gauge for an Exact copy of the original, with one exception..It's inductive not a direct pick up.

Sure, It costs more, sure it may have to be custom ordered, and you have to retain the stock gauge and operating circuit capped off, for when you go to sell/Show the vehicle..but it's a small price to pay...and 99 folks out of 100 won't know the difference.

So yes we agree on a lot but disagree on a lot also...but that what makes this medium a good one for all..you can see both sides.

Doc
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Old 08-10-2005, 06:52 PM
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Doc,

I agree 100%. A failure in this manner may have done more damage. As a matter of fact it was likely as I am sure you will agree.

I "kinda" like ammeters. Its a nostalgic sickness but we both agree on why not to recommend them. So I dont

I just wanted to know what kind of car we are dealing with as far as original, etc. From there I would have chimed in on my thoughts on the path to take. All just my opinion of course.

Best wishes,

Rich
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Old 01-25-2010, 07:02 PM
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Minor correction - Ohm's Law

McCabe seem to have made a small mistake, so I just want to clarify one minor point.

When you properly connect a high-current wire, you have very near zero ohms resistance. When you improperly make such a connection, you have slightly MORE resistance (not less). Ohm's law states that an increase in resistance causes a decrease in current, in this case a very small increase in resistance, and an equally small decrease in current.

So the statement "Even a lose connection on the back of the meter can cause high current which in turn gets hot and quickly melts the insulators where the stud comes though case on the meter." contains a minor error. The lose connection does not increase the current. It actually decreases the current. But since you now have about a 1/2 ohm resistor (or larger) at the connection site, you now have a Voltage Drop across the connection. This resistance causes the generation of huge amounts of heat, since your small resistance at the connection is seeing the full CURRENT of your load. The heat from this 'resistor' (the bad connection) melts everything around it.

PS - All mechanical amp meters are inductive in nature, and all of them must run the entire load (current) through some part of the meter. Most electronic amp meters use voltage to approximate the current, but still use a low resistance, high current, shunt, and are therefore no less dangerous. Use a Hall Effect electronic DC amp meter with a remote sensor (attached to the OUTSIDE of the insulated battery cable) to eliminate all potential hazards and minimize the impact of the meter on the system (and then you do not have to run a 50 amp cable from the battery to the cabin, and back to the engine compartment).

A note about Voltmeters. While they are safer, and they do convey a lot of information, they do not convey the amount of current going in/out the battery when it is charging/discharging, so undesirable battery conditions and charging system conditions can be more difficult or impossible to detect. However, combining both Voltage and Current meters gives enough information to track battery and charging system conditions extremely well.

Quote:
Originally Posted by rrmccabe
Is does make a difference but I guess you are entitled to your opinion.
Rob,

There was a reason I asked if it's a restoration and if you have original guages. If so, I am sure you would want to replace the guage to maintain originality and find out what the cause of the problem was.

If its a modified car, street machine, etc. I would recommend you replace the ammeter with a volt meter and be done with this old (COMMON problem) safety hazard. I have worked on dozens and dozens of cars that have burnt looms (and even fires) because of ammeter failures.

Most aftermarket guages are worse than originals. Even a lose connection on the back of the meter can cause high current which in turn gets hot and quickly melts the insulators where the stud comes though case on the meter. Next thing you know you have a short and before you know it you have glowing high current wires everywhere. This melts other wires, plastic and anything that it come in contact with.

So yes it does matter... If given the choice when spending your money on a new meter, be safe and get a voltmeter.

Rich
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