Is the factory Amp meter a fire hazard? (discuss)

[PaceFever79]

I've read that any Amp meter / harness is a fire hazard.

Would it be prudent to remove this circuit before something happens?

If so, what would be the best way to go about doing it?

[IDMooseMan]

I'm not sure if it is any more or less of a fire hazard than any other electrical instrument. Personally, I prefer a "Volt" gauge and am considering installing one in place of the OEM "Amp" gauge, but that is due to person preference, not due to a perceived fire hazard. I would think that any electrical component could potentially become a fire hazard if the wiring is damaged in such a way that an electrical short could happen.

Are you referring to a specific article you read regarding a possible fire hazard associated with the amp gauge?

[PaceFever79]

Do a google there are many references to them being fire prone (not just on our cars). The problem is the charging current flows from the alternator through the Ammeter then back to the battery.

[87gtVIC]

Pretty sure these meters operate with a shunt. Gives just a sample of what is going on in the charging system. You do not have the entire charging circuit entering the dash and exiting back into the engine compartment.

[PaceFever79]

I was just thinking since it is a useless gauge, and a fire hazard, why keep the circuit at all?

[PaceFever79]

Pretty sure these meters operate with a shunt. Gives just a sample of what is going on in the charging system. You do not have the entire charging circuit entering the dash and exiting back into the engine compartment.

That is why I posted the question,

I'm not sure how much of the charging current flows through it.

[IDMooseMan]

Do a google there are many references to them being fire prone (not just on our cars). The problem is the charging current flows from the alternator through the Ammeter then back to the battery.

I did and found a LOT of fire hazard references. I think I'll add "Convert to voltmeter" to my project plan.

Thanks for posting this thought-provoking question.

[Dean_T]

I don't recall the Fox Mustangs having fire issues due to the shunt style ammeter wiring which has much less current going through it than the main power feeds to the fuse box.



The '84's ammeter wiring - yellow-green and red-orange wires with a "hunk" of large gauge Yellow wire inbetween - not the best picture but you can see it wasn't meant to carry the full current feeding power to the car. It has a smaller amount of current flowing through it - unlike the ammeter in my '79 Dodge truck which does carry the full current load feeding the dash wiring and under hood circuit. A really dumb design and there were many instances of the ammeter going up in smoke. It's a known problem of the '75-'80 Dodge trucks which may owners have installed by pass wiring to remove the ammeter and the connector at the firewall from the wiring circuit to prevent the fire hazard.

Now mid '70's to '80's Ford ignition switches, including the one used in the Fox chassis vehicles, have had burned cars and garages to the ground...

[jessesandy]

Here are two articles about the Ford ammeters. The history of fires and the "shunt" fix. Does it even do anything ? And the best part is reference to a Ford service bulletin to test the ammeter "... if you can see ANY movement of the needle, its working..." !?! (insert smilely face)

http://automotivemileposts.com/garage/v2n7.html
http://www.fordification.com/tech/ammeter.htm

Thanks, Todd H.

[Dean_T]

Rest assured, Ford learn a lot since 1972. All '79-'86 Mustangs have the lower amperage shunt style Ammeter (Didn't I post this already?). Dodge still haven't learned that lesson with their '75-'80 full size pick-up trucks. Those have been known to have fire issues due to the Ammeter frying and the connector on the firewall overheating.

[JACook]

The Ammeter lore is based on GM and early Mopar-style ammeters that used to route all of the electrical system
current through the ammeter. People that apply that logic to Ford ammeters are simply ignorant, or trying to sell
you something, or both. I don't know exactly when Ford started using the shunt-type ammeters, but I do know
it was prior to 1964.

A shunt-type ammeter does NOT route all the system voltage through the ammeter, it simply measures the voltage
drop across a length of wire in the harness that is the main path into and out of the battery. The voltage drop across
the wire in the Ford system is very small, on the order of 50mV for full gauge swing. So it's more accurate to say
that the Ford ammeter is actually a very sensitive voltmeter.

Early Mustangs used to have one leg of the shunt crimped inside the harness, and the other leg was on a separate
ring terminal that went on the battery cable side of the starter relay. I have seen malfunctions where a loose terminal
would cause the ammeter to peg, depending on how the terminals were stacked. And while I never saw it smoke an
ammeter, I can certainly see how it could. But Fox ammeters have both wires crimped within the harness, eliminating
even that exposure.

The only reason most people have never seen a functional ammeter in a Fox Mustang, is simply because time has
oxidized the connections, or the shunt wire was bypassed during an alternator upgrade. It's an easy fix, IF you're
already pulling the dash for a heater core replacement...

[PaceFever79]

Thanks for explaining things.

[Hissing Cobra]

Jeff, I'm in awe of your knowledge. Time after time I see you post "well thought out" replies that make sense and it's good to know that we have someone on this forum that has all of the answers to most issues!

[grabbergreen84]

Jeff, I'm in awe of your knowledge. Time after time I see you post "well thought out" replies that make sense and it's good to know that we have someone on this forum that has all of the answers to most issues!

X2! I still say that if all of your posts here were compiled into a book, it would blow Kirschenbaum, Probst, Farr and Heasley and all of those guys completely out of the water.

[MrFoMoCo]

If there was an issue with amp meters causing fires in literally millions of cars I believe the public would have been well aware of it. And it would have been blown way out of proportion by the media.

[PaceFever79]

Thanks guys the question was just floated after seeing older cars having electrical fire, and wondering if this was something to be proactive about during a restoration. I feel sufficiently informed this particular issue is not an issue with our Foxes. Thanks to Jeff and all who commented.