Ammeter burnt out should I replace?

You have several ways of looking at this

1--Very heavy loads going through the ammeter is the basis of the problem with these cars, which is exactly what we are curing by doing things like bypassing the ammeter and using a voltmeter, or improving ammeter wiring

2--For the ammeter to "read correctly" all loads must be on the AMMETER side fo the ammeter, rather than the battery. This means that if you have loads -- fans, pumps, or landing lights -- hooked up to the starter relay battery stud or the battery, the ammeter, even though it should be "centered" with the battery up, will in fact show "charge" with one of these heavy loads on

3--So if you are willing to put up with incorrect readings during the use of heavy loads, you COULD hook them to the battery source rather than the ammeter.

The entire problem is that the

wiring for the charging line and battery feed are too small, and always was

the bulkhead connector terminals was never designed for that kind of current

the ammeter itself is limited for current capability

4woody,

Great question on where to source under-hood loads. I suggest direct wiring to BATT+ only momentary loads, like starter and horn, as the factory did. Everything else (electric fan, fuel pump) should source from the alternator output stud so they are metered thru the ammeter. As the current gets too big for the ammeter path, the diodes shunt it direct to the battery.

In my cars, I bring ALT+ over to the battery area with a big wire and have the diode shunt there. I have a modern relay box there, so a convenient place to supply loads.

As 67Dart273 says, if you come off the battery directly for a big load (electric fan), your ammeter would show "charging" since it sees only the alternator current flowing thru it, trying to keep up with the un-metered load. You really want to know if your battery is charging or (worse) discharging and you don't see the net current, so you might drive along blissfully thinking your battery is charging (forever?) while it slowly discharges if your alternator can't keep up.

A few side notes:

I recall seeing in some Dart wiring diagrams an optional "Accessory Power" feed directly off the battery into the cabin, without going thru the ammeter or even a fuse. I think for special accessories like Police spot lights. If you ran that accessory, you could run down your battery while seeing "charging" on the ammeter.

When young, you would see people driving on the highway with their lights on during the day. Parents said, "recharging their battery". I wonder if a similar issue above where an ammeter falsely showed "charge". Perhaps a quirk of GM or Ford "ammeters" (not real ammeters?). Might also have been that old mechanical voltage regulators needed a little load to kick them on and actuate the alternator field.

Here's what happens when 30+ years of weather and corrosion attack your bulkhead connector. Chrysler knew there was an issue with having a lot of current running through spade connectors which is why their fleet vehicles- taxis and police - had the wiring to the ammeter isolated and running through grommets in the firewall. My son had taken the car out for a spin and when he got home the dash lights and the dome light wouldn't turn off. Everything had melted together and they were back-feeding from the ammeter wiring. When I pulled the fuse block away from the bulkhead connector I could see that it had been taped up once before.

I just gifted this '74 B-body to my son. I rewired the dash beforehand by soldering Western Union splices and heat shrinking matching colored wires from our donor car. ( it was obviously taken off the road for an even worse melt down)

There's a lot of solutions but at the very least you need to inspect your wiring and look for any signs of overheating and look for corrosion or any signs of melting or overheating of the bulkhead connector. The first thing I did with my '70 Dart was to bypass the ammeter under the hood. I didn't want to have to do another rewire job. On his '74 we did the Chrysler fleet fix and ran everything through it's own grommets to the ammeter - no connectors at the firewall.

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I personally think that an ammeter is useles without a voltmeter and a voltmeter is even more useless without an ammeter.

The ammeter tells you what's happeneing to the battery, is it charging or discharging? Great info.
A voltmeter doesn't. But it tells you voltage which is useful fo when you have voltage regulator issue's like I had where the regulator would run the alternator at full blast untill it got hot and kicked in.

The ammeter let me know I had a major problem, just didin't let me know that there were times the alternator was pushing over 30 volts before the regulator kicked in. If I had known I had that kinda problem I would've stuck with unplugging the regulator and using a battery charger while parked while I scrounged for money for a new one. Instead I just took my chances and almost caught something under the dash on fire.

/6 Matt said:

I personally think that an ammeter is useles without a voltmeter and a voltmeter is even more useless without an ammeter..

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I disagree, to some extent, and "back then" much preferred ammeters. The thing is that if you "do something" like leave the lights on and run the battery down enough, the voltmeter might lead you to believe that the thing is not charging.

On an ammeter, if it doesn't run pretty close to center most of the time, such as when a battery starts to sulphate, get old, or develop a bad cell, it will start to "always show" some charge.

But I've pretty much thrown in the towel on this issue. Unless/ until I can figure out a GOOD remote shunt setup (and I just might) I'm sticking with a voltmeter, for the simple reason to get away from large, long conductors "up there" and back.

I've seen quite a few factory remote ammeters that aren't worth looking at. Quite a bunch of Ferd trucks I've see, including both my old 87 Ranger, and my 86, are so "numb" that when you get in and turn on the lights, it barely moves.

"We" actually dug into the harness of a couple of Ferds some 20 years ago, and lengthened one of the harness leads to increase meter sensitivity --IE made the "shunt" more resistance.

Very interesting thread!

ammeter shows that is probably charging. Volt-meter shows how much(correctly spliced into a good spot). Volt will show over-charge. Amp will show you kinda. You really just need to know volts; if high, bad connection, or reg shot.

Robj said:

Chrysler knew there was an issue with having a lot of current running through spade connectors which is why their fleet vehicles- taxis and police - had the wiring to the ammeter isolated and running through grommets in the firewall.

Click to expand...

As I mentioned, for those lucky enough to have a 1965, Chrysler fixed the "high current melts bulkhead" problem by using dedicated studs for the big ALT and BATT leads, as shown in the photo below of my 65 Dart in-work. These have thick wires soldered to the studs on the cabin side. My 1964 doesn't have this (though somebody did the "fleet upgrade") and I never read of 66+ cars having it. My guess is that it slowed down the assembly line too much so they dropped it.

Most later cars just run the engine harness thru a grommet in the firewall. At least the GM trucks I have robbed for HEI and knock sensors do this. It slows assembly, but is more reliable. Makes trouble-shooting a little harder, although pulling our Mopar firewall connectors for diagnosis can cause more problems than not. Sometimes the female connectors push into the housing when you plug the connector, so you should always verify they are fully in from the cabin side.

In my cars, most all leads other than ALT and BATT simply turn on relays in a modern relay/fuse box (90-95 Jeep). The only ones that carry load current are the turn signals. On the cabin side, the ACC wire from the key switch flips a 40 A relay, so the switch doesn't carry the load. I also use a relay for "blower high" position since I have dealt with enough melted L-M-H switches and vacuum climate switches (very expensive).

Before you fuss "old thread", I know (has it been 8 years?). I ran across a photo I had of the diode array mentioned above, cut in two and fit to make an "opposite-parallel" diode as 67Dart273 shows schematically. I am working on another diode fix for the convertible pump in my 1964 Valiant, so was poking in that folder. The current task would be easier if this diode array was the "CTR" variant ("reversed", common anode on baseplate). I could use it uncut and just ground the baseplate, but that model is rarer.

I bought a used pump for a 1994+ Ford, which is 2-wire vs the 3-wire type that both Mopar and Ford used earlier (now hard to source). I can make my switch (2 wires, each alternately hot, open when other is hot) work by adding two diodes. BTW, convertible pumps on U.S. cars are pretty generic. This one fit the Mopar shelf holes. Ford even used the same dual-bullet connector in the 1960's with red and yellow wires. Those owners have the same issue with the later 2-wire pumps.

LOLOL I forgot all about that "little trick"