Amp meter question

[jason340]

What would happen if you had done the amp meter bypass ( ran a wire from the alt to the starter relay but did not disconnect the amp gauge and the amp gauge had not previously burned out. Would the gauge just not work, or work slightly but not be accurate?

[dodj]

The latter. How much current it 'shares' with the parallel path is determined by resistance. Lots of people leave the amp gauge connected after the bypass. Personally, I prefer disconnection.

[Racer57]

Is the primary concern with the amp meter causing a fire because of the connecting blocks on each side of the firewall ? If so, how about running a new wire through the firewall bypassing the connection block ?

[jason340]

Not concerned, I just discovered that the amp meter that had been bypassed by the previous owner was good and I wanted to use it. The reason for the bypass was the nuts on the rear of the amp gauge were very loose and not making proper connection and in his haste he did not check that. He just did the bypass.

[dodj]

Is the primary concern with the amp meter causing a fire because of the connecting blocks on each side of the firewall ?

It's actually the gauge and the connections to it (usually). When an amp gauge carries ALL the system current, it is susceptible to heating up. If a connection corrodes a little bit, it will heat up even more. The heating/cooling of the connections eventually make the connection even poorer by expansion/contraction. Which creates more heat. Which creates a vicious circle creating even more heat which eventually becomes a dash fire.
Similar events can happen at the B/H connector. 

[msbaugh]

Look up the "Mad electrical" dodge ammeter fix.

The bulkhead and gauge are both fire (usually just failure) risks even when full alternator current is not flowing through them. My question is this, why keep an ammeter when the alternator current doesn't even flow to it anymore? It tells you nothing. 

In the mad electrical fix you wire alternator output straight to the starter relay (or some other junction block) that way charge goes straight to the battery rather than some backasswards path through multiple connectors. You then create a two wire power loop through holes drilled in the bulkhead to the inside of the car with fusible links straight from the same power junction. Much more reliable power and less voltage drop.

Buy a voltmeter.

This is all assuming you don't have a numbers matching original and you're going more for reliability.  There is a way to dummy your gauges so that the ammeter acts as a voltmeter but still looks original, I haven't tried it yet.

[jason340]

This is all assuming you don't have a numbers matching original and you're going more for reliability.  There is a way to dummy your gauges so that the ammeter acts as a voltmeter but still looks original, I haven't tried it yet.
[/quote]
I do have a matching numbers original car and I looked at the amp to volt conversion but I don't like the way the gauge goes all the way to discharge when the motor is off.
I am trying to reduce the load on the firewall connectors and the gauge by using the bypass and gauge.
I have read the article by Mad electric a while back and it has some great info on the proper way to fix the problem if you don't mind the modifications.

[chargerdon]

Ok... I like having an amp meter because it shows the state of charge of the battery and that the alternator works instantly!!  A volt meter doesnt really do that.

I have a 66 Charger with the amp meter still intact and original.     The bulkhead connector was showing signs of melting, so I put a wire straight thru it to get around this problem.   I am of the opinion that so long as I stick to the original size alternator of 37 amps, that there is NO problem with keeping the amp meter intact.   In addition there is a "bypass" of the amp meter for the headlights.. this being the biggest draw of current.   I live in NC and without air conditioning, and rarely need the heater blower, no power windows, there just isn't that much current ever being used.   I also am planning to put led lights into the tail.  Also, it is NOT a daily driver and I only put about 500 miles a year on it, mainly driving to local car cruises. 

I also have a 74 Challenger and still have its amp meter wired normally.   It still has the original alternator in it, I believe 50 amp and I will stick to that amperage.   In restoring this car I noticed two problem areas.   First the connector to the heater/air conditioning switch showed signs of melting.   That is no longer a problem as I now have Vintage Air air conditioner/heater and its power is directly connected to the battery.   (yes, I know its use therefore doesn't go thru the amp meter so that it isn't accurate when using either air or heater blower).   Secondly, I found previous owner bypassed the main power wire going thru the long flat connectors at the steering column as it showed signs of melting.   I also am planning on putting led lights into the tail lights.   So, again, the power draw actually going thru the amp gauge is simply for the ignition system and radio.   I rarely drive the car at night.   I drive it about 1,000 miles yearly, mainly to car cruises and an occasional car show.   So, i think it is ok. 

Oh, and NO I do not have any huge sound system in the cars, only aftermarket 200 watt stereos.   If i did that would change things.

Now, so long as i stick to original amp alternators, and drive 1,000 miles or less 95% of which is daytime, with both cars I think the chances of the amp gauge catching on fire is about 1 in 10000.  Chrysler obviously didn't do the best job on designing these cars electrical system, but, if you don't overload them with too high alternators and huge amplifier radio systems, I don't see a huge problem.   Heck their both over 40 years old and still working.

Or do  I have my head in the sand?

[jason340]

chargerdon
The car I have had this thread on is my 70 Challenger R/T but I also have a 73 Cuda and just like yours it has the original wiring, connectors and gauge. We have had that car for over 10 years and have had no problems related to the amp gauge so far. Yes, it is not a daily driver and it does  not have A/C or anything else that would have a big amp draw.
The only reason I started this thread was because the Challenger had the bypass wire in place and I found the amp gauge to be good so I would like to use it only with a reduced load.

[TelisSE440]

I have installed a 90 amp powermaster alternator in my 70 Challenger with a 4 gauge flexible bypass wire to the starter relay. The amp and bulkhead connector wires are installed as factory did. But the front lights, electric fans and electric water pump  draw directly current from battery. The wire shows no damage whatsoever in about 2 and a half years and the amp gauge works although it moves very little but i can understand if the battery is being charged or drained.

[jason340]

TelisSE440
Those are the results I was hoping to achieve. Thanks

[TelisSE440]

 

[Mopar Mitch]

     Light-weight 60 amp Denso future alternator to go into my Challenger... never had any bulkhead problems, just low electrical amps showing and dimmed headlights at low rpms/idle.... and very slow turn signal blinking.... currently have a nice factory chrome alternator ~45 amps??? (heavy).

[1970 RT Challenger 1970]

Tagged for interest

 

[duodec]

I still want to keep my car's ammeter. 

I've been debating both an inductive ammeter action installed into the factory gauge face (still requires the big wire to run through the bulkhead connector), or installing a milliammeter action into the gauge and using a large shunt resistor in the engine bay (two new small wires run through the firewall to the gauge).  The shunt resistors are available to handle up to hundreds of amps; just a matter of tuning them to the milliammeter mechanism.  And if the shunt ever failed it could be bypassed easily until replaced.  The one downside is that a fast acting very low amperage circuit breaker or fuse would be needed to protect the ammeter in the event of shunt failure.

The hard part would be rebuilding the gauge.