Ammeter/Alternator issue

[Juan Veldez]

So, after reading up a little bit on an alternator pushing more than around 60 amps, you should bypass the ammeter. Is that because it will "fry" the ammeter, fry the wiring, connections inadequate, or will it just peg the meter to the C and keep it there? Does anyone make an ammeter that looks like the original that will register what an 85 amp alternator puts out? What gauge wire for an 85 amp output alternator is suitable? I've seen 10 gauge being recommended. I am not running anything demanding a higher load than what was stock (no EFI, electric fuel pump, stereo amp, etc.). I bought a new under hood wiring kit (from Year One) and looking at the wires coming off the alternator, dang they look thin, which causes me concern after my research here on this site. I'm real close to initial start up, so I am making sure I don't have a CarBQ. Thanks in advance for any input, especially you Sparky!

 

[Challenger RTA]

One word explains the wiring and connections. Inadequate! Read Description and follow the dots. The wiring is not heavy enough and the connection were not designed to carry that much amperage 1:RED wire 16 Battery power yellow dot to splice one feeds fuse block, 2:charge wire 18 black wire blue dots to splice one through amp meter to red wire blue dot 16 to battery, 3:ACC feed from splice 1 Red wire Q3_12R yellow dot to steering column. Black wire 12BK red dot to ACC side of fuse box.ch load. The round back alt has an output of 37 to 45 amps max and the wiring is designed for that.
When everything is in good shape.

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[moparleo]

The problem is if the terminals on the Ammeter are loose or corroded. Poor connections/grounds generate a lot of resistance which causes heat buildup. As long as all connections have been thoroughly cleaned and grounds are done as well probably ok. Now any cut wires, worn insulation, poor splices etc... change that.

 

[72RoadRunnerGTX]

The stock ammeter with good, clean connections can handle a great deal of current. With stock loads, simply running a higher output alternator doesn’t change any current relating to the ammeter, all vehicle loads are sourced from the alternator side of the ammeter. With a healthy charging system there should be little to no current through the ammeter while in operation no matter what alternator.

That said, upsizing the alternator? recommend upsizing the charge circuit wires to at least 8ga and bypass the bulkhead terminals for this circuit, check the ammeter connections/insulators, leave the ammeter alone.

 

[72RoadRunnerGTX]

Only while the vehicle is not running or not charging is there any vehicle loads drawn through the ammeter. Again, as originally designed, healthy charging system, while in operation, there will be little to no current flowing through the ammeter, only battery charging or discharging current is registered as designed.

 

[Challenger RTA]

then where does the load go?

If you look at splice one and follow.all loads are connected at splice one.Headlight sw, ign sw that feeds acc of fuse box ,batt side of fuse box and R6 is the feed from alt. they are all hot at all times when battery is hooked up,There is power to the alt terminal through the amp gauge from the battery. One exception the starter is feed from the starter relay. Don't forget about grounds just as important.

 

[Challenger RTA]

You ask. Does anyone make an ammeter that looks like the original that will register what an 85 amp alternator puts out? no not that I know of. This is a different set up.I think it had an external shunt set up in the engine compartment. It would be better if there was a voltage gauge replacement instead. Actually this setup reads the voltage difference from the external shunt.so more less it a volt meter. That's what I recall I'll have to find the article.

 

[72RoadRunnerGTX]

then where does the load go?

Back to Mopar old-school, Jump ahead to 12:10 or so. All original loads are on the alternator side of the ammeter. The alternator is the primary power source while running.

 

[72RoadRunnerGTX]

You ask. Does anyone make an ammeter that looks like the original that will register what an 85 amp alternator puts out? no not that I know of. This is a different set up.I think it had an external shunt set up in the engine compartment. It would be better if there was a voltage gauge replacement instead. Actually this setup reads the voltage difference from the external shunt.so more less it a volt meter. That's what I recall I'll have to find the article.

The pictured “Police” 80 amp scaled ammeter actually has an internal shunt, it uses the same 40amp movement that most Chrysler passenger car ammeters of the time. Should be noted as well, the factory fleet/Police production also included a factory bulkhead by-pass and upsized wiring on the charge circuits.

 

[Challenger RTA]

Correct there is a wire ( shunt) under the hood in parallel with the amp meter shunt it would carry most of the load. the fleet amp gauges operate by reading the difference. so it actually acts like a voltage gauge. I had a two ramcharges 78 and 79.they didn't have a shunt.late 79 - 80 I think thats when they switched over to an external shunt like the fleet vehicles.
one can stack shunts on an amp meter to carry more load .but I wouldn't do it unless you know what you are doing! This is known as a remote shunt amp gauges. The stacking of shunts does not fix the issue of 12 ga wire and connectors.

 

[Challenger RTA]

If I recall Early A bodies 62 63 and fury my cousin had.had a shunt set up or what I though it was. there were two threaded terminals on the firewall. Then there was a 76 6 banger Duster we drove with no brakes used the parking brake. lost the headlights. could only drive in the day. took that as a sign to fix everything. found it had a shunt.

 

[moparroy]

Only while the vehicle is not running or not charging is there any vehicle loads drawn through the ammeter. Again, as originally designed, healthy charging system, while in operation, there will be little to no current flowing through the ammeter, only battery charging or discharging current is registered as designed.

That may be true - but if your battery gets depleted for whatever reason there can be a lot of current pushed from the alternator to the battery through the ammeter. For me that is when problems start. Call that an unhealthy charge system state but it does happen.

 

[Challenger RTA]

That may be true - but if your battery gets depleted for whatever reason there can be a lot of current pushed from the alternator to the battery through the ammeter. For me that is when problems start. Call that an unhealthy charge system state but it does happen.

I agree one has to take a scenarios into account in the real world.

 

[72RoadRunnerGTX]

That may be true - but if your battery gets depleted for whatever reason there can be a lot of current pushed from the alternator to the battery through the ammeter. For me that is when problems start. Call that an unhealthy charge system state but it does happen.

And you believe this temporary brief higher charging current can’t be handled by the ammeter? Many many Chrysler products back in the day suffered dead batteries, were jumped, battery recharged off the alternator and suffered no ammeter issues whatsoever. Ammeter can handle a great deal of current. Bulkhead charge circuit terminals melting/failing? Yes.

 

[moparroy]

Ammeter is not the issue - it is the connectors especially that are the issue - and for me the wires are undersized also. Might be fine when they are new but as soon as they start to oxidize with age then you get connection resistance which builds heat which leads to more oxidation and eventually corrosion and failure.

 

[Challenger RTA]

1977 I had a 2 door 69 Chrysler Newport 383 points regulator. Dead of winter dead battery.Would fire up and run with an other battery. would not charge. changed battery and regulator.This was my introduction of of the firewall connector problems. The battery will start and run the car fine no problems.I could drive all day and it would start. But when you start putting the acc on heater all the lights and others. The alternator picks up the load. AND what I found is the alt wire connection burnt but still made a bad contact. My Case and Point.

 

[FY1TopBanana]

I will show what is going on in the E body ammeter circuitry and the frailties. Much of the advice above is good.
There are several underlying reasons you need to be concerned about the E body charging circuit and ammeter wiring:

• the harness design for the E body originates on the engineering boards for B bodies about 7 years before the Challenger debuts
• the design features "in-harness" ties for battery, accessory, and ignition. Bear in mind these ties are soldered, tape wrapped and placed inline within the harness.
• the Packard 56 terminals are just that, terminals from 1956
• the ammeter circuit measures the current between the battery tie and alternator output. Period. Saying current only flows when this or that is happening =NOT. The ammeter registers a discharge when the battery is discharging or a charge when the alternator is charging the battery. The total current draw/supply is running through the ammeter!

Referring to below we are talking about R6-12BK and A1-12R. R6-12BK originates on port 18 of the bulkhead. Goes to the battery tie and on to the ammeter. Horn, headlights and the fuse panel battery side are also on this R6-12BK circuit. What protects them? We have to go to the engine harness side of the circuit.

Also note A1-12R is coming to the ammeter from port 16 of the bulkhead.

• 

On the engine harness side we see port 18 is fed directly from the alternator battery output. Port 16 connects to the battery positive through a fusible link. This link is the only protection on the wiring from the loads on the other side. Again, the ammeter is in the charge path between the alternator and battery. It "sees" both discharge and charge, all current to & from the battery passes through. Note an ammeter senses current flow without a ground. The circuit load itself is moving current (electrons) from positive to negative (ground) - the ammeter is sensing the (via a field) the current passing. A shunt "shunts" some of the current away from the ammeter and allows it to effectively read higher loads.

Now for the evidence. Look at the 18 port on this bulkhead. This is from a 35 amp alternator! The wiring was in good shape. The connections had been cleaned and mated with dielectric grease.

Here's the technical. The ampacity of wire - and we are talking about 12 gauge on this circuit here - is related to temperature and the wire's cross-section. 12volts DC has an ampacity table that's very easy to look up. The table's usually take a temperature limit of the wire plus some safety factory to rate the wire ampacity. In rough numbers at 12vdc/10 amps a 12 gauge wire is rated at about 15 feet. What you say? An E body alternator circuit must have about 15 feet of wire between the runs to the ammeter and back to the start relay. 10 amps. So as RTA above says the circuit isnt handling much current most of the time; a little charge, a little discharge. Until a short or other load comes along. Then its too late.. Running the headlights in low alternator output discharging the battery puts all this current drain through the ammeter and bulkhead to the battery tie. Things can get warm just with that load. Now deep discharge the battery so that on next startup the voltage regulator sees a low battery and juices the field and charge current to the max. Moparroy above correctly notes this case. Now we are getting hot. You see this fail isn't about a little current being sensed in normal operation.

What does a fuse in a circuit protect - the device or the wiring? If you said the device you misunderstand circuit design. The fuse protects the wiring always. At the device you can have another fuse to protect the device (like large audio power amps do) but that is separate. The E body circuit design is short on wiring protection.

BTW, a note on insulation. Mopar vintage wiring and cheap parts store PVC insulated wire has no place on your precious ride. Try a simple test. Take a piece of stock Mopar harness wire and a piece of new GXL or TXL wire. Put shrink tube on both, heat gun on high, and proceed to shrink both. The vintage or cheap wire will first bubble, then gas, then burn. The new cross-linked wire will tolerate multiples of heat the vintage wire does, and resist burning.

So what is the fix? Mentioned above it is pretty simple. There is no need for an ammeter in modern auto electrics. [There is an inductive ammeter you can use if you have a really sensitive load you want to run against a fixed battery ampere-hour budget, but in modern auto electrics the voltmeter tells us all we need to know about charging (13.7 -14.1v) and low battery (<12.1v) conditions.]

The Mopar ammeter bypass (short version):

1. remove both battery tie and alternator charge leads from the engine harness bulkhead ports. Route A1-12R lead through an open firewall grommet to its companion on fuse block side. (Speedo cable grommet can be swapped to get more through the hole.) Leave port 18 inside wire to power fuse block.
2. add fusible link or circuit breaker to alternator output and tie to start relay post common with battery.
3. remove ammeter leads and bolt (1/4-20) the 2 ammeter leads together and tape off well.

The alternator charge path is now direct to the battery and protected. The battery tie R6-12BK is fed through the bound ammeter leads.

Any alternator upgrade deserves a total rethink of your electrical system. If you are running a big alternator on a stock harness you have been forewarned. I run a TuffStuff 150 amp 3 wire. 6 gauge charge wire. Common battery post in firewall. Trunk mounted battery. #1 positive and ground bus front to rear.

I'm also experienced in total rewires and Infinitybox CANBUS + PWM power control installs if anyone is interested.

-Bill

 

[Challenger RTA]

Any alternator upgrade deserves a total rethink of your electrical system.
I concur! In a Perfect World. you set it and for get it. Even a new harness or redoing the connections are not going to cover the variables that are going to happen.Nothing fused at splice 1 or at any other splice or connection.That are of high current.( There are no primary and secondary circuits.) It's out dated and antiquated. the proof is in the pudding ,connector 18 in the picture. seen it so many times. To bypass the ammeter in my opinion.YES by all means!

 

[Challenger RTA]

I posted the wiring diagram to help other that don't have the experience or understand of the battery and charging circuit.Did not include voltage regulator circuit to save any confusion. As JUAN VELDEZ Ask: 1 more than 60 amps, you should bypass the ammeter.Not just my opinion a fact the wiring and connections are not rated for not that much more than it was designed for an alt 37 -45 amps. age doesn't help. If it's rating was not exceeded it would be fine. Bulkhead connector 18 is the proof of over heating for what ever reason. // Now my opinion there are a few ways to do it. A: With out changing to much. It could be removed and add if you are going for show points. Run a heaver gauge wire 10 or 8 ( 8 ga would be better) to the the starter terminal or to the starter relay. Leaving the original wiring intact If it's good. this would remove the high charging load from the bulk head connector. But not the acc load from the charging circuit. That being said.The original charging circuit should have a fuse or fuse able link right off the alt to protect the wire.The acc load,headlights,parking light,wipers,blower motor,and others. The acc load would be drawn through connectors not fused 16 and 18 that is fused. As far as the ammeter You may not see any meter deflection.It would depend on the condition of the wiring.Less path of resistance on connector non fused 16 and 18 fused. And no the ammeter does not need to be removed. Now it is a bridge between,not really functioning but electrically hot. One terminal can be removed heat shrink or tape or cut off. As the charging will be going the 8ga wire. circuit 16 and 18 and everything else in tack as original as it always was. I will post an other scenarios allowing this to be absorbed by myself and other to comment or correct.I'm not perfect and we all can help on another. I listen to everyone 2 cents and sometime it's a sense

 

[72RoadRunnerGTX]

The OP’s original question, as I understand, will the ammeter have to be by-passed if an alternator with a higher output capacity is swapped into place of the original spec. alternator with new reproduction wiring and all stock vehicle loads? Nothing about a complete redesign of the original charging system to modern specifications. Alternators don’t “push” anything, if the stock vehicle loads are not changing, there will be NO additional current flow anywhere. If any added loads remain on the alternator side of the ammeter, as originally designed, the ammeter current (battery charging/discharging) is not impacted whatsoever under normal operating conditions.

There is added potential charging current with a higher capacity alternator, as such, the conductors/connections should be sized appropriately for this added potential. Ammeters do not have to be by-passed under these stated conditions. Yes, the original 12ga conductors and Packard bulkhead terminals, and later Molex terminations proved to be under-rated in this circuit, even for the original spec. alternator. We were dealing with overheated bulkhead terminals at the dealers when these cars were relatively new.