Positive ignition source question.

[Big bill]

I was wondering what would be the best place to connect to a positive switched ignition source I’m installing an electric fan, relay ,any ideas or thoughts would be greatly appreciated thank you

 

[Jerry Hall]

As long as you are using a relay, I would come from the back of the fuse box. Something like the radio fuse. That should not create unnecessary load on the electrical system, as you are only powering the relay. Power the fans directly from a battery source under the hood.

 

[Geoff 2]

^^^^^. This. The common Bosch 30 amp relay coil only draws about 1/6 amp so it can be connected to any existing cct as power source for the relay.

 

[Big bill]

Thanks for the input.

 

[72RoadrunnerGTX]

Radio fuse? The radio is on the accessory ignition switch position. The primary side a fan control relay should be on Ignition 1, run only position. Won’t find that at the fuse box, dark blue wire in the engine harness or at the ballast resistor if stock original. If the charging system is stock/original with a correctly functioning ammeter, added loads should not be connected directly at battery. All added loads need to go on the alternator side of the ammeter, as are all factory vehicle loads. The alternator is the primary power source while the engine is running. Connected to the battery the fans will draw their current through the ammeter and related wiring while in operation.

 

[72RoadrunnerGTX]

....That should not create unnecessary load on the electrical system, as you are only powering the relay. Power the fans directly from a battery source under the hood.

Factory original charging system? Connecting to the battery certainly will overload the ammeter and related charging system wiring/connections while in operation.

 

[Jerry Hall]

Factory original charging system? Connecting to the battery certainly will overload the ammeter and related charging system wiring/connections while in operation.

As I stated in my post, the only drain on the original wiring system is the relay. Powering the fans from the battery will not have affect the ammeter and related wiring because the draw is directly from the battery. The ammeter and associated wiring only tells the alternator when to charge the battery via the voltage regulator. If you have a heavy load on your battery, the alternator will only charge the battery more. It has nothing to do with a load on the ammeter. The only extra load on ammeter and associated wiring is the relay no matter how you power the relay, be it ignition 1, or any other switched source.

 

[72RoadrunnerGTX]

Powering the fans from the battery will not have affect the ammeter and related wiring because the draw is directly from the battery. The ammeter and associated wiring only tells the alternator when to charge the battery via the voltage regulator. If you have a heavy load on your battery, the alternator will only charge the battery more. It has nothing to do with a load on the ammeter. The only extra load on ammeter and associated wiring is the relay no matter how you power the relay, be it ignition 1, or any other switched source.

You too eh? That is not correct, dead wrong. On a stock Chrysler charging system from this period, any loads placed at the battery while the engine is running, pulls it’s current from the alternator, through the ammeter and related circuit, up to the alternator’s max output while the engine is running. This current can be seen on the ammeter as it will register as false charging current on the ammeter. Again, the alternator is primary voltage potential device while the charging system is in operation, not the battery.
There should only be battery charging/discharging current flowing through the ammeter when the engine is running. All running loads must be on the alternator side of the ammeter as are all existing factory running loads.
Another way to look at it, while the engine is running, any loads happening at the battery (or anywhere on the battery side of the ammeter) will trigger an immediate response from the charging system to replace the current being drawn from the battery up to the currently available output from the alternator, less the current being consumed by loads correctly connected to the alternator side of the ammeter.

 

[Don Frelier]

But if you tie the fans in between the alternator and the ammeter you can mitigate some of the heavy current going into the bulkhead through the ammeter and back out.
You still may have a good current draw (discharge) from the battery in cases where the engine speed it not high enough for the alternator to supply the required draw.

 

[Geoff 2]

72RR,
You keep persisting with this nonsense about the charging system. Post # 7 is correct.

Look at the Chrys charging system below ~1971. The ign system is connected directly to the bat +ve terminal, as well as some other devices. Whatever device you connect to the bat direct, or to the alt stud, will show up as a voltage drop at the battery...because current is being drawn from the bat. The charging system will respond accordingly & increase the charge rate. You can add as many things as you like to the bat +ve terminal, as long as the current draw does not exceed the alts ability to charge. If you are pulling 80 amps from the bat & you have a 60 amp alt, you are going to have a flat battery.

 

[Rusty 72]

^ This.

 

[72RoadrunnerGTX]

72RR,
You keep persisting with this nonsense about the charging system. Post # 7 is correct.

Look at the Chrys charging system below ~1971. The ign system is connected directly to the bat +ve terminal, as well as some other devices. Whatever device you connect to the bat direct, or to the alt stud, will show up as a voltage drop at the battery...because current is being drawn from the bat. The charging system will respond accordingly & increase the charge rate. You can add as many things as you like to the bat +ve terminal, as long as the current draw does not exceed the alts ability to charge. If you are pulling 80 amps from the bat & you have a 60 amp alt, you are going to have a flat battery.

“persisting” yea, funny thing about facts, will aways remain as facts, can't be changed.

The notion that placing loads at the battery, or anywhere on the battery side of the ammeter, will not negatively impact the ammeter, bulkhead connections, and related wiring while in operation is complete and total nonsense. The information posted in Post #7 and previous posting in this thread, and your postings in the headlight relay thread, is completely wrong, not factual, in that regard.

The placement of loads does matter with an ammeter-based charging system of this type. The ignition system is not directly connected to the battery as you describe. The ignition system and all other factory operating loads gets power from splice 1, splice 1 is on the alternator side of the ammeter. Only the battery is on the battery side of the ammeter to be able to monitor battery charge/discharge rates only, as originally designed.

So, you place your add-on load to the battery and the charging system responds to the voltage drop, how do you think this current will get to the battery to replace the current drawn by the added battery connected load? The source of this added charge current is the alternator, correct? This added current is pulled through the ammeter, both bulkhead charging terminals, fusible link and all other related connections. This is no impact to ammeter or charging system? This current will register as charging current on the ammeter, it’s not really charging current is it? It places the entire original charging system outside of this original design limits. Mis-placed aftermarket loading at the battery is the number one cause of failed ammeter insulators and bulkhead terminal heat/melt-downs, always has been.

If your added operating load does not show as a discharge on the ammeter with the engine off, it is not loaded correctly.

If you can see your added operating load is showing as a charging current with the engine on, it is not loaded correctly.

Correctly loaded, engine running, battery fully charged, the ammeter should be centered, little to no current flowing through the ammeter while in operation. All operating loads having their current demands taking place on the alternator side of the ammeter, just like the factory loads. A constant charging indication is not correct and is an indication of incorrect loading.

Factory original Chrysler ammeter-based Charging System and additional loading. Load placement matters!

 

[69Bee]

You are both correct. There are 2 conditions (engine on/off) and 2 scenarios (fan load @alt/bat):

Engine off:
1) Fan load at battery: Battery is the source and no load is shown on the ammeter
2) Fan load at alternator: Battery is still the source, but a discharge will show on ammeter as current is being drawn from the battery

Engine on:
1) Fan load at battery: Alternator is the source and an additional load could be seen on meter as current is going thru ammeter
2) Fan load at alternator: Alternator is the source, but no additional load is shown on meter as current is supplied directly to fans (parallel path)

When the engine is running, the battery does not source any current to circuits as it is in a state of being charged by the alternator. The alternator is the source when the engine is running, as long as the load demand is not greater than the alternator can support, otherwise, any difference will be sourced from the battery. With the engine off, the battery will provide all of the current as long as the battery is capable of doing so, until it is discharged. The ammeter will only reflect a positive/negative current flow as long as it is between the load and the source. If the load/source on both on either side of the ammeter, nothing will be reflected on the meter.

 

[Geoff 2]

As I said in post #10, there is no problem connecting device to the bat +ve terminal, as long as the alt output can cover the extra load. [ Stated in post #10 ]. We have to assume that the manufacturer was smart enough to provide a thick enough wire gauge in the charging cct to allow full use of the alt output.

 

[72RoadrunnerGTX]

In this case the manufacturer was smart enough to design all the original factory operating load points, including those of all optional equipment, on the alternator side of the ammeter and to train their dealer network master techs about the consequences of loading at the battery back in the day. Wonder why the manufacture would go to all that trouble if load placement did not matter with this charging system as you insist.

Factory original Chrysler ammeter-based Charging System and additional loading. Load placement matters!

 

[72RoadrunnerGTX]

One last try, perhaps some flow diagrams would easier to understand for some.

First, bone stock loads, engine running, alternator keeping up with the stock loads.


Next, adding loads directly to the battery and resulting impact to the entire stock charge circuit.

Then, adding aftermarket loads without adding any additional current or current stress to any part of the stock charging system.

 

[Geoff 2]

And one more time, there is no problem connecting devices direct to the battery, as long as the total current draw does not exceed the alt rating. The middle diagram in the above post shows alt charging because it has, correctly, detected the voltage drop at the battery from the device
& is charging the battery.
Connecting additional devices at the alt stud causes the same voltage drop & the alt increases output accordingly. Might be easier to understand if there was no ammeter & just an idiot light, like many cars have.
In the diagram below of an idiot light charging system, exactly the same principle is involved. Numerous devices are connected directly to the battery because they may need to activated without the engine running/alt charging: power windows [ 40 amp cct breaker ], conv top, etc

 

[72RoadrunnerGTX]

And one more time, there is no problem connecting devices direct to the battery, as long as the total current draw does not exceed the alt rating. The middle diagram in the above post shows alt charging because it has, correctly, detected the voltage drop at the battery from the device
& is charging the battery.
Connecting additional devices at the alt stud causes the same voltage drop & the alt increases output accordingly. Might be easier to understand if there was no ammeter & just an idiot light, like many cars have.
In the diagram below of an idiot light charging system, exactly the same principle is involved. Numerous devices are connected directly to the battery because they may need to activated without the engine running/alt charging: power windows [ 40 amp cct breaker ], conv top, etc

Have I not prefaced every post/reply on this subject about the importance of load placement, that it only applies to these stock Chrysler unmodified ammeter-based charging systems from this time. This is not about idiot light-based systems, ammeter by-passed systems, voltmeter converted, or any of the other charging systems in 99.9% of the vehicles on the road toady. This is not about how the charging system responds to load caused voltage drop. It's about load placement does matter for these cars with stock charging systems. For the last time, if you place added loads at the battery, on these stock Chrysler unmodified ammeter-based charging systems from this time, the current the added load draws comes from the alternator not the battery while the engine is running, being pulled through the stock charging system components and conductors. They are not designed to handle this added current and failure of these components then becomes imminent over time. The ammeter is also then defeated in it’s designed purpose to register only battery charging/discharging current. The ammeter will register the actual charging current and your added load current together, showing as a false charging current indication. Bulkhead connectors and ammeter insulators have been burning up on these cars since they were new because of the described misplaced loading at the battery.

“Numerous devices are connected directly to the battery”? Not on these cars originally. Only the starter motor and start relay secondary are connected directly to the battery, charging system is not in operation while cranking, nothing to do with this subject. When charging system is not operating, the battery is only voltage potential device.

Do you know what the “fleet by-pass” is? Chrysler eventually by-passed the bulkhead charge circuit terminations with direct runs to a modified shunted 80amp ammeter on police/taxi and other fleet vehicles. Radios/lights and other add-on equipment would burn up charging system connections in short order when these loads were connected directly to the battery.

BTW, the optional factory power window relay and circuit breaker is connected to the alternator side ammeter stud on most of these cars from the time, not anywhere on the battery side of the ammeter. Once more, there are/were no factory operating loads at the battery or anywhere between the battery and the ammeter originally, by design.

I’ll be disengaging on this subject/thread now, pretty clear we're not getting anywhere, good luck.

 

[kaj750]

Hey! Look at me reviving a recent post for a change. haha.

Okay, okay. 1969 Charger. I need to run power to the relay for my fuel pump, the PDM for my EFI, and a switched source also to the PDM. I'm not familiar with Chryslers, specifically. And also not too familiar with anything pre 1995 LOL.
Could someone explain it to me like I was 12, where I should run power from? I don't know what nor where the ammeter, balast, etc are. I can find the fuse box, in the glove box, though LOL. I'm told these cars are very sensitive to being sure the electricals are on point.
Any help is more than appreciated. Thank you very much, in advance.
P.S. I have a factory service manual so am going through the diagrams.. just not too good at the terminology.

 

[Nacho-RT74]

I Was missed this thread! Is amazing that still showing the facts still there are persistent ppl thinking the batt is the correct source for acc!!


On a side note:

Radio fuse? The radio is on the accessory ignition switch position. The primary side a fan control relay should be on Ignition 1, run only position. Won’t find that at the fuse box

Actually since 72 there is a source on B bodies at least for the run circuit on fuse box which is in fact fused… for the seatbelt warning system.