Alternator wiring question.

[BLK 68 R/T]

I'm looking into doing the amp gauge bypass wiring upgrade to my car (68 charger, 440) but have another question to pose before I do it. By leaving everything hooked up stock and adding another main charge wire from the alternator stud directly to the starter relay. Does that remove any of the load from the amp gauge and help out the problem of the possible melted firewall connections and shorted amp gauges? Just curious, thanks for any input.

[Pete in NH]

Hi,

Just adding the second wire from the alternator to the starter relay will take some of the load off the ammeter path but it is very difficult to say how much. You would have two parallel paths the current could flow through and it would depend on the resistance of each path. This would also create a safety issue unless you put a fuse or a fusible link in the second path. This solution helps the bulk head connector pins a bit but in the long run creates other issues.

It really depends on the size of the alternator as to what the best upgrade solution would be. If it's a stock size alternator I would just do what Chrysler called a "fleet wiring upgrade" which leaves the stock ammeter but eliminates the problematic bulk head connector pins. If the alternator is larger than stock (45 amps) I would eliminate the stock ammeter and go to a voltmeter and run the alternator output directly to the battery terminal on the starter relay though the appropriate size fuse or fusible link.

[BLK 68 R/T]

Hi,

Just adding the second wire from the alternator to the starter relay will take some of the load off the ammeter path but it is very difficult to say how much. You would have two parallel paths the current could flow through and it would depend on the resistance of each path. This would also create a safety issue unless you put a fuse or a fusible link in the second path. This solution helps the bulk head connector pins a bit but in the long run creates other issues.

It really depends on the size of the alternator as to what the best upgrade solution would be. If it's a stock size alternator I would just do what Chrysler called a "fleet wiring upgrade" which leaves the stock ammeter but eliminates the problematic bulk head connector pins. If the alternator is larger than stock (45 amps) I would eliminate the stock ammeter and go to a voltmeter and run the alternator output directly to the battery terminal on the starter relay though the appropriate size fuse or fusible link.

Thanks for the information. Yes, I plan on upgrading the alternator to a powermaster, 2 wire, 75 amp alternator. I will be running an electric fuel pump, A/C and possibly electric fans. It sounds like the best thing to do is proceed with the amp gauge bypass, and install a voltmeter. Looks like I have some wiring to look forward to!

[xoman60]

Hi,

Just adding the second wire from the alternator to the starter relay will take some of the load off the ammeter path but it is very difficult to say how much. You would have two parallel paths the current could flow through and it would depend on the resistance of each path. This would also create a safety issue unless you put a fuse or a fusible link in the second path. This solution helps the bulk head connector pins a bit but in the long run creates other issues.

It really depends on the size of the alternator as to what the best upgrade solution would be. If it's a stock size alternator I would just do what Chrysler called a "fleet wiring upgrade" which leaves the stock ammeter but eliminates the problematic bulk head connector pins. If the alternator is larger than stock (45 amps) I would eliminate the stock ammeter and go to a voltmeter and run the alternator output directly to the battery terminal on the starter relay though the appropriate size fuse or fusible link.

What other issues are you talking about besides the fuse being needed?

[Pete in NH]

Hi,

Just adding the second wire from the alternator to the starter relay will take some of the load off the ammeter path but it is very difficult to say how much. You would have two parallel paths the current could flow through and it would depend on the resistance of each path. This would also create a safety issue unless you put a fuse or a fusible link in the second path. This solution helps the bulk head connector pins a bit but in the long run creates other issues.

It really depends on the size of the alternator as to what the best upgrade solution would be. If it's a stock size alternator I would just do what Chrysler called a "fleet wiring upgrade" which leaves the stock ammeter but eliminates the problematic bulk head connector pins. If the alternator is larger than stock (45 amps) I would eliminate the stock ammeter and go to a voltmeter and run the alternator output directly to the battery terminal on the starter relay though the appropriate size fuse or fusible link.

What other issues are you talking about besides the fuse being needed?

Running a wire from the alternator output to the battery stud on the starter relay even through a fuse with the original ammeter wiring in place creates  two parallel wiring paths. You can not be sure exactly how the current flow will divide. Since the new wire will likely be heavier you could assume more of the current will flow through it, but, how much?

Also, the load current for the car to the distribution point called" the splice joint " will still flow through the ammeter. So you will have an ammeter that would show all the discharge current but very little of the charge current. All the load current will still flow through the bulk head connector pin from the battery.

Also, theoretically the current that could flow from the battery to the alternator in case of a short in the alternator would be the sum of the current rating of the original fusible link plus the fuse in the new wiring path. Although this is possible it is not likely but I would rather respect the very high currents the battery can produce into a short circuit.

If it were my car I would run a new wire from the alternator output to the starter relay battery stud fused at slightly above the alternator  current rating. Then I would run a new wire from the starter relay battery stud through a 50 amp fuse to the splice joint. I would then remove all the original ammeter wiring through the bulk head connector and convert the ammeter to a volt meter. This would be all in reference to using an alternator considerably over a stock unit in current output. 

[xoman60]

Yea, I have read about what your talking about and it sounds good. I know a lot of people seem to do that. I've also read what nacho has said about removing the amp meter. I kinda like the amp meter. I'm not sure why. Probably because I want to keep my gauges stock appearance. I recently changed my alternator to duel field with a new 1970 and later voltage reg along with a new wiring harness. My amp needle stays just maybe a 1/4 inch to the right of center now when the rad fan is on. The idle charge is much better than what it was also. I think the output is only 50 amps on the new alternator so pretty close to oem.  My bulkhead connector looks pretty good and I put a good coat of dielectric grease on it. I was going to add that second wire to the starter relay stud for the hell of it but maybe I should just leave it alone for now. I need to restore or replace all my gauges, tac and speedo also, so I will add the wire then all the way to splice joint. Thanks for the info PETE.