What is the max amp alternator to safely run on my '65 Dart HP GT w/charger 273. Still has factory amp gauge and 5 amp regulated fuel/temp gauges. Stock wiring. Factory ac has been removed and no other added accessories. Found a 75 amp rated chrome unit I was thinking about using. any help appreciated.
Alternator amp rating.
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J Glenn
Well-Known Member
What regulator is on it, the original mechanical one? Or an upgraded (solid state) one? I would think the only limit would be, if you actually draw 75amps, the field coils have to be fed more current to increase the magnetic field in the alternator... and at some point I suppose the regulator either cannot keep up or could be damaged (or the wiring to/from the regulator) due to excessive current to the field coils. Just thinking outloud...
I would say the max amp alternator you can safely run, without any mods or updates, is exactly what it came with originally.
Replace the ammeter with a voltage gauge, and do the MAD bypass, and you might be good with the 75amp. Personally I would upgrade the entire charging circuit, but then again, I have a good reason for feeling that way..'69 wiring with a 65amp alternator
Replace the ammeter with a voltage gauge, and do the MAD bypass, and you might be good with the 75amp. Personally I would upgrade the entire charging circuit, but then again, I have a good reason for feeling that way..'69 wiring with a 65amp alternator
pishta
I know I'm right....
Its the harness that dictates the capacity limit of the system. You wouldnt want to run 400 psi through a 100 psi hose.....and the bulkhead connector...
J Glenn
Well-Known Member
OMG, I'm clearly too new to these old Mopars.. there's an amp gauge? Ya, you could melt that. I was assuming that going to the 75Amp alternator meant upgrading the wiring to anywhere you would be sending extra current (like to brighter relayed lights, and battery I suppose!, and whatever else). I rescind my post.... I'd stick with the original alternator... this amp gauge business is just crazy... get rid of that thing.
I saw Mopar Action has an article on this very topic this month.
And the simple answer is no you can't run the 75 amp alternator without upgrading some details such as wiring.
And the simple answer is no you can't run the 75 amp alternator without upgrading some details such as wiring.
slantsixdan
=..=
Disregard the halfaѕѕed advice from the Chevyheads at MAD Electric; there are numerous options for doing the upgrade properly. See here and here and here and here. An ammeter update can be done very cleanly without appearing hacked; how much it costs depends on whether you do the work yourself or have it done for you. Places like Redline Gauge (lousy website; guess they're too busy doing actual work) or Williamson's Instruments can do a stealth conversion of stock ammeter to voltmeter for "it must've come that way from the factory!" appearance as seen on this '62 Plymouth (also custom never-available-from-factory oil pressure gauge in place of the clock, and engine temp gauge calibrated with numbers instead of just "C" and "H").
Long time ago, (well, not that long, lol!), in the mid '80's I worked with a Gentleman in a private shop Who thought He'd upgrade His Omni alternator when it took a dump.
Later versions of the Omnirizons had the same gauge charge lead no matter which option, but early ones did not. Long & short of it, the first time the battery put enough
demand on it after a hard start & He tossed the headlights & blower on the cable started cooking then the fusible link gave it up. Car was maybe 6 yrs old & in good shape,
and Your car is how old?
Bottom line is there are many terminations with a lot of years on them, and even if they seem mechanically secure, it does not mean they are electrically intact. Time and
atmospheric conditions cause oxidation & material degradation, and You can't always tell just by looking at them. The OE wiring and system was barely up to the task it was
charged with(bad pun intended) for the low amp alternator it was teamed with when new. Don't play with fire, and if You're careless, that's what will happen..literally.
As far as a high output alternator "over-demanding" a regulator, it is exactly the opposite, a high output unit will have much less "ON" time & shorter duty cycles because
it can more easily keep up with the system demand. I haven't seen a mortal range alt. rotor exceed the capabilities of an OE regulator by current demand yet, but I haven't
seen everything so...................
Later versions of the Omnirizons had the same gauge charge lead no matter which option, but early ones did not. Long & short of it, the first time the battery put enough
demand on it after a hard start & He tossed the headlights & blower on the cable started cooking then the fusible link gave it up. Car was maybe 6 yrs old & in good shape,
and Your car is how old?
Bottom line is there are many terminations with a lot of years on them, and even if they seem mechanically secure, it does not mean they are electrically intact. Time and
atmospheric conditions cause oxidation & material degradation, and You can't always tell just by looking at them. The OE wiring and system was barely up to the task it was
charged with(bad pun intended) for the low amp alternator it was teamed with when new. Don't play with fire, and if You're careless, that's what will happen..literally.
As far as a high output alternator "over-demanding" a regulator, it is exactly the opposite, a high output unit will have much less "ON" time & shorter duty cycles because
it can more easily keep up with the system demand. I haven't seen a mortal range alt. rotor exceed the capabilities of an OE regulator by current demand yet, but I haven't
seen everything so...................
67Dart273
Well-Known Member
I put a 60 amp alternator in a 65 Barracuda because it was what Advance Auto had in stock. It was actually for a 75 D100. I grounded one of the brushes to use with older voltage regulator. It burnt up the regulator so I installed a VR706 from Auto Zone and no problems since.
slantsixdan
=..=
…yet. :-(
67Dart273
Well-Known Member
Some of you are buying trouble and a couple of you "are not." SOME YEARS of the early A bodies had a robust feed through for the ammeter circuit, 65 was one. "I forget" what else.............
66 and later do not............
65 bulkhead connector:
66 and later do not............
65 bulkhead connector:
Alternator only will supply what is demanded. It doesn't put out 75 or 100 or whatever unless there is equipment calling for it.
Alternators capacity to produce power goes up with rpm. The 'rating' of Alternators by the aftermarket is based on whatever, but if they are somewhat honest, its usually near maximum and based on 14 something Volts. Changing the voltage is one way to play games with the 'rating'.
The ammeter is a monitor of the battery current flow - NOT the alternator output. Having a high rated alternator will not increase the current the ammeter sees unless the battery has been really run down. If real lucky, the high rated alt might reduce the loads on the ammeter IF it makes more power at idle speeds. Some do, but others trade off low speed performance for better high speed output. When an alternator can't supply enough power at idle, then power is drawn from the battery.
Alternators capacity to produce power goes up with rpm. The 'rating' of Alternators by the aftermarket is based on whatever, but if they are somewhat honest, its usually near maximum and based on 14 something Volts. Changing the voltage is one way to play games with the 'rating'.
The ammeter is a monitor of the battery current flow - NOT the alternator output. Having a high rated alternator will not increase the current the ammeter sees unless the battery has been really run down. If real lucky, the high rated alt might reduce the loads on the ammeter IF it makes more power at idle speeds. Some do, but others trade off low speed performance for better high speed output. When an alternator can't supply enough power at idle, then power is drawn from the battery.
So how is the battery charged? Let’s say after some extended cranking on a cold day, then some exdended idling as things warm up, once the rpms come up the battery is low.. will the alternator attempt max output to recharge as quickly as possible, or will it slowly recharge the battery?
If its real low, yes it will try to max out the alternators output. I don't know the the limit on charge demand, maybe it won't take 100 or 200 amps but nor will the fusible link... ha!
My observations have been that after extended cranking the battery might draw 10 to as much as 25 amps at the beginning of recharge. In a few minutes it will be down to 5 amps or less.
When a battery is really run down from something like leaving the parking lights on all day, then the battery will try to draw 30 or more amps. That's when its best to let it idle and keep the speeds down when driving. Because yes, as soon as the rpms come up even stock type alternator can deliver 35, 40 amps or more - and if nothing else is on - then everything but what is needed for ignition is going through the ammeter to the battery. When I've had to do it, I've turned the headlights on and shifted in N at every opportunity. The other bad thing about so much current to the battery is the battery gets hot - worse the AGM types. Hot battery doesn't charge as well and can also boil off battery acid. So 15 -20 minutes of even that much is really the limit, some would say too much. Let it cool down and it will charge a heck of a lot better the next round.
With a battery charger, there's generally a lot more control. Get it going and see the current draw, if its too high, cut it back a bit so it doesn't get hot. I took some pictures last time I was using an old charger. This one originally had a thermostatic probe to stick in one the cells. Lets see if I can load up the sequence.
OK. Here we go.
Turned the dial up 'til my voltmeter showed 14.2 Volts across the battery's terminals - typical system voltage for most vehicles. Then notice the current draw.
So after a minute, I cut it back to 13.3 Volt and its 10 amps. OK, that seems reasonable.
My observations have been that after extended cranking the battery might draw 10 to as much as 25 amps at the beginning of recharge. In a few minutes it will be down to 5 amps or less.
When a battery is really run down from something like leaving the parking lights on all day, then the battery will try to draw 30 or more amps. That's when its best to let it idle and keep the speeds down when driving. Because yes, as soon as the rpms come up even stock type alternator can deliver 35, 40 amps or more - and if nothing else is on - then everything but what is needed for ignition is going through the ammeter to the battery. When I've had to do it, I've turned the headlights on and shifted in N at every opportunity. The other bad thing about so much current to the battery is the battery gets hot - worse the AGM types. Hot battery doesn't charge as well and can also boil off battery acid. So 15 -20 minutes of even that much is really the limit, some would say too much. Let it cool down and it will charge a heck of a lot better the next round.
With a battery charger, there's generally a lot more control. Get it going and see the current draw, if its too high, cut it back a bit so it doesn't get hot. I took some pictures last time I was using an old charger. This one originally had a thermostatic probe to stick in one the cells. Lets see if I can load up the sequence.
OK. Here we go.
Turned the dial up 'til my voltmeter showed 14.2 Volts across the battery's terminals - typical system voltage for most vehicles. Then notice the current draw.
So after a minute, I cut it back to 13.3 Volt and its 10 amps. OK, that seems reasonable.
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This battery wasn't too far down. In fact I just driven it, but there was a problem with charging (GM 12SI - don't blame Ma for this one, its an AMC Jeep) so it didn't have enough left in it to start again.
15 minutes later, same power positon on the rotary switch, the current has dropped a little and the voltage driving it has come up.
I let it slow charge for another hour, because I could.
15 minutes later, same power positon on the rotary switch, the current has dropped a little and the voltage driving it has come up.
I let it slow charge for another hour, because I could.
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I put a 100 amp powermaster alternator on my 68. Besides bypassing the bulkhead connector and the solid state regulator everything else is stock. It fixed the low rpm stall issue I was having with the hei conversion... it charges very good at low rpm. As long as my battery is in good shape I don't see any problem with it because it shouldn't put out any more than the stock system needs, I don't have any additional accessories that would overload the original wiring or amp meter. If you stuck a dead battery in there and took off down the highway I bet I would need a fire extinguisher.... but I don't plan on doing that.
I’d like to see the oem ammeter on a test bench pushed to failure.
I guess the real danger though is the bulkhead connector, and the fact it was designed to handle the 30amp alternator, in its prime..Even bypassed, I would still feel nervous about pushing over 3x what the factory wiring was built for, 50yrs later
I guess the real danger though is the bulkhead connector, and the fact it was designed to handle the 30amp alternator, in its prime..Even bypassed, I would still feel nervous about pushing over 3x what the factory wiring was built for, 50yrs later
They vary from vehicle to vehicle. They're not all built the same. The ones on trucks should have been more robust, but plenty were not. Why trucks different? Because plows and winches are wired off the battery and when that's done, the battery demands for recharging are high and frequent.
Its one of the weakest links (although there are exceptions as pointed out above by 273). Packard 56 terminals really not great to be carrying more 20 amps for long periods of time. On most A-bodies, another weak area is the minimized wiring to the headlights. Too many connections, long route, wires at near max capacity for load (eg 18 AWG for the final runs from the hi/lo switch).
Factory offered at least 3 alternators for much of the 60s. Getting back to the original question, the shop manual test is not the same as the "rating". The test was at 1250 rpm and 15 V - that gives you a better idea of what it can supply while doodling along at 25 mph. The higher rated alternators have more windings, which means more copper so cost more. The factory wasn't putting them in unless there was a real need or the customer was willing to buy it as an option. That's what was going there. "30 amp" was the lowest in '66.
http://www.hamtramck-historical.com/images/TSBs/1966/66-78_page2.jpg
FSM vs. rating and a graph of a 15Si alternator's power vs. rpm here.
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67Dart273
Well-Known Member
You don't even have to push "3x" through some of them depending on the year. A great example is the one right on the MAD site:
............and I've seen SEVERAL of those more than a dozen perhaps, and I'm not even a pro mechanic. "Up here" many used to put driving lights, winches, and snow plows on Ramchargers and Dodge trucks.
But even WITHOUT THAT the ammeter failure mode is typically this:
1.....Some years the cluster housing/ mounting for the ammeter is made of soft plastic.....you warm it up, it gets soft and loose. The ammeter studs go through that and depend on it to remain "tight."
2.....The ammeter studs where they hook to the internal shunt/ "guts" of the ammeter are NOT welded/ brazed/ soldered. They depend, simply, on the pressure of the mounting nuts, see (1) above
3....Even without the plastic housing in (1), the ammeter must have fiber insulating washers, and if anything is loose enough to heat, and enough current WILL heat it, then the washers deform, soften, loosen, cook, crack, etc etc AND THE CONNECTIONS come loose
One website I've come across advocates soldering the studs to the shunt.....but you STILL have to have the nuts tight on the wiring
4.....Last, and this happened to me........the wire ring terminals themselves can fail on the end of the wires, causing..........heat......and ........failure.
I damaged an ammeter in my 70RR back in the 70's and I had no where near "3x" the amperage through the ammeter
Here is one article on ammeter damage and repair:
Bullet-Proof Your Ammeter (A 'How To') - DodgeTalk : Dodge Car Forums, Dodge Truck Forums and Ram Forums
Heated/ corroded/ damaged ammeter studs
Cleaned up and soldered
Having said all this, I LIKED ammeters, but rather than put up with what I've run into in the past, I'll gladly eliminate the darn thing.
Your other choice is to engineer yourself an external shunt ammeter like the later vehicles used, along with Ferd and GeeMsee
James Camp
no mopar
is it best to cut the wires going to ammeter and splice them b4 they pass thru the bulkhead connector,or does it take the heat off the wires if you take them loose behind dash cluster and splice them under the dash ?
The way to take heat off the wires is use proper size, have good clean junctions, and not to overload them. They only get hot where there is resistance. A 10 or 12 gage wire that's not too long can take 30 amps for a while without getting too hot.*
There is no one 'best' method of wiring or rewiring. It depends on the year and model, and what problems it has or modifications are done.
On a standard original A-body arrangement, the main junction is under the dash. If there is a problem with the ammeter connections, you can put the two ring terminals together. If there is a problem elsewhere, such as at the bulkhead connector, then that's what should be addressed.
If you are looking to reduce the number of junctions or increase capacity, adding parallel wires is the simplest solution. Run the wires through a insulated grommet in the firewall. Diagram below.
(The ammeter and wires to it only carry current when the battery is running the car or being recharged).
*edit: based on your other thread - You're in a situation where you want to let the alternator provide a high current charge to the battery? I think the way to do that is use a deep cycle battery and either
(a) wire the battery positive direct to the alternator using a 10 gage wire and 14 ga fusible link.
(b) look up Bill Grissom's method of redirecting high current flows to a bypass similar to (a) while allowing low current to use the stock system.
I say this because the stock ammeter and terminal connections at the bulkhead, ammeter, solenoid relay and link are all likely to be points of resistance when putting over 40 amps through them for any length of time.
However if there are any other high current devices on the system, then a second parallel wire from the alternator to the main junction or fusebox may be needed as well. Or go with relays and fuses.
There is no one 'best' method of wiring or rewiring. It depends on the year and model, and what problems it has or modifications are done.
On a standard original A-body arrangement, the main junction is under the dash. If there is a problem with the ammeter connections, you can put the two ring terminals together. If there is a problem elsewhere, such as at the bulkhead connector, then that's what should be addressed.
If you are looking to reduce the number of junctions or increase capacity, adding parallel wires is the simplest solution. Run the wires through a insulated grommet in the firewall. Diagram below.
(The ammeter and wires to it only carry current when the battery is running the car or being recharged).
*edit: based on your other thread - You're in a situation where you want to let the alternator provide a high current charge to the battery? I think the way to do that is use a deep cycle battery and either
(a) wire the battery positive direct to the alternator using a 10 gage wire and 14 ga fusible link.
(b) look up Bill Grissom's method of redirecting high current flows to a bypass similar to (a) while allowing low current to use the stock system.
I say this because the stock ammeter and terminal connections at the bulkhead, ammeter, solenoid relay and link are all likely to be points of resistance when putting over 40 amps through them for any length of time.
However if there are any other high current devices on the system, then a second parallel wire from the alternator to the main junction or fusebox may be needed as well. Or go with relays and fuses.
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