55.2-59 alternator conversion, now doesn’t start

[ApacheProject]

Hello,
I finally got around to installing a alternator in my ‘58 Apache/283, it had a generator originally.
Ordered an alternator conversion harness from EBay ( same as others sold online), followed instructions and now truck doesn’t start. I suspect they left out something in the instructions, I checked and my ignition switch doesn’t have any power at the Batt terminals. Any suggestions?

[leegreen]

60+ year old truck, does the wiring still match factory?
Still have a working ammeter? Ignition switch gets power from ammeter I believe.

I've seen cheap ebay harnesses where they forgot to strip a wire before crimping the connection, so testing the harness might be time well spent

[ApacheProject]

Truck has new factory type harness from American Auto Wire, was running fine before conversion. I also thought the ignition gets power from the Ammeter, if you see in the instructions they say to remove red wire from ammeter and replace it with red wire from new harness. I think by doing so the ignition no longer gets power. Could I run another wire to the ignition from the ammeter?

[dsraven]

have you lookad up any wiring diagrams for the alternator? I assume it is a 3 wire 10si delco?
https://www.google.com/url?sa=t&sour...WFZlqLcrdn2rdD

[mr48chev]

I'm thinking that you disconnected wire that feeds power to the inside of the truck.

This is a diagram I have used a few times to convert a generator rig to internal regulator alternator .

Study it a bit and you might figure out where you disconnected a wire that needs to be connected.

[ApacheProject]

Yes, it’s a 3 wire alternator. I looked at the original harness and the red wire that the instructions wants me to disconnect is in fact the wire that goes from the Ammeter to the top wire on the ignition switch three prong connector. So, I’m not getting power because of that. Should the two “batt” connectors also have power? I was thinking of plugging in the original red wire back on the Ammeter using the upper blade connector. Like I said that only connects to the 3 prong connector.

[dsraven]

if you look at the diagram that mr48 posted you will see the alt output is connected to the battery through the wiring at the horn relay junction. an alternator won't supply power until it is turning so using it as the sole power supply to the truck wouldn't supply any power to the system in order to actually start the truck. the ammeter needs to be run in series back to the power supply for the truck circuits so it can sense the total power draw or charge. dunno if that makes sense?
here is a link to the hamb where they talk about installing an amp meter.
if you wire the amp meter in series with the alternator output it will tell you the alternator output. if you put it in series between the battery and the main power wire for the truck it will tell you the current draw that is being used unless your alternator is wired into the circuit after the amp gauge-in this case the amp gauge may simply stay at zero because the alternator is supplying the required juice that the circuit loads are using. if you have a 100 amp alternator and you wire the amp gauge in series from the alt to the battery then you would need a gauge that will handle at least that. not too many times your truck circuits will draw 100 amps, but the dead or very low battery may have a high draw requirement and that could cook the old amp gauge. think through how you wanna wire it up so you can use the original amp gauge, if that what you're using.
does that make sense?

[dsraven]

https://www.jalopyjournal.com/forum/...-light.670214/

sorry, forgot to paste the link in the last post

[ApacheProject]

I’m sorry but this is getting confusing. There has to be someone who bought this type of conversion harness and made it work. I think the instructions left out the part where the ignition gets power from after the swap. Everything seems right until connecting to the Ammeter. The only connection to the ignition switch is the brown wire that goes to “ ACC “, there has to be more going to the ignition switch.

[mr48chev]

The wire connected to the accessory side of the ignition is the exciter wire for the alternator.

I don't want to sound condesending in any way but I feel that you threw your money away buying that kit as it is all too simple to correctly wire them up yourself.

This is the way a lot of guys hook up an internal regulator alternator (10 or 12 SI) from scratch


This diagram matches what you have there in that kit except the exciter wire on the kit doesn't use a diode and goes to the accessory side so it won't feed power back to the igniton when you turn the key off.




A bit different but simple


I'm thinking that those instructions have you discnnecting all power to the inside of the cab.

Get your test light out and see if you have power to the Batt post on the switch, if you have 12 + volts no problem if you have 0 volts you need to reconnect the wire that those instructions had you disconnect.

First check the horn relay where their horn relay connection wire hooks up. you have have full time 12 Volts at that connecton. You do not remove the wire from the junction block or battery to the horn relay.

You can do the"this wire goes here and that wire goes there " by studying the diagrams I posted and comparing them to the harness.
v

[ApacheProject]

Bingo! It worked. I reconnected the original red wire above the “new” red wire at the Ammeter and it cranked right up. Thanks
Also have a voltmeter gauge under the dash that shows 12+ while running.

[dsraven]

running should actually show more like 14volts. it may depend on where the volt meter is sensing though
good to hear you got it figured out, maybe do a voltage test at the battery, ensuring the battery connections are good and clean, like shiny lead showing under the battery terminal clamps. does you amp gauge also work?

[ApacheProject]

Yep, It’s a cheap gauge that I had. It doesn’t have the best connections, it use to to read 10 volts before I did the swap. I plan to install a better set next. Thanks

[1project2many]

It's good that you've figured out the issue. The original wiring routes all power to the battery through the ammeter so breaking that connection disconnects "everything" from the battery.

I think it's important to mention the original ammeter can fail and / or burn up if charging current exceeds about 30 Amps for any length of time. Most of the early "SI" family alternators were 35A in the '70s and the output has only increased. It's possible to create a "shunt resistor" to reduce the amount of current that passes through the alternator. GM did this in the '60s to make OE ammeters safer when they changed over to alternators.

[jwhotrod]

the first thing you should have done is remove the ammeter from the circuit completely they are dangerous and have been the source of many electrical fires that have destroyed cars. in order for the gauge to read properly, all the current in the truck must run thru it. it is much safer and more descriptive to have a volt meter which will not cause a fire, if you have the wiring diagrams from your Autowire harness you should be able to do that easily. if youve ever seen an electrical fire in a car this would have not been a question at all.

[mr48chev]

The key word there is load, If you start adding accessores ammeters cannot handle the load. If the truck doesn't have a bunch of accessories like a sound system with an amp, power windows, power seat, Heat/AC, power seats it will still work. If he is adding accessores that draw power then yes it is prudent to change to a voltmeter. Just a heater and plain simple radio and headlights that don't draw extra amps it shouldn't be a real issue.

An alternator isn't going to put out any more amps than a system wants. Most of us go overkill on alternators during swaps and they never put out what they are capable of.

[dsraven]

if going for a new set of aftermarket gauges you might check out some of the posts here on how some guys have used a basic analog volt gauge and placed it in the dash where the original amp gauge was and it functions as a volt meter insetad of the original amp meter. it looks stock but would need to be relabelled. perhaps safer than the amp meter. it would tell you the condition of the system as far as if it is charging and keeping the voltage where it should be. running voltage should be up around 14 or 14.6 volts. more thn that will start to boil the battery. less than that and one would need to know what sort of draw is currently on the go as well as the engine rpm. so, large draw, low rpm maybe thats normal but should jump up to the 14 or 14.6 with a little rpm raise.
anyway, without knowing what you have to work with as far as loads etc all we can do for you is give suggestions as to what to watch for. just remember you are working with OLD stuff.

[ApacheProject]

My truck doesn’t have much, just all factory lights and horn. No radio, heater/AC, power anything. Alternator used is a 63 amp

[dsraven]

thats like the smallest alt you can get these days. you would likely be ok since you don't have much for amp draws. like somebody else said, the stock amp gauge is only really good for what a stock truck would draw with the stock accessories like heater and lights. you would likely get away with the stock amp gauge but realize that IF something goes awry you could smoke the amp gauge AND possibly catch something on fire behind the dash since the gauge is gonna get really hot when it fails. do you plan to run a battery cut off switch by chance? that would be a life saver if you DID have an issue you could shut the truck off and disconnect the battery with the switch. it would have to be in the cab for easy access.
best approach is to try it. get it up and running, park brake on and wheels blocked for safety and then get a helper to turn on accy one circuit at a time while you have your head up behind the dash keeping an eye on the heat produced by the amp gauge. use your sniffer too for any odd smells like something getting hot. the draw rating from the stock gauge is what one big circuit on a newer vehicle is fused for.

[ApacheProject]

I’ll do that, maybe use a laser temp gun to check ammeter before and after turning on the lights while the truck is running. Guess it won’t hurt to start looking into doing it the right way to avoid problems down the road. Funny thing, when I bought this truck years ago the guy was running an alternator with no problems. I don’t remember how he had it hooked up, we tore the truck apart shortly after purchase. There were no extra gauges so he must have run it thru the ammeter. Thanks for everyone’s input and help. Much appreciated

[dsraven]

headlights draw current for sure but the heate rmotor is also another big pull, thats what both circuits use relays on more modern vehicles. the other thing to look at is whether you have a trailer plug circuit. trailers, in general, are not kept up until something breaks so you just never know what the wiring is like or what the current draw will be. best is to start with a current draw on each circuit one at a time. so, running engine, turn lights on and check draw. then lights off and heater motor on high, draw check. then heater and lights off and turn on whatever else you have left, current draw check. then, without turning anything off, turn on the next largest draw, current draw check, then the next largest current draw, etc etc. if you draw more than the old amp gauge is good for then you WILL have trouble at some point.

[leegreen]

OEM generator max output was 25 amps or less, now you have 60 on tap. I'd put a fuse or breaker between alternator and ammeter, probably 30 amp.

[dsraven]

yeah, thats kinda what I was alluding to. probably all good unless you have a draw spike for whatever reason. some sort of circuit protection would be a great idea. just gotta make sure the alternator can still sense battery voltage or it may spike the voltage really high, like those attachments you used to be able to get so you could run an electric drill off your alternator. kinda like fixing a hole in your boat with bubble gum. likely all good unless the bubble gum deteriorates.....maybe screw a fuse onto the alternator output connection, that way it is easily seen, tested or replaced and protects the circuits from there onward.

[leegreen]

To start adding additional loads beyond factory '58 I'd look at getting a multiple pole ignition switch and connecting one set of contacts directly to battery via another suitable sized fuse/breaker. And add a heavy wire from alternator output back to battery if there is not one already.

The factory ammeter will still work and show the load on that factory wiring harness and the volt meter OP mentioned above will show state of charging system overall.
(for $20 on amazon you can get a digital volt & ammeter that uses a clamp style inductive pickup, they are not very 1958 looking but you could hide it in glove box or somewhere)

If the fuse between alt and ammeter blows the engine will stop as the ignition switch 'acc' looses power.
The alternator harness 'should' take the voltage regulation current from the horn or headlight connection shown in original post.

[1project2many]

The original wiring places the battery on one side of the ammeter and the alternator and rest of the vehicle on the other side. The ammeter only measures current flow to and from the battery. Any lights, audio equipment, computer or electronics, or other electrical goodies in the truck should be connected to the vehicle wiring harness. This way the current to power the accessories is not measured by the ammeter.

Two conditions that can cause the ammeter to measure high current are 1) battery failure, and 2) alternator failure. If the battery fails in a way that the alternator believes it needs to deliver full current to produce a charge then the ammeter might not survive. If the alternator fails and there are high current accessories on, the battery is going to try to step up and deliver that current.

In later years GM made the ammeter capable of working with higher current by adding a shunt resistor. The shunt provides an alternate path for current so the ammeter measures a fraction of the actual current to and from the battery. It's possible to find an OE shunt resistor, part no 6473150 is for 67-72 pickups, to add to the back of your ammeter. It's also possible to make an effective shunt using a piece of stainless, a long length of copper wire, or another method. OEM shunt resistors measure about .06 Ohms which is extremely low.