I have a delco remy alternator that puts out 61 amp, however I am installing a vintage air kit and probably two electric fans. My local alternator shop said that they could build my current unit to 140 amps.... does this sound right? Also, will this bogg my engine down and is this enough amp to run all the components?

It sounds like you currently have a 10si or 12si alternator. Your local alternator shop is correct, in that they can convert your old alternator to a 140 amp output, but there are issues associated with the conversion. The old 10si case has a restricted air intake area in the rear of the housing for internal cooling, the 12si case has a slightly larger air intake area, but not ideal for 140 amps.

An alternator that generates a large amount of amps is going to generate a lot of heat in the course of outputing that kind of power. The older style 10si and 12si cases, with their restricted air intake opening will somewhat hamper the internal cooling of the alternator diodes and voltage regulator. They will work, but the internal heat will somewhat shorten the overall life of the alternator.

If you need a larger output alternator, which it sounds you will require for the additional electrical components you plan on installing, they make the 12si in a 100 amp version, I believe. Personally, I would opt for the AC Delco CS130 140 amp alternator. It has a larger rear housing air intake area and it has dual cooling fans, one on the outside at the fan pulley and an internal fan at the front of the stator to assist in cooling the alternator.

Even if you install a 140 amp alternator, its not cranking out high amperage all of the time. It will respond to the power requirements as needed. I have a CS130 140 amp on my vehicle, at idle with no real electrical demands, it outputs 8 or 9 amps. Turn on the headlights, it goes to 30 amps, add the AC and it jumps to around 50 amps. Turn any of these off and it drops back down. It only outputs amps as needed.

If you go to a 140 amp alternator, you will need to upgrade you alternator output wire to a 6 or 8 guage wire, depending on the length required.

What price did the local shop quote you for a 140 amp conversion?

Don

You will notice some degree of idle speed decrease with increased electrical load just as you do now. That energy has to come from somewhere. It will only occur when there is high electrical load though. That is also why you should set your idle speed with headlights and heater fan on (or some combination of electical load).

You will see more load variance with the A/C compressor cycling on/off though.

It sounds like you currently have a 10si or 12si alternator. Your local alternator shop is correct, in that they can convert your old alternator to a 140 amp output, but there are issues associated with the conversion. The old 10si case has a restricted air intake area in the rear of the housing for internal cooling, the 12si case has a slightly larger air intake area, but not ideal for 140 amps.

An alternator that generates a large amount of amps is going to generate a lot of heat in the course of outputing that kind of power. The older style 10si and 12si cases, with their restricted air intake opening will somewhat hamper the internal cooling of the alternator diodes and voltage regulator. They will work, but the internal heat will somewhat shorten the overall life of the alternator.

If you need a larger output alternator, which it sounds you will require for the additional electrical components you plan on installing, they make the 12si in a 100 amp version, I believe. Personally, I would opt for the AC Delco CS130 140 amp alternator. It has a larger rear housing air intake area and it has dual cooling fans, one on the outside at the fan pulley and an internal fan at the front of the stator to assist in cooling the alternator.

Even if you install a 140 amp alternator, its not cranking out high amperage all of the time. It will respond to the power requirements as needed. I have a CS130 140 amp on my vehicle, at idle with no real electrical demands, it outputs 8 or 9 amps. Turn on the headlights, it goes to 30 amps, add the AC and it jumps to around 50 amps. Turn any of these off and it drops back down. It only outputs amps as needed.

If you go to a 140 amp alternator, you will need to upgrade you alternator output wire to a 6 or 8 guage wire, depending on the length required.

What price did the local shop quote you for a 140 amp conversion?

Don


They said it would cost 55 to take it to 95 amps and 75 to take it to 140. Do you think I could get away with 95 amps or should I just go all the way?

Thanks for the input.

A 95 amp alternator would probably work, but if for the extra $20, I would probably opt for the 140 amp. The reason being, that the 140 amp alternator will usually put out more amps at idle or lower rpms than a smaller amp alternator will.

Heres an example of what you will see, when you have the Vintage AC going the dual radiator fans should be wired to be running at the same time, so you will have the high amp draw from both the AC compressor and the radiator fans at the same time. Most alternators will not reach their rated amperage output unless you are at a crusing rpm, at which case, the 95 amp alternator would probably be sufficient for your electrical load. When your rpms drop, like idling at a stoplight, your alternators output will be somewhat reduced until you began moving again to make the alternator spin faster. Like Vrooom3440 indicated, at idle you will notice the idle laboring somewhat as the alternator is attempting to output the required amperage. This is where the 140 amp alternator would out perform the lessor 95 amp alternator. The larger amp alternator will output more amperage at lower rpms to try to keep up with the power demand. With the 95 amp alternator this would be more noticable at night, like when you had the AC compressor running, with the dual fans on and with your headlights on, when you came to a stop you would probably see a slight drop in the headlight brightness and then when you began to accelerate again, the headlights would brighten up again as the rpms increased to bring the alternator back up to its higher output range. This would probably be less noticable or nonexistent with the higher output 140 amp alternator.

Assuming your alternator shop does quality work, the prices they quoted you are extremely reasonable!

Don

A 95 amp alternator would probably work, but if for the extra $20, I would probably opt for the 140 amp. The reason being, that the 140 amp alternator will usually put out more amps at idle or lower rpms than a smaller amp alternator will.

Heres an example of what you will see, when you have the Vintage AC going the dual radiator fans should be wired to be running at the same time, so you will have the high amp draw from both the AC compressor and the radiator fans at the same time. Most alternators will not reach their rated amperage output unless you are at a crusing rpm, at which case, the 95 amp alternator would probably be sufficient for your electrical load. When your rpms drop, like idling at a stoplight, your alternators output will be somewhat reduced until you began moving again to make the alternator spin faster. Like Vrooom3440 indicated, at idle you will notice the idle laboring somewhat as the alternator is attempting to output the required amperage. This is where the 140 amp alternator would out perform the lessor 95 amp alternator. The larger amp alternator will output more amperage at lower rpms to try to keep up with the power demand. With the 95 amp alternator this would be more noticable at night, like when you had the AC compressor running, with the dual fans on and with your headlights on, when you came to a stop you would probably see a slight drop in the headlight brightness and then when you began to accelerate again, the headlights would brighten up again as the rpms increased to bring the alternator back up to its higher output range. This would probably be less noticable or nonexistent with the higher output 140 amp alternator.

Assuming your alternator shop does quality work, the prices they quoted you are extremely reasonable!

Don


thanks for the information... I thought the prices sounded reasonable too. think I will probably ge the larger amps, so I will have plenty of power later down the road.

When I did my upgrade to twin fans I also needed to upgrade my alt. I carried it to a friend at his shop, and told him what I was going to do. He rebuilt my alt to 110amp. I stayed with the ext reg, and had to order a larger reg. I also upgraded the wiring. My friend charged me $60.00 for the rebuild. It has worked well, with all my additional applications, my sons amp addition in the trunk, CD player etc. The alt has done the job well, ( I wired both fans to come on at the same time. Even in the summer it runs 185-187 all the time. Check out my showroom.