[71 Chevy]

Guys,thanks for helping me with the alternator problems. I have an unsolved one.

I'm only getting 13.6v max at both voltmeters.this is from 7000 to 2400 rpms tested so far

Is the 12si regulator adjustable?
Could it be because I have some things running from the battery as opposed to the main junction?
I have electric fuel pump,megasquirt ecu,and ignition coming straight off the battery will the sensing wire to the alternator be able to see these loads?

If not,do I need to move them to the main junction?

Thanks guys

 

[The Big Al]

Could it be because I have some things running


Thanks guys

you just answered you own question.

alternator means just that!

Alternator! Alternating voltage current as needed.

Al

 

[71 Chevy]

you just answered you own question.

alternator means just that!

Alternator! Alternating voltage current as needed.

Al

sorry big al I dont get it what you are saying?

 

[Nova_Guy]

you just answered you own question.

alternator means just that!

Alternator! Alternating voltage current as needed.

Al

You have lost me too Al. The alternator as far as I know makes AC current that is switch over to DC via the diode triode. The diodes only pass the + side of the AC wave form to make DC voltage. The regulator inside the the alternator regulates the amount of current and voltage. It's been a long time since tech school.

http://www.alternatorparts.com/understanding_alternators.htm

 

[71 Chevy]

You have lost me too Al. The alternator as far as I know makes AC current that is switch over to DC via the diode triode. The diodes only pass the + side of the AC wave form to make DC voltage. The regulator inside the the alternator regulates the amount of current and voltage. It's been a long time since tech school.

http://www.alternatorparts.com/understanding_alternators.htm

your link also brought up another thing. the alternator warning light does not light up even though voltage is only 13.6 . is this normal?

 

[The Big Al]

From my poor understanding of the vehicle charging system!!!!

the alternator reacts to load and battery.

Is this not correct?



From the specs!

The actual output voltage produced by the charging system will vary depending on temperature and load, but will typically be about 1-1/2 to 2 volts higher than battery voltage. At idle, most charging systems will produce 13.2 to 15.3 volts with no lights or accessories on. This can be measured by connecting the positive (+) and negative (-) test leads of a voltmeter to the battery posts while the engine is running.

 

[Philip]

From the specs!

The actual output voltage produced by the charging system will vary depending on temperature and load, but will typically be about 1-1/2 to 2 volts higher than battery voltage. At idle, most charging systems will produce 13.2 to 15.3 volts with no lights or accessories on. This can be measured by connecting the positive (+) and negative (-) test leads of a voltmeter to the battery posts while the engine is running.

Right on the money, check for the voltage difference between key off and engine running. If within this spec it is fine, if not than just the regulator could be changed since the alternator is obviously working.
The dash light should only be on if the output of the alternator is less than battery voltage, hence a discharge condition while running, not based on a specific voltage reading.

 

[71 Chevy]

ok, the battery is on the charger right now. will try it again when its fully charged. the voltmeter is reading 11 volts with the key on but engine not running

but, I thought the job of an alternator was to supply the car with a specified voltage level. ie , 14.2 volts regardless of load or battery charge. is this wrong?

 

[Philip]

14.2 is the ideal that the system is designed to deliver but that is with a fully charged battery and fully charged 12 volt battery is about 12.8 - 13.2 volts. When charging a battery the slower the charge the better it will bring the battery to full charge. A lot of chargers put a surface charge on the battery that is quickly depleted. This is fine to get it up quickly and then let the alternator top it off slowly. I use a 1 amp charger and it will sometimes take 30 hours to bring one up to full charge, but if the battery is good it will hold that charge a long time.

 

[Custom Jim]

I thought the job of an alternator was to supply the car with a specified voltage level. ie , 14.2 volts regardless of load or battery charge. is this wrong?

An alternator will supply a particular voltage at a particular RPM.

Different alternators and setups can output 13.2 volts, 13.5 volts, 14.2 volts and plenty of other voltages.

Some regulators are set to have the alternator output 13.2 volts, 13.5 volts, 14.2 volts and plenty of other voltages.

I have an older high output alternator on my 73 and it came with an adjustable external regulator. With 1/0 wire off of the output post of the alternator going back to my trunk mounted batteries positive post (and through a relay and fuse) and a 1/0 wire off of the alternators case run back to the batteries negative terminal I was able to dial in 14.4 volts right across the battery terminals. I've never measured the output voltage right at the alternators output post and the alternator case but I'm pretty sure it would read close to 15 volts. The reduction of voltage back at my batteries is due to cabling length and connections.

On my car at idle the indash Dakota digital volt gauge will read anywhere from 13.6 volts or so and once the engine is above idle (let's say 1500 RPM) the voltage goes up to 14.4 volts. If I let the nominal voltage of the battery go down by playing the stereo with the engine off I only like to let the battery voltage drop to about 11 volts or so, so I can then still start the car and recharge the battery but now it takes 20-30 miles of driving before the voltage reading I see in the dash gauge is back at 14.4 volts.

The reasons I have this adjustable regulator on my 73 is the adding charging wires due to the trunk mounted battery and years ago I was limited to only inputting 14.4 volts into the car stereo's amplifier system. I knew there were going to be voltage drops through the cabling even though it is oversized and I would also have voltage drops through connections.

I've had cars with readings of a little over 13 volts to ones with 14 volts. With these cars, if the system was right, I never had battery or charging problems.

Another thing to throw out is if you have a 100A output alternator running at a slow armature speed it may only be able to output 50A and if you are drawing 60A with things off of the system, 10A is coming off of the battery and the volt gauge will slowly read lower and lower as the alternator cannot keep up. Slow alternator armature speeds reduce voltage and amperage output.

Jim

 

[tnblkc230wz]

People also fail to factor in voltage drops. Measuring voltage at the battery tells you the voltage at that point in the system. The voltage at that point depends on several factors including the wire temps, length of the wire runs, the size of the wire runs and electrial load. They all conspire to lower the voltage.

13.6 volts at the battery is pretty good, especially if there is any load on the system. Your idiot light will not come on at 13.6 volts because the altenator is working. If you really want to know how much voltage your altenator is putting out, you have to measure at the back of the altenator or at the end of the sensing wire. These two locations will not have voltage drops caused by the factors listed above.

 

[6NOVA4]

An alternator will supply a particular voltage at a particular RPM.

Different alternators and setups can output 13.2 volts, 13.5 volts, 14.2 volts and plenty of other voltages.

Some regulators are set to have the alternator output 13.2 volts, 13.5 volts, 14.2 volts and plenty of other voltages.

I have an older high output alternator on my 73 and it came with an adjustable external regulator. With 1/0 wire off of the output post of the alternator going back to my trunk mounted batteries positive post (and through a relay and fuse) and a 1/0 wire off of the alternators case run back to the batteries negative terminal I was able to dial in 14.4 volts right across the battery terminals. I've never measured the output voltage right at the alternators output post and the alternator case but I'm pretty sure it would read close to 15 volts. The reduction of voltage back at my batteries is due to cabling length and connections.

On my car at idle the indash Dakota digital volt gauge will read anywhere from 13.6 volts or so and once the engine is above idle (let's say 1500 RPM) the voltage goes up to 14.4 volts. If I let the nominal voltage of the battery go down by playing the stereo with the engine off I only like to let the battery voltage drop to about 11 volts or so, so I can then still start the car and recharge the battery but now it takes 20-30 miles of driving before the voltage reading I see in the dash gauge is back at 14.4 volts.

The reasons I have this adjustable regulator on my 73 is the adding charging wires due to the trunk mounted battery and years ago I was limited to only inputting 14.4 volts into the car stereo's amplifier system. I knew there were going to be voltage drops through the cabling even though it is oversized and I would also have voltage drops through connections.

I've had cars with readings of a little over 13 volts to ones with 14 volts. With these cars, if the system was right, I never had battery or charging problems.

Another thing to throw out is if you have a 100A output alternator running at a slow armature speed it may only be able to output 50A and if you are drawing 60A with things off of the system, 10A is coming off of the battery and the volt gauge will slowly read lower and lower as the alternator cannot keep up. Slow alternator armature speeds reduce voltage and amperage output.

Jim

would it be possible to see some pics of your wiring? isn't 1/0 wire welding cable?

 

[Custom Jim]

would it be possible to see some pics of your wiring? isn't 1/0 wire welding cable?

Look around in webshots.com under user name Custom_Jim and there should be some shots of my 73. Probably not a lot of the wiring but if you do find a shot of the engine from the passenger side down towards the headers, the braided line in that area houses the 1/0 wires I have off of the alternator. I used my old braided heater hose lines to encase the 1/0 wire and I think on the ends I used the style of braided line ends that had the worm clamps inside of them but I removed the clamp and modified the rest of the end to where I didn't have the loose ends of the braided line being exposed.

1/0 wire could be considered welding cable, main feed wire, tow cable, and a lot of other things. It's been years since I wired my 73 and I used Esoteric brand wire power and ground 1/0 wire (and back when it was maybe a buck a foot ?). 1/0 is a wire size and the size of wire could be made up of a few large stands of wire or a lot more smaller strands. A large amount of smaller wires will allow the cable to flex easier than a small amount of larger wires. Back in the late 70's I did use some old welding cable but the problem I had with it was the internal wires were corroded and I was unable to solde the terminal ends onto it. With the new wire I bought I was able to solder on the ends after crimping them onto the wire.

Something interesting was I put mine into the braided line to help protect it from being pinched and act as a heat barrier but I saw in a trade magazine a new insulation being used on wire that they showed a flame up against it off of a small torch and the insulation was staying intact and not melting. I wonder if something like this will make it's way into the automotive industry. I wonder too how flexible it might be.

Jim