Alternator / Voltage Regulator

[patrickt]

I added up my amperage loads on my car. With every single switch I have turned on I'm still only in the 40's. The only way I can test that circuit breaker would be to bench test it or short it out... so I'll just leave it be.

[davids2toys]

Originally Posted by patrickt

I added up my amperage loads on my car. With every single switch I have turned on I'm still only in the 40's. The only way I can test that circuit breaker would be to bench test it or short it out... so I'll just leave it be.

Would the car running or not be in your calculations? Wouldn't that be part of you stuff that would be using juice?

[patrickt]

Originally Posted by davids2toys

Would the car running or not be in your calculations? Wouldn't that be part of you stuff that would be using juice?

That's with the engine off. Of course, if the engine is running, then your alternator is feeding the loads and it's not running through the circuit breaker. And I checked the fan load with the engine cold. When the engine is HOT, the fans draw more current.

[davids2toys]

Originally Posted by patrickt

That's with the engine off. Of course, if the engine is running, then your alternator is feeding the loads and it's not running through the circuit breaker. And I checked the fan load with the engine cold. When the engine is HOT, the fans draw more current.

Never occurred to me? So that CB is only handling juice when the car is not running.
I should have paid more attention in auto shop!
OK, going out on a limb here. So your MSD box wire in not protected it if the car is running because you have it hook up to the protected side of the CB.
Why is the CB there then? What is protecting this when the car is running, the glass fuses?

[DanEC]

I bought a braided ground strap to install from my transmission to the frame from McMasters. Their selection was not real extensive but I found something to work. It had ends made up on it.

[patrickt]

Originally Posted by davids2toys

So your MSD box wire is not protected if the car is running because you have it hook up to the protected side of the CB.
Why is the CB there then? What is protecting this when the car is running, the glass fuses?

The car will not be running if: 1) the MSD box shorts out (which will blow the internal 15 amp fuse on the MSD circuit board) or 2) the feed wire to the MSD box shorts out (because the box itself will no longer be fed. If the MSD feed wire shorts out, or if the line that leads to the ammeter shorts out, the circuit breaker will blow because the battery will try and pump lots of amps through that line even if the alternator is still turning. The glass fuses protect shorts on the load side, for the most part. Remember, almost all of the wires in your car, even the skinny little wires, will handle 50 amps for a short while <pun>. and the CB will blow if the battery dumps more than that. One of the most common wiring fires is the result of a short in the line between the alternator and the battery (the one with the ammeter in between). If this line shorts out, the CB will blow, but the alternator will still pump out its maximum for a while, and that's where the fire comes from. Now, my alternator only puts out 60 amps, so the location of the fault will spark and smoke, and maybe some plastic nearby might catch, but the wire itself can carry 60 amps with no trouble. Some of the bigger alternators are a different story.

[davids2toys]

Originally Posted by patrickt

The car will not be running if: 1) the MSD box shorts out (which will blow the internal 15 amp fuse on the MSD circuit board) or 2) the feed wire to the MSD box shorts out (because the box itself will no longer be fed. If the MSD feed wire shorts out, or if the line that leads to the ammeter shorts out, the circuit breaker will blow because the battery will try and pump lots of amps through that line even if the alternator is still turning. The glass fuses protect shorts on the load side, for the most part. Remember, almost all of the wires in your car, even the skinny little wires, will handle 50 amps for a short while <pun>. and the CB will blow if the battery dumps more than that. One of the most common wiring fires is the result of a short in the line between the alternator and the battery (the one with the ammeter in between). If this line shorts out, the CB will blow, but the alternator will still pump out its maximum for a while, and that's where the fire comes from. Now, my alternator only puts out 60 amps, so the location of the fault will spark and smoke, and maybe some plastic nearby might catch, but the wire itself can carry 60 amps with no trouble. Some of the bigger alternators are a different story.

Thanks Pat. I think I actually understand what you are saying here!!
Is there a way to tell how big of an Alt you have? I know I have an external regulator and that is about it.
Dave

[patrickt]

Originally Posted by davids2toys

Thanks Pat. I think I actually understand what you are saying here!!
Is there a way to tell how big of an Alt you have? I know I have an external regulator and that is about it.
Dave

There are two ways to tell. The hard way is to remove it and test it for maximum output current. The easy way is to look for the plate that is attached to the outside of the housing. Manufacturers of alternators conspire to always place the plate in such a way so as to make it as difficult as possible to see while just peering in to the engine bay. Stick your phone down under the alternator and snap a few pics from beneath. Then Google the model number of the alternator and it will give you the specs.

[davids2toys]

Originally Posted by patrickt

I added up my amperage loads on my car. With every single switch I have turned on I'm still only in the 40's. The only way I can test that circuit breaker would be to bench test it or short it out... so I'll just leave it be.

Maybe I'm way off here, but couldn't you use that clamp meter to measure your Real/actual amperage going thru the CB?

[patrickt]

Originally Posted by davids2toys

Maybe I'm way off here, but couldn't you use that clamp meter to measure your Real/actual amperage going thru the CB?

Yes, with the engine off and everything turned on that would give an exact reading on the total amperage. It was just easier to add it all up in my head than to walk downstairs to the garage and actually measure it. Since all my lights are LEDs, which account for very little current, my fans and head lights are pretty much it. Of more interest is the amp draw by the fans. If you look at your SPAL data sheet, it has a nice little table that shows the different current draws based on the temperature and whether you have it as a pusher or puller. When I shut down my engine, and it is nice and hot, the current draw, as measured, is five amps or so more than when the engine is cool. Of course, the voltage is a little lower too since the alternator is not running.

[davids2toys]

Originally Posted by patrickt

Yes, with the engine off and everything turned on that would give an exact reading on the total amperage. It was just easier to add it all up in my head than to walk downstairs to the garage and actually measure it. Since all my lights are LEDs, which account for very little current, my fans and head lights are pretty much it. Of more interest is the amp draw by the fans. If you look at your SPAL data sheet, it has a nice little table that shows the different current draws based on the temperature and whether you have it as a pusher or puller. When I shut down my engine, and it is nice and hot, the current draw, as measured, is five amps or so more than when the engine is cool. Of course, the voltage is a little lower too since the alternator is not running.

I borrowed a friend's amp tool See post #45 Bad Starter
Car OFF and cold, with the fan, high beams, and wipers on I got about 15 amps going thru the CB. Seems pretty good to me?
No brake lights, horn or blinkers.
I might have to do this again. It is after midnight and I'm beat. Maybe I screwed this up...LOL

[patrickt]

Originally Posted by davids2toys

Maybe I screwed this up...LOL

You did. There's no way that's only pulling 15 amps. If you take your headlights alone, two 60 watt bulbs is 120 watts, divide that by 12.6 volts, and you get 9.5 amps for the lights alone. I'll look at your other post on "Bad Starter" to see if I can see what you're doing wrong.

[davids2toys]

Originally Posted by patrickt

You did. There's no way that's only pulling 15 amps. If you take your headlights alone, two 60 watt bulbs is 120 watts, divide that by 12.6 volts, and you get 9.5 amps for the lights alone. I'll look at your other post on "Bad Starter" to see if I can see what you're doing wrong.

You're right, it was either the gauge or me. I went out and re-did it this morning and it was not 15, it was 5 amps. when I saw that, I tried it on the 10 amp scale and it gave me about 2 amps. I canned the whole idea with this gauge. I went to Sears today and bought the clamp gauge you suggested. I will try again Friday or Sat. I am just putting the probe on both sides of the CB. Speaking of the CB, I got the new one today(type 3). What a cheap looking piece of crap compared to the metal auto resetting Type 1 that is in the car now. Last week I tested the resistance in the old CB and it read zero or .01ohms, I forgot. I will do the same to this new one and see what I get.
Just went out and checked it. It flashes a number for a split second and goes to 0.000 immediately. The number looks to be .750 most of the time before it flashes to zero. When I say split second I mean it. does this sound right?
In testing the CB I just went from stud to stud and disconnected no wires. . I guess my thinking was I just wanted to see what was running thru the breaker. Maybe that is why the very low reading. Please enlighten me on the Patrick procedure correct way to do this test...LOL
Dave

[patrickt]

Originally Posted by davids2toys

In testing the CB I just went from stud to stud and disconnected no wires. I guess my thinking was I just wanted to see what was running thru the breaker. Maybe that is why the very low reading. Please enlighten me on the Patrick procedure correct way to do this test...LOL
Dave

Naaah, you're wasting your time doing it that way -- and you're only going to fool yourself with the results. Measuring resistance will only get you so far. For example, let's say you have two wires, one is a nice new fat 0 gauge battery cable and the other is a ratty old piece of copper strand the thickness of a dog hair. You get out your trusty multimeter and you check the resistance on both wires and they both show just about no resistance. Maybe the dog hair is actually a little less in ohms, who knows. What does the test tell you? Nothing. The moment you put a load on the dog hair the wire will go *poof* and you'll have an open circuit. In order to really measure a "thing" that is on an automotive circuit, be it a span of wire, a circuit breaker, a fuse, a connection, etc., you must perform a "voltage drop test." That's your next lesson after you master clamping your inductive amp meter around a wire.