(3g swap done)Which wire to test alternator amps?

[Marlboro_Man]

Ok i just finished my 3 g alternator swap and it went pretty smooth except i don't know where to put my amprobe (which wire) to see how many amps it's putting out. It did seem to idle a little rough when i first started it up , but it seemed to smoth out a little after a few minutes.

So question is which wire do i put my amprobe around to see how many amps it is putting out?

Also does anybody know if the alternator bracket from a 90's model f series truck is the same as ours? Cause when i was tightening up the bottom bolt the bracket cracked, but i have 3 90's model f150's at my shop i can use for parts.


Thanks ahead, Matt
:SNSign:

 

[Skoobie]

Test it at the battery terminals while the car is running. If your above 14.0 your doing great!

 

[Marlboro_Man]

Test it at the battery terminals while the car is running. If your above 14.0 your doing great!

Ok if i test the voltage (dc) at the battery terminals i get mostly 14.2-14.8 but it does jump up a little sometimes to 18 volts dc.

But to my original question , where do i check to see how many amps the new alternator is putting out?


Matt

 

[Michael Yount]

Skoobie - he wants to measure AMPS not VOLTS.

MM - alternators don't work the way you think they do. The current is DRAWN from them -- they don't just put out at the nominal rating. The 130A units are capable of putting out something around 90A at idle up to around 180A at higher rpm. The 130 rating is nominal. To test output, you need to run by a Sears or AutoZone - somewhere where they have an alternator LOAD TESTER -- most of them use induction to place a load on the alternator to see what it can put out. You'll have a hard time simulating that in your driveway -- although I suppose you could turn every accessory you have on at it's highest setting...

 

[Marlboro_Man]

Skoobie - he wants to measure AMPS not VOLTS.

MM - alternators don't work the way you think they do. The current is DRAWN from them -- they don't just put out at the nominal rating. The 130A units are capable of putting out something around 90A at idle up to around 180A at higher rpm. The 130 rating is nominal. To test output, you need to run by a Sears or AutoZone - somewhere where they have an alternator LOAD TESTER -- most of them use induction to place a load on the alternator to see what it can put out. You'll have a hard time simulating that in your driveway -- although I suppose you could turn every accessory you have on at it's highest setting...

Thanks for the quick replies!

Ok well on this link below they installed a 3g w/the PAperformance kit on a 93 and then they show video of them testing the voltage and amps, after watching the video closely it shows them putting their clamp meter on the 4 awg wire off the back of the alternator and thats where they are checking the amps from. Thats where i thought i should test from also , but with my Fluke digital meter with the clamp on i checked there for amps and i only get like 2-5 amps but maybe i just had my meter on the wrong setting or something.

Matt
http://www.fordmuscle.com/archives/2001/03/paperformance/index1.shtml

 

[Skoobie]

Yes yes my bad amnit: From what I know though the best way to test out a succesful install/working alt is to test the volts at the terminals. If your running 14.2-14.8 things should be golden.

 

[Michael Yount]

MM - that 'clamp' is an inductive lead -- that's HOW they load the alternator. You can't really test amperage without loading the alternator.

 

[Marlboro_Man]

Well now that makes sense lol.

Well idleing at about 900-1000 i'm getting 13.7 volts at the terminals and about 13.2 with the headlights and all the accessories running. Would it be better to put my old 2g pulley (smaller) on the 3g alternator? If so how the hell do you take those things off?

And also if anyone knows whether or not the alt bracket from the 90's model f150 w/5.0 is the same as a fox that would definatly help me out.

Thanks michael for your help

Matt

 

[jrichker]

The 2G had an allen wrench hole in the center of the shaft. Use that & a 15/16" wrench on the nut.

If you have access to an impact wrench, use that with the 15/16" socket & it spins off pretty easily.

 

[Michael Yount]

The 130 ought to handle the load without any problems. You can try the smaller pulley if you like....

 

[HISSIN50]

It is worth asking what your idle setting is when it goes funky. On my true 3G, if the idle is at ~600 RPM, the output drops with a big load. But simply upping it to 700 RPM will bump the output significantly.

You mentioned a miss or rough running, which made me wonder...........

Good luck.

 

[Marlboro_Man]

The miss/rough idle only happened that first time i started it up after the install.

My idle is around 850-1000 rpms , I'm going to have a friend help me this weekend do some tuning with the timing and fuel and also have him help me set the tps and idle.

So everyone knows, The alternator bracket from the 90's model f150 with 5.0 is the same as a fox. I installed one today on my car , however the belt tensioner is not the same so you will have to reuse the one from your fox. I had to dremmel out the threads on the f150 alt bracket where the tensioner bolts up and use a bolt on it.


Matt