ALT?

[SMOKEDYA]

Ok i have the 3g upgrade done.When i'm idoling with the electric fan on and the headlights my amps drop alot.If i'm just idoling with the fan on no lights it's fine.I have the stock gauge.Could the alt be going bad?As soon as i get moving again the amp gauge goes right back to normal. peace











john

 

[k4mjk]

do you have under drive pulleys?

 

[SMOKEDYA]

Yes but it started doing this after i stoped using the black majic fan and switched to this dual set up.peace












john

 

[87GT Drop Top]

I had the same problem. It didn't get fixed until I put the stock crank pulley back on.

 

[SMOKEDYA]

I was thinking of getting a stock crank,water pump and alt pulley.I can't see it raping that much power since all i have is those 3 powered off the motor. peace







john

 

[Mustang5L5]

Either put the stock alt pulley back on, or put an ASP overdrive alt pulley on.

The prob is the alt doesn't generate enough power at idle with the U/D pulleys. Either try to fix it with smaller diameter alt pulleys...or you will have to ditch the U/D's completely

 

[87GT Drop Top]

I tried fixing mine woth a 1 7/8" alt pulley. It got better, but still wasn't right until I put the stock crank pulley back on.

 

[HISSIN50]

First get a DMM on the system so you know what is actually going on. Then make decisions.

When it bogs down with a full load, if you press the gas to raise the idle by about 200-300 RPM and the voltage kicks up, then the pulley scenario sounds like a good place to start.

Just remember that 3G's dont like being spun over 15K RPM.

Good luck.

 

[7upstang91]

First get a DMM on the system so you know what is actually going on. Then make decisions.

When it bogs down with a full load, if you press the gas to raise the idle by about 200-300 RPM and the voltage kicks up, then the pulley scenario sounds like a good place to start.

Just remember that 3G's dont like being spun over 15K RPM.

Good luck.

How much do they spin(or supposed to spin at idle)? I have the same problem, just looking for answers.

 

[Mustang5L5]

If you have your crank and alt pulley diameters, you can do simple math to figure it out.

I forget the number for full charge. I've seen it before. I wanna say 1500RPM for 14+V output, but it's beena while i could be way off

 

[SMOKEDYA]

DMM= digital multi meter? if not what is it? I'm bad at abreviations!Just like the lloc or iirc?I had to go today to replace the coupes alt also,the dam thing f'd up and the wires were smooookin!Good thing for life time warrenty!peace













john

 

[Mustang5L5]

Yup. Digital Multi Meter.

Radio shack makes a half-decent meter for under $20 that i use for quick checks like this. Not very good for much other than voltage..but that's usually what most people need. Closes up nice and fits in the toolbox of glovebox easy

Of course a lot of the cheap meters don't allow measuring amps in DC current which i consider important when working on cars. But for that, i have a nice expensive DMM from the days when i was an electrician and my life would sometimes depend on my meter.

 

[SMOKEDYA]

Ok i have one of those! So care to share what to touch to check it?Just a ground and the positive off the alt that goes to the battery? What should my reading be? What, are you affraid of getting shocked ? I hate that standing on dry ground or water and the welder at work letting me know it's hot or welding and arms touch the table while i'm pipe welding peace



john

 

[Mustang5L5]

Set it to Volts DC. Touch red to either the battery POS, the solenoid POS, or the POS post on the backside of the alt...and touch the black to the NEG on the battery or a good solid chassis ground.

You want to see at least 12V at idle...not ideal, but you aren't discharging. 11V would be a slightly discharging. I beleive 13V is a good number to shoot for at idle and 14.4V should be what you see at any RPM above idle.

 

[HISSIN50]

How much do they spin(or supposed to spin at idle)? I have the same problem, just looking for answers.

I don't understand. They're in the 2500 alternator-RPM range at idle.

The 15K warning was in case the alternator gets an overdrive pulley. Most alternators will have decent output by 1200 engine-RPM.

 

[SMOKEDYA]

Set it to Volts DC. Touch red to either the battery POS, the solenoid POS, or the POS post on the backside of the alt...and touch the black to the NEG on the battery or a good solid chassis ground.

You want to see at least 12V at idle...not ideal, but you aren't discharging. 11V would be a slightly discharging. I beleive 13V is a good number to shoot for at idle and 14.4V should be what you see at any RPM above idle.

ok cool i'll check it tomorrow,i'm sure i'm good at idol and lights on.but with fan and lights on at idol i doubt it?peace




john

 

[7upstang91]

I don't understand. They're in the 2500 alternator-RPM range at idle.

The 15K warning was in case the alternator gets an overdrive pulley. Most alternators will have decent output by 1200 engine-RPM.

Okay Gotcha thanks. I wasn't sure, sounds like I have plently of room. I have the 3G.