Need help with high output alternators.

[adio25 10+ year member]

Alright I have a 2002 Ford Taurus that has PCM controlled 4G alternator with a Diehard platium 100ah and a C&D Tech 93 ah batteries. So here's comes the story.

My first alternator was a powerbastards 220A. It put out next to nothing at idle and would drop my system down to 12.0v. When I would accelerate from idle it would spike the voltage to 15.5v+ for a split second and then go back down to a steady 14.2v. Also, if I would roll all my windows up at once the voltage would drop down from 14.2v to like 14v but as soon as I would stop, my voltage would spike up to like 14.8v back down to the constant 14.2v. These spikes eventually resulted in killing one of my HID bulbs and me sending back the alternator.

I then had my stock alternator rebuilt as a high output. It too had the same low output at idle but it didn't have the voltage spikes when accelerating from idle. At cruise it was great but the low idle voltage resulted in me returning that one also.

I now have a Mechman 240A and initially I got no output of it at all but a simple shorter belt change fixed that. I now get 14.4-14.7v at crusing speed but at idle my voltage dips down to like 12.8v-13v not as bad my older ones but still not acceptable. My stock alternator would always hold 14v+ at idle. I clamped it with my meter and got about 53 amps at a 650 rpm idle in park. When I put it in drive it goes even lower. Also, similar to my initial powerbastards alternator, it does the same 15.5+v voltage spikes when accelerating from idle. Another thing is that my voltage drop when I'm blasting seems to be similar to the voltage drops I saw with my stock alternator. I would expect to atleast stay in the 14's at full tilt when starting from 14.7v. Right now I've seen as low as 13.2v drops before my clipping light comes on.

My main concerns are the voltage spikes screwing up my HID's again and figuring out how to raise the idle output. What could possibly be causing the voltage spikes? A bad regulator? Belt? And would an even shorter belt help with the idle output? The belt tension is within spec according to the tensioner tension indicators.

Any help would be great guys. Thanks

Here's a thread on a Taurus forum I made that might have a little more background info

Mechman Alternator - No output - Taurus Car Club of America : Ford Taurus Forum

Click to read more...

 

[mylows10 5,000+ posts]

Could be a bad rectifier or even the wrong alt all together. Just because it fits. Doesn't mean it right

 

[adio25 10+ year member]

SKU numbers all matched up to what they have on their site but I guess it is possible I did get the wrong alt.. I know the previous generation Taurus didn't have a PCM controlled alternator. Would that type of alternator even match the plug for a PCM controlled alternator like mine?

 

[mylows10 5,000+ posts]

It could. But the PCM just makes the alt run at a lower voltage when needed. An external regulator can resolve that issue on some alts tho

 

[adio25 10+ year member]

No one else??

 

[NASTY08IMPALA 5,000+ posts]

No one else??

Most pcm controlled alts need to be externally regulated to maintain steady voltage ...until I got my externally regulated mechman my voltage would go from 14.8 to 12.9 when kicked into econ mode or 3cyl mode

 

[bbeljefe]

You're okay with the clipping light coming on?

 

[NASTY08IMPALA 5,000+ posts]

Also I run the same amp as you and I run a duracell agm under the hood and 2 100ah dekas in the back with 4 runs of 1/0 and dbl big 3..I drop to 14.2 with the alt fully engaged around 1800-2000rpms but at idle after a while it drops to 13.2 ..I run the mechman 240 also . The reality if it is unless ur running these big 350-370a alt ur niitgoing to get a ton of output at idle

 

[adio25 10+ year member]

The idle voltage I can handle, it's just the spikes to 16v accelerating form idle that scare me the most. HID's will be roasted in no time. And while at 2500 rpm I still drop as much as my stock alternator. **** car audio

 

[Lowflyin 10+ year member]

Also I run the same amp as you and I run a duracell agm under the hood and 2 100ah dekas in the back with 4 runs of 1/0 and dbl big 3..I drop to 14.2 with the alt fully engaged around 1800-2000rpms but at idle after a while it drops to 13.2 ..I run the mechman 240 also . The reality if it is unless ur running these big 350-370a alt ur niitgoing to get a ton of output at idle

It's usually the bigger alts that don't put out as much at idle //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[Dub7sonoma Premium Member]

Changing the belt length has nothing to do with alternator output, unless its too long and its slipping. To increase the output you have to change to a smaller diameter pulley on the alternator. And alternators don't put out full current (amps) at all times. So clamping it wont give an accurate output unless you have a good load on the alternator. Let you car idle and turn the stereo up till your voltages are dropping, not to a dangerous level, but around 12.5v and then clamp it. That should give a better reading of the output at idle.

 

[NASTY08IMPALA 5,000+ posts]

It's usually the bigger alts that don't put out as much at idle //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

Actually most the bigger ones ive see do close to 200 idk where u got that from

 

[NASTY08IMPALA 5,000+ posts]

I kno my mechman 240 does 140 @idle....u need to put the stock alt back on and order a ext regulator before u fry ur car

 

[adio25 10+ year member]

Changing the belt length has nothing to do with alternator output, unless its too long and its slipping. To increase the output you have to change to a smaller diameter pulley on the alternator. And alternators don't put out full current (amps) at all times. So clamping it wont give an accurate output unless you have a good load on the alternator. Let you car idle and turn the stereo up till your voltages are dropping, not to a dangerous level, but around 12.5v and then clamp it. That should give a better reading of the output at idle.

That's exactly what I did and got 53 amps

 

[Dub7sonoma Premium Member]

That's exactly what I did and got 53 amps

Ok cool. Since the alt is a mechman it probably already has an undersized pulley on it. Measure the pulley (in mm) and call mechman to see if they sell a smaller pulley. That's about the only way to boost idle output. But I would focus more on the voltage spikes.