More Drop At Idle With H/O Alt?!?!

[TRTC360]

Well my friend just got this excessive amperage 200 amp alt installed in his mazda 626, with his old alternator at idle he would charge at 14.2-14.4 and now with the new alt he's dropping to 12.8 idle, if he turns the a/c on it jumps up to 13.3 and if he revvs it up it goes up to 14.3 and holds, we hooked up an RD 3250.1 at 1 ohm and at full tilt he was dropping no lower than 13.2 with the engine revved up when with the old alt he was dropping to high 10's, why does he lose so much voltage at idle with the new alt compared to the old one?

[MrSkippyJ]

maybe the RPMs are too low are idle for the alt to have any output?

[Robert8252]

Heard many bad things about excessive amperage. They don't do well at idle.

[TRTC360]

maybe the RPMs are too low are idle for the alt to have any output?

I was thinking it might be an issue with the different sized pulley, but then again why does his voltage go up with the A/C on? my first guess was that maybe this alt doesn't put out power if the current draw isn't there.

[Miguels]

your car must have low idle, when you turn AC on the engine idles a bit more so it turns your alt on. it happens with any brand H/O alts you need to check your idle speed

[MrSkippyJ]

maybe the RPMs are too low are idle for the alt to have any output?

I was thinking it might be an issue with the different sized pulley, but then again why does his voltage go up with the A/C on? my first guess was that maybe this alt doesn't put out power if the current draw isn't there.

usually RPMs go up a bit when A/C is turned on.

totally ninja'd!!!

Edited March 1, 2012 by MrSkippyJ

[Cardboardcat15]

maybe the RPMs are too low are idle for the alt to have any output?

This is the issue with my Mechman alt. When I'm in drive, my engine idles right below the idle turn on speed, so if I'm at a stoplight or stop sign, I get no charge (but why would I need a charge at those places anyway?) Once I rev my engine, RPM"s hop up and boom, I have a charge.

In park however, I've got the RPM's turned up a bit so it idles at the turn on speed of the alt, so in park (when giving Demo's and whatnot) I get charging.

This is the issue with putting big alts on small engines. =/

[Decaf]

its not a bad alt. its not spinning fast enough. did your friend get an Overdrive pulley?

slowing increase RPM til it reads the same 14.3-14.4... what RPM is needed to achieve that?

Edited March 1, 2012 by Decaf

[MrSkippyJ]

maybe the RPMs are too low are idle for the alt to have any output?

This is the issue with my Mechman alt. When I'm in drive, my engine idles right below the idle turn on speed, so if I'm at a stoplight or stop sign, I get no charge (but why would I need a charge at those places anyway?) Once I rev my engine, RPM"s hop up and boom, I have a charge.

In park however, I've got the RPM's turned up a bit so it idles at the turn on speed of the alt, so in park (when giving Demo's and whatnot) I get charging.

This is the issue with putting big alts on small engines. =/

yeah, he told me if I put an alt on my car i would need to adjust the idle RPM to have any output.

[Mario928]

maybe the RPMs are too low are idle for the alt to have any output?

This is the issue with my Mechman alt. When I'm in drive, my engine idles right below the idle turn on speed, so if I'm at a stoplight or stop sign, I get no charge (but why would I need a charge at those places anyway?) Once I rev my engine, RPM"s hop up and boom, I have a charge.

In park however, I've got the RPM's turned up a bit so it idles at the turn on speed of the alt, so in park (when giving Demo's and whatnot) I get charging.

This is the issue with putting big alts on small engines. =/

You are correct. I have the same problem with my alternator. I call Mechman and they told me that i needed to get my rpm up like 800 rpm. I have a 4 cylinder Protege 5. I need to get this issue fix but don't know how to.