how to pinpoint electrical drop issues?

[ncc74656 2]

so my friend picked up a mechman 220 for his dodge avenger 2012. with his factory alternator he had some decent dimming of lights and gauges even when cruising down the road. with his mechman he says his voltage will drop to 11.2V on the alternator stud and his car has shut off and restarted itself during idle with the mechman but never with his factory alt. he used an amp meter to find out he has about 65A at idle coming from the alt under load. first off how accurate is that measurement? secondly what steps should one take to isolate the alternator vs a ground or other issue in the system?

his system power is about 2KW with a JL 5 channel powering rainbow door components and a phenix gold 1200W on 2 xtant 10" subs.

My mechman seems to work great for me but he is very unsatisfied and I want to do what I can to help him fix it.

how much power would you expect out of any HO alt at idle on a car like that?

[Randal Johnson 544]

Is there a second battery near the amplifiers ?

First thing I woud do is reinstall the origional Alternator and verify all ground locations are good and see if the problem goes away since that's the only thing (from what you are telling us) that has been done to the vehicle.

[ncc74656 2]

there is not a second battery, it is the factory battery up front. yes the alternator swap is the only change that I am aware of to the system.

[Randal Johnson 544]

Might be a better idea to install a second battery near the amplifiers before installing a stronger alternator.

 

 

just a suggestion yo

[ssh 924]

Alternators need to reach a certain rpm before they turn on and produce any current. Some high output alternator designs make lots of current at high rpm but at the expense of current at low rpm. I'm presuming since his car is new it idles pretty low--low enough that it either doesn't trip the alternator turn on speed (so the alt is off) or the alt just makes less power at idle than the OEM alt. To overcome the former people often swap out alternator pulley size so the alt rpm increases enough at idle to meet the required turn on speed, but then you have to worry about spinning the alternator too much at higher engine rpm. IIRC there's a few people on this forum that had Mechman alts and ran into this exact issue.

[ncc74656 2]

I was recommending he install a group 31 diehard platinum marine battery in the trunk. has bolt on stud terminals already and is rather cheap online. 

[ncc74656 2]

I was on the phone with mechman for about an hour during his order. we got the smallest pully that was safe for his car and the 220 should be the alt that is able to produce decent power at high and low RPM's. I have the alt that sacrifices power at low RPM and provides max power only when spooled to the upper ranges. his alt should produce considerably more power than mine does at idle. difference is I drive a diesel that red lines at 3K where as his car is a whole nother ball bark. I was under the impression that the 220A alt would produce more than factory at idle and cruise speed?

[ssh 924]

I was on the phone with mechman for about an hour during his order. we got the smallest pully that was safe for his car and the 220 should be the alt that is able to produce decent power at high and low RPM's. I have the alt that sacrifices power at low RPM and provides max power only when spooled to the upper ranges. his alt should produce considerably more power than mine does at idle. difference is I drive a diesel that red lines at 3K where as his car is a whole nother ball bark. I was under the impression that the 220A alt would produce more than factory at idle and cruise speed?

 

I don't know specifics about their products, so I can't really answer that question. This is the topic that reminded me of what it sounds like your friend is running into: http://www.soundsolutionsaudio.com/forum/topic/52554-sooo-i-got-a-gift-and-its-almost-here/?p=865825

[ncc74656 2]

reading it now, thanks

[ncc74656 2]

I just got off the phone with mechman, their alt turn on is 300rpm so I doubt that is not turning on at all but they did say the added stress to the engine may be causing below nominal engine RPM's and thus less power comes out at idle. seems to make a bit of sence I suppose but id like to know how to remedy that.

[ncc74656 2]

ok so he had orilies test it on their bench and they found that it was  putting out about 60A at max power. Im not sure how orilies testers are tho, never used them?

[pmureika 31]

I just got off the phone with mechman, their alt turn on is 300rpm so I doubt that is not turning on at all but they did say the added stress to the engine may be causing below nominal engine RPM's and thus less power comes out at idle. seems to make a bit of sence I suppose but id like to know how to remedy that.

Normal engine idle rpm's are 500 to 600 for a gas engine. At 300 it will probably shut off.

[pmureika 31]

 

I just got off the phone with mechman, their alt turn on is 300rpm so I doubt that is not turning on at all but they did say the added stress to the engine may be causing below nominal engine RPM's and thus less power comes out at idle. seems to make a bit of sence I suppose but id like to know how to remedy that.

Normal engine idle rpm's are 500 to 600 for a gas engine. At 300 it will probably shut off.

 

I can increase the load on my 2009 jeep and the idle stays the same. Just the voltage drops. I am running a 300 amp mechman.

[ssh 924]

ok so he had orilies test it on their bench and they found that it was  putting out about 60A at max power. Im not sure how orilies testers are tho, never used them?

 

I would run the test again at multiple RPMs and record the output, then you'll have a rough power curve.

 

Then you have three options (since you can't change the pulley size):

1) depending on the power curve you could raise the engine idle rpm enough to where it makes decent power (provided it's not idling excessively high)

2) add another battery so you have some extra reserve at idle, but it'll also be an additional current draw overall so it may not be optimal. Figure the stock electrical likely requires the majority of that 60A at idle if not more + the current draw from the amps (attempting to pull 2kw) is likely greater than what two batteries are going to provide.

3) get another alt that makes power at idle.

[Mattl 0]

I just installed a h/o alternator in my truck and am having the same kinda problems. If you find out what the problem is, I'm very curious to hear what it is.

[ncc74656 2]

i had issues with my batteries not charging fully in my truck when i had the 240A alt from mechman. my truck would not start many mornings due to this and my voltage would also often drop when driving down the road. the stereo had no bearing on or off to the batteries not fully charging.  i upgraded to the 380A and now  have no issues at idle like i once did and my batteries stay fully charged. i dont know why as i expected the idle performance to be worse but its much better with the larger alt.

[gsWes 4]

I had the same issue with my mechman.. Few things.. Make sure your belt is a quality belt and that it is tight enough.. If a smaller than stock pully is on the alt you will need a slightly smaller belt. Also my xs was crapping out at the time i got the mechman so i group 65 diehard platinum and a 1 inch smaller belt solved my problem.. I also took my truck to the dealership and had them turn the idle up from the factory setting of 625 rpm to 700. Now i have literally NO voltage drop at full tilt and every possible electrical component turned on! 14.2 ROCK SOLID! Fyi.. Napa sells rebranded " gates" belts for about 20 bucks