Crazy idle drop NEED help!!

[hove 15]

I noticed this when I did my first Install and I didn't think much of it at the time because I was assuming my Alternator had a major roll to play with this. I received and installed my 270 HO alternator from DC. I am still getting really bad voltage drop at idle. Well i am driving it's fine i stay at 14.4-14.6... Once i hit a red light it drops down 12.2-12.4ish. If the heat or AC is on at idle i wanna cry

The only thing i have running in my car at the moment is my sundown 100.4 and i have 2x XS d3100 installed. 1 in the hood and 1 in the back.

I did some research and I read on trailvoy.com that the car PC tells the alternator to shut off at idle....called a dealership and they said thats not true.

so any advice will help

Thanks an advance!

[hove 15]

bueller....bueller..... LOL

[Tirefryr 1,742]

Just the 4 channel is causing this problem? Are you sure the batteries and alternator are okay? It may be new, but sometimes parts fail even when new.

[hove 15]

even with the 4 channel unhooked i get this issue... Connected DMM to the batteries they read fine at idle. I had an optima redtop in the hood before the XS and it did this with that berrter also. I am 100% sure its not the batteries or the alt.

I am clueless. I am replacing all my wires this weekend. so hoping that helps or fixes it.

still looking for opinions tho

[bassahaulic 155]

Maybe a MLA would help?

Or an XS Power VCM?

[hove 15]

Maybe a MLA would help?

Or an XS Power VCM?

what as an mla? After i got my alt installed the shop hooked a machine up that read how meny amps my car was pulling. and it was pulling 113 amps with everything off at idle

[Tirefryr 1,742]

Try only one battery and see what happens, or just go back to stock on all aspects. Sometimes going back to stock is the only way to narrow down the issue. The idle issue could be numerous things and not even related to the alt and/or battery upgrades.

[Tirefryr 1,742]

Maybe a MLA would help?

Or an XS Power VCM?

what as an mla? After i got my alt installed the shop hooked a machine up that read how meny amps my car was pulling. and it was pulling 113 amps with everything off at idle

There is a serious issue here somewhere. Even with all the lights on, AC running and windows going up and down, you shouldn't be drawing anywhere near that. Is the vehicle starting okay? the only thing I can think of that would cause that large of a draw would be the starter which would lead me to believe the solenoid was sticking somewhat or arching, but you would hear it. Only other thing I can think of it the cooling fans are staying on along with whatever other draws. Could also be a short in one or both of the batteries.

[hove 15]

Maybe a MLA would help?

Or an XS Power VCM?

what as an mla? After i got my alt installed the shop hooked a machine up that read how meny amps my car was pulling. and it was pulling 113 amps with everything off at idle

There is a serious issue here somewhere. Even with all the lights on, AC running and windows going up and down, you shouldn't be drawing anywhere near that. Is the vehicle starting okay? the only thing I can think of that would cause that large of a draw would be the starter which would lead me to believe the solenoid was sticking somewhat or arching, but you would hear it. Only other thing I can think of it the cooling fans are staying on along with whatever other draws. Could also be a short in one or both of the batteries.

sigh i hate my luck lol.

Car starts just fine. no random noise or anything. what would be the best way for me to find out what's drawing power? is there a way to find that out? also i should say it happens sometimes at red lights or idle. i would say 95% of the time it happens

[Tirefryr 1,742]

Pretty much the only way is to start pulling fuses until the draw is removed, then you have it narrowed down to a certain circuit, then you have to go through that circuit and find the draw. Just curious, but has your truck had the TSB done on the rear tail lights?

[hove 15]

Pretty much the only way is to start pulling fuses until the draw is removed, then you have it narrowed down to a certain circuit, then you have to go through that circuit and find the draw. Just curious, but has your truck had the TSB done on the rear tail lights?

I doubt it. i just got the truck last year and i was unaware of an issue with the tail lights. can you tell me more about it. i am searching for what your talking about right now also

[Tirefryr 1,742]

Pretty much the only way is to start pulling fuses until the draw is removed, then you have it narrowed down to a certain circuit, then you have to go through that circuit and find the draw. Just curious, but has your truck had the TSB done on the rear tail lights?

I doubt it. i just got the truck last year and i was unaware of an issue with the tail lights. can you tell me more about it. i am searching for what your talking about right now also

There was a problem (defect) with the circuit board on the LED tail lights. GM sent out a TSB (technical service bulletin) but never a recall. IF you go into a dealership it was fixed for either free or a small fee. It applied to the Trail Blazer and Envoy up to 07 I believe.

[Duran 387]

That's what I'd think, when you have your brake lights on.

[slim2fattycake 85]

Just a suggestion, check for belt dust on your alt pulley. I had to really tighten mine down because I had problems when I first installed it as well. Have you talked to Rob or Kyle yet? They may be able to pinpoint it for ya.

[mrbojang 8]

Can you try putting it in park at a red light (taking your foot off the brake) and see if the voltage goes up?

[jcarter1885 995]

Pretty much the only way is to start pulling fuses until the draw is removed, then you have it narrowed down to a certain circuit, then you have to go through that circuit and find the draw. Just curious, but has your truck had the TSB done on the rear tail lights?

Thats exactly what I told him when we talked an hour ago, I did the same thing today to find a draw that i had. If I leave the windshield wiper fuse in on the fuse panel inside my car, my headunit stays on even with the keys out of the ignition. When I unplug the fuse the radio cuts off, somehow it is allowing my ignition to keep drawing power. My car has electrical problems so that is nothing new to me.

[millertime 12]

how fast is your idle set ? i know on some it will not put out a charge if the alt. is not spinning fast enough.. maybe it has the wrong size pulley on it so it does not spin fast enough at idle

Edited October 26, 2010 by millertime

[ShagggDiesel 25]

I had this problem a couple days ago, I checked under the hood to find that a hose (some sort of vacuume hose) had come loose from my engine and was just sucking air, causing my car to idle rough and drop down to the mid 12's voltage wise. I connected the hose back to the engine and haven't had a problem since.

[Tirefryr 1,742]

HE has a draw, plain and simple. A vacuum leak is not going to cause the vehicle to draw 100+amps at idle.

[ShagggDiesel 25]

HE has a draw, plain and simple. A vacuum leak is not going to cause the vehicle to draw 100+amps at idle.

How are you so sure it's a draw? I thought that's what mine was because it was acting the same way.. only at idle.. dropping down to 12 volts and all it was was a vacuum tube. Not saying that's what it is, but I am saying that just because voltage is dropping, doesn't mean something is drawing significant amounts of power out of nowhere. There could be an engine/alternator problem.

[Tirefryr 1,742]

Maybe a MLA would help? Or an XS Power VCM?

what as an mla? After i got my alt installed the shop hooked a machine up that read how meny amps my car was pulling. and it was pulling 113 amps with everything off at idle

HE has a draw, plain and simple. A vacuum leak is not going to cause the vehicle to draw 100+amps at idle.

How are you so sure it's a draw? I thought that's what mine was because it was acting the same way.. only at idle.. dropping down to 12 volts and all it was was a vacuum tube. Not saying that's what it is, but I am saying that just because voltage is dropping, doesn't mean something is drawing significant amounts of power out of nowhere. There could be an engine/alternator problem.

Right there in red.

[ShagggDiesel 25]

Maybe a MLA would help? Or an XS Power VCM?

what as an mla? After i got my alt installed the shop hooked a machine up that read how meny amps my car was pulling. and it was pulling 113 amps with everything off at idle

HE has a draw, plain and simple. A vacuum leak is not going to cause the vehicle to draw 100+amps at idle.

How are you so sure it's a draw? I thought that's what mine was because it was acting the same way.. only at idle.. dropping down to 12 volts and all it was was a vacuum tube. Not saying that's what it is, but I am saying that just because voltage is dropping, doesn't mean something is drawing significant amounts of power out of nowhere. There could be an engine/alternator problem.

Right there in red.

My Apologies. I over read that portion.

[Tirefryr 1,742]

It's all good; I'm just trying to help him from doing more than he has to. Electrical gremlins are already enough of a pain.

[stevemead08 752]

Is it the same problem with the A/C off? Fans draw quite a bit of power. if one or both has a motor going out it could really draw more.

[Julian 641]

I had a problem similar to this, did you replace all of your stock wiring that goes to your battery? if so something could be grounding, and did you disconnect your positive post (stock wiring) on your alt and just leave it there? if so that could be grounding.