Dropping Alternator Charge Voltage - ELD Enable/Disable

K-Series Programmable ECU installation questions / support issues
MacLotus
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Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by MacLotus » Fri Apr 11, 2014 8:27 am

I have a K24A2 w/K20 wiring harness and K-Pro ECU installed in my Lotus Elise. As such, the Lotus has no ELD. Also note I have no stereo system, AC, or other power hog devices.

Issue: When the car starts cold, the charge voltage from the alternator (measured at the battery terminals) is 14+vdc. After running a minute or two, the idle changes slightly and the voltage drops to 11.8vdc and starts dropping.

Thinking I had a bad alternator, I purchased a new one. The problem continued. I took the alternator out to be checked and it checks good. The battery is also new. I began to research on the alternator and found several posts regarding 'bypassing the ELD' on forums where guys are running BIG sound systems.

I was advised to unselect the 'ELD ENABLE' in the Misc Tab of K-Manager, but that seems to have little effect on turning the alternator back on. I read in previous posts on this forum that the ELD Enable only disables error reporting and will not have any affect on the alternator charge mode. Can you please confirm.

About the ELD Bypass: It's my understanding that inserting an 820 ohm / 1/2 watt resistor from Pin 15 / E Connector to ground will make the ECU see a load high enough to turn on high charge mode.

Another option is to try installing an Honda ELD. Any advice or insight to my problem?
Ken

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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by Spunkster » Fri Apr 11, 2014 2:36 pm

Have you tried following the Charging system troubleshooting steps in the RSX Helms manual (factory service manual)?

MacLotus
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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by MacLotus » Wed Apr 16, 2014 12:41 pm

Thanks Spunkster. I have used the manual for troubleshooting, but then I have an aftermarket modified ECU. So my question is directed at Hondata regarding the ACTUAL functionality of the ELD toggle in K-Manager.

"I read in previous posts on this forum that the ELD Enable only disables error reporting and will not have any affect on the alternator charge mode. Can you please confirm."

Thanks,

Ken
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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by Hondata » Wed Apr 16, 2014 2:27 pm

The ELD input only provides an idle up for the engine. It doesn't change the alternator control / output.
Hondata

MacLotus
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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by MacLotus » Sun Apr 20, 2014 12:53 pm

Hondata wrote:The ELD input only provides an idle up for the engine. It doesn't change the alternator control / output.
Thank you for your response. Actually, the FR circuit between the Alt and ECM B Connector Pin 13 is responsible for controlling engine idle. Not the ELD sensor. I put some additional information below explaining how the Honda Dual Charging System operates (just as an FYI).

That aside, I have found some discrepancies in the Hondata wiring diagram. I point these out not to be a 'detail freak', but because it's creating some issues during the troubleshooting process as outlined in the Honda manual (2004 Acura RSX Type S).

Image

The issue I'm having begins with the first step in the Honda troubleshooting procedure outlined in the manual... Charge Indicator Lamp Test. My issue is there is no output (or pin for that matter) on C101 pin 8. The wiring to the lamp (which I installed per this diagram) is installed, but the Honda ECU does not provide any trigger there for AltL (Blue/White wire). I did apply a ground to pin 8, and the lamp on my dash lights just fine, so my wiring is correct... but the wiring diagram is incorrect.

Here are the Honda PRB ECM pinouts out of the manual.

Image

They didn't label the connector above very well, so here's another reference to it with better descriptions.

Image

Image

Connectors C & D below are not used (A/T only)

Image

So there is a discrepancy in the wiring diagram for proper operation of a charge indicator lamp. I'd like to fix that, but I'm pretty sure it's not the root cause of my charging problem. To that, here is the Honda Dual Charging System diagram from the manual. I've correlated the Alternator pinouts to the ECM connectors for reference.

Image

Terminals & Modes

The voltage regulator utilizes five terminals: Ignition (IG), Control (C), Field Reference (FR), Battery, (B) and Lamp (L). The B terminal is the high current circuit that's responsible for charging the battery. The other circuits are located in a single connector and are responsible for controlling the voltage regulator located within the alternator.

The IG circuit is crucial to proper charging system operation. Turning the ignition switch to the Run position will send source voltage to the IG terminal, which is required to energize the voltage regulator.

The C circuit is responsible for controlling the charge mode (based on the voltage on the ELD circuit). So indirectly, the ELD controls the charge rate (High/Low). The voltage regulator sends a voltage to the ECM through the C circuit. Depending on the charging systems needs, the ECM either holds the voltage high to signal the high output mode, or it pulls the voltage low to signal the low output mode. When the circuit C voltage is pulled low by the ECM: the charging voltage at the battery will range from 12.4 - 12.9V. The ECM uses the low output mode when the engine is starting or if all of the following parameters are met:

electrical Load below 15 Amps (varies with vehicle)
vehicle speed between 10-45 mph or at idle while in drive
engine speed below 3,000 rpm
coolant temperature above 167°F (75°C)
A/C Switch Off
intake air temperature above 68°F (20°C)

Outside of these parameters, the ECM will hold the voltage on the C circuit, which will place the charging system in the high output mode. In this mode, the charging voltage at the battery will range from 14.4-14.9V.

Note: The ELD circuit is pretty easy to fool. Pull the ELD out and use a 600-800 ohm resistor to ground and the ECM thinks the car's current load is high (forcing C to keep the alternator in high mode).

The ECM uses the FR circuit for field rotor status to be able to change engine idle speed. If the alternator is under high load, the ECM will increase idle speed. While the engine is running, the ECM sends 5V to the voltage regulator through the FR circuit. When the field rotor is on, the voltage regulator will pull the voltage down and when the field rotor is off it will hold the voltage high to around 6vdc.

The charging system utilizes the L circuit to inform the driver of any charging system faults. Over the years Honda has used two methods for illuminating the charge warning indicator lamp. On older models, the L circuit directly provided ground for the warning lamp if a problem was present. If everything was in spec, the voltage regulator removed the ground by providing positive source voltage on the L circuit.

However, on late model vehicles, the ECM sends source voltage to the L circuit. If a problem occurs, the voltage regulator will pull the voltage on the L circuit to ground. If this occurs, the ECM will sense that the signal voltage has been pulled down and it will then send a “charge warning lamp on” signal through the CAN bus network to the gauge control module. In this case, the gauge control module will directly switch the indicator lamp on.


So the first question is, since the AltL signal (Ground) is not on C101 pin 8, where shall I connect the charge lamp to?

The second (or original question was), what exactly does the ELD enable/disable in K Manager actually do? I think the answer is 'It ONLY quashes ELD related codes.' and has nothing to do with what charge mode the 'C' circuit will output on the ECM Connector B pin 18.

Sorry for the long response, but I would like to address the charge lamp issue. I'm hesitant to T-tap the Blue/White AltL wire off the ECM Connector B pin 10 to the lamp until I hear back from Hondata. I don't want to cause any damage to the ECM. Maybe disconnecting it from the ECU and connecting it to the lamp circuit?
Ken

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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by Hondata » Sun Apr 20, 2014 6:25 pm

I don't think that information is correct, despite mostly being copied from Honda, but don't have time to analyze every part of it. In brief:
- ALTL was at position 8 on the harness I have. What the factory diagram shows is different, but the wire is there. If your harness is different, trace the wire from the alternator. It may be B10 for your harness.
- The ALTL is from the alternator to the charge light via the ECU. The ECU does not control it.
- The ALTC is not not used on the RSX ECU. ie it does not run in low voltage mode ever.
I'd disconnect ALTC and see if anything changes.
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MacLotus
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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by MacLotus » Mon Apr 21, 2014 6:18 am

Thanks for your response. Much appreciated. The information is correct for the K series. That said, you might have an old-type harness where the AltL output directly tied to the negative side of the charge light (old school... which I prefer by the way). You are correct. The ECU does not control ALTL (from the ALT), but rather uses the data for logging/cel, and passes it on to the light.

In the early 2000's, the charge light fell under the control of a smart dash (so to speak), receiving all sensor ECM data through a CAN bus (digitally). No longer was each light individually lit through simple circuits.

K20A2's were in the 2002-2004 Acura RSX Type S, which utilizes the CAN bus. That's why there is no ALTL on pin 8. But as I said previously, I know this is not the cause of my charging issue. I will try re-routing the ALTL to the light which I'm sure will resolve the problem with the charge lamp. Hondata may want to put a note on the drawing to address CAN bus applications.

I have disconnected the ALTC wire with no effect.

--------------------------------------------------------------------

With all do respect, I will take issue with your statement "The ALTC is not not used on the RSX ECU. ie it does not run in low voltage mode ever.". I don't say this to be disrespectful, but where did source this information? Maybe I'm misunderstanding what you mean, but that could not be more wrong? ALL Hondas use a dual-charge mode system and the RSX (all types) are not excluded.

I know email and text statements can inflect tone, so again I say with the utmost respect, that is a little unsettling to me personally. When I speak with Hondata regarding the functionality of a $1300 Honda ECM I purchased from them, I want to know their technical staff fully understand the details of its operation to a degree more than I understand it. This, IMHO reflects poorly on the credibility of Hondata.

If I'm wrong, my sincerest apologies. Please educate me by pointing me to data that supports that statement.

Once again, I'm grateful for your assistance with my technical issue. Thank you.

Ken
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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by Hondata » Tue Apr 22, 2014 7:50 am

MacLotus wrote:With all do respect, I will take issue with your statement "The ALTC is not not used on the RSX ECU. ie it does not run in low voltage mode ever.". I don't say this to be disrespectful, but where did source this information?
Low voltage operation is not enabled in the RSX ECU - this is based on looking at the ECU code. Apologies if this is in conflicts with your statement, but the ECU does not run in low voltage mode so what else can I say?
MacLotus wrote:ALL Hondas use a dual-charge mode system
Again, no they don't. The early OBDI vehicles did (like the Civic VX), the 2002-2011 generation did not (at least not the Civic, RSX or S2000), and the some 2012+ vehicles use low voltage mode (2012+ Civic for example).

Getting back to the original problem, what you need to do is measure voltage drop from the battery negative to the alternator body (and also to the G101 point on the manifold/cylinder head). Also I would measure the voltage drop from the battery + to the alternator ignition power (blk/yel). Observe both voltage values when the output drops - both should be very low (under 0.01V on the ground, under 0.1V on the power side).
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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by b16itb » Wed Apr 23, 2014 10:55 am

I used to have similar problem. Voltage sometimes was variating from 14 to 12v. All the lights and the fuel pump were wierd.

I just cut the ALT-C (B18). Problem solved.

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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by shanebadoo » Tue Apr 14, 2015 8:07 pm

Any update to this? I also have a dropping charge voltage from 6000-redline on a k20a2 swapped eg civic. Idle is fine and low rpm driving is stable and high (13.9), but under heavy accel, voltage drops tp 12.9-13.1. Any help would be appreciated

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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by Spunkster » Wed Apr 15, 2015 11:38 am

Who made the engine/charge harness?

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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by shanebadoo » Fri Apr 17, 2015 2:51 pm

Charge harness was self made. Oem gauge. Any recommendations? I have seen same issue in about 3 k swapped civics/integra.

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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by Spunkster » Fri Apr 17, 2015 2:53 pm

Try the ECU in a non-swapped chassis and see if the voltage drops. If it does not then you need to look at the wiring in these swapped vehicles as that sounds like the thing they all have in common.

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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by playasyougo » Tue May 19, 2015 3:19 pm

Hi,

I'm having the same issue with my K-swapped JDM Civic EG. The drop in voltage at high rpm is not allowing a full throttle shift system to work or a gear display.

My Civic uses Motec M130 ECU and Motec C125 display so it's not anything Hondata related.

I will try and disconnect the ALTC (B18) wire and test it out.

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Re: Dropping Alternator Charge Voltage - ELD Enable/Disable

Post by playasyougo » Wed May 20, 2015 1:28 pm

Checked my Rywire loom and no B18 pin or wiring going to the B plug.

No clue where to look now!

Any ideas??

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