jdmark1

iTrader: (2)

In diagnosing an electrical issue in my Integra, I've gone down a rabbit hole of just learning about all of the different circuits in our cars and how they work. I got to reading about the ELD (electric load detector) and came across a few people linking to an old tech briefing. Unfortunately, the link was dead, but the original link was - https://www.smpcorp.com/download/view/tt1q98.pdf. I really wanted to read about it though, so I used the Wayback machine and actually found the old pdf. So anyway, I re-uploaded it. Here is a brief tech overview of the ELD system - https://drive.google.com/file/d/1LGe...ew?usp=sharing

DCFIVER

This is a more detailed,current explanation. The ELD system is still in use on current Hondas:

https://opensiuc.lib.siu.edu/cgi/vie...text=auto_pres

jdmark1

iTrader: (2)

Thanks for the link, I'll have to read through it when I get a moment. Is your link still relevant to 90s era Hondas or is it more for mid-2000s? Or is thee not that much of a difference between the two? I don't know how much the system has changed over time.

TheShodan

iTrader: (14)

Stickied!

DaX

iTrader: (1)

It's definitely relevant to 90's era Hondas. I found this white paper last year when dealing with a charging issue on my 90 Honda Civic and it helped me diagnose a bad alternator (well...voltage regulator).

spAdam

iTrader: (1)

I find the ELD really useful for monitoring system load in data. It's nothing but an ammeter that outputs 0-5V. I did a conversion a while back with a current loop. The formula I got out of it was Amps = (-18.1 * ELD volts) + 79.3:

bigjon1378

iTrader: (2)

not sure if this is really relevant to this topic BUT i was always curious about turning the ELD off when using its input to use a wideband with hondata. any one have any info on that? its how i have my car setup and was always uncertain about it because the ELD is obviously there for a good reason.

DaX

iTrader: (1)

By disabling the ELD, it just means your alternator will always be outputting the higher voltage, which is a higher mechanical load on the engine at idle. This will slightly lower your fuel efficiency.

spAdam

iTrader: (1)

Correct. It's fine to run without the ELD. I'm always surprised at how infrequently people seem to use the EGR lift sensor input for wideband input though. EGR operation isn't even an option for any of tuned ecu options, as far as I know, so it's always a free input.

stin1

iTrader: (1)

There is a lot of older threads against the eld for safety reasons. They said the eld shut off everything and created issues. The Canadian integras have no eld.

bigjon1378

iTrader: (2)

i didnt think most ecus have the hardware for it? only the vx ecu.

spAdam

iTrader: (1)

Exactly. But the 5V input still works. You’re supposed to add a capacitor though. It’s definitely available on P28s, but that’s all I’ve used since I started tuning these cars.

I’ve never had an issue with the ELD malfunctioning, personally, but I do shut off alternator control while tuning, especially for light throttle stuff.

DCFIVER

I wouldn't disable the ELD with out adding some other type of alternator control. The voltage regulator is computer controlled and disabling the ELD will cause the ALT to full charge at all times.

No alternator is designed to be at full output at all times.

You will shorten the life of the ALT and possibly cause other electrical damage.

spAdam

iTrader: (1)

The regulator is still functional and the alternator runs at a normal ~14V without the ecu alternator control. These are separate functions... the alternator control in these Honda ecus can put the alternator into a low power mode, just enough to keep the battery charged but not enough to charge it, in order to save a little bit of gas during times of low demand.

DCFIVER

Really?What is the current output with the ELD removed?

(Also current model Hondas regulator is completely computer controlled. I forget we are mostly discussing 25+ year old vehicles on this forum)

spAdam

iTrader: (1)

I'll grab a log sometime where you can see it doing its thing. It depends on a few different parameters (speed, aircon state, MAP, TPS) to decide. It's not terribly well documented but you can infer what is going on by looking at the data.

spAdam

iTrader: (1)

Here's a good example:



You can see in the middle graph what's going on. The white, red, and yellow lines represent battery voltage, alternator control, and system amps, respectively. When the correct conditions are met, the ecu signals the alternator to step the voltage down, but load (amperage) stays about the same. Voltage before the altc turns on is ~14, and ~12.5 after.

Power in electrical world equals current times potential (amps * volts). Think of this as the same as a fluid system where the amount of "stuff" going through equals volume times pressure. The ecu has no control over current, this is determined by how much the system (ecu, fuel pump, ignition,lights, etc.) are demanding. It does have control over how much voltage it can put out. So effectively, it lowers the system "pressure" in times of low demand to save some power draw, and hence, some fuel.

DaX

iTrader: (1)

^great explanation and graphical representation.

spAdam

iTrader: (1)

Thanks. I realize now that the lines are a little hard to see in a pic, it's a side effect of running a super high resolution on a 13" monitor so I can cram lots of stuff on it at once. Reading glasses are necessary when using my laptop, lol.

Freedo_Civegra

I wasn't looking for this just now, but I guess I'd be safe removing the eld from the 03 accord v6 electrical circuit after looking at this. I'll be able to run a more compact fuse and relay box where I've got my current one tucked.

BR1

I just went through several hours of diagnosing this system also. I bought a 2006 CRV, one owner with zero rust. the owners got dash lights so they took it to goodyear. they replaced the battery. then the next day put a new alternator on it. still had issues. Honda suggested that it needed a new PCM for $1200 due to the no charge/intermittent charge problem. They decided to sell the car. This forum was of great help to me. Sometimes it would charge at 14+ volts, but would not respond to high current draw forcing back to high charge. I tested the ELD, it was working fine. I have some pages of the FSM, and the SIU link which are awesome. checking voltages on the pcm connectors, everything was in order, except, when it should be in high current draw mode the Field Rotor was still at 5V - not good. Also, when ignition on run, the battery light did not come on. So now i'm thinking that there is an issue with the alternator. tear the front radiator support out enough to get to the alt 4 pin connector and check for power at the IG wire, 2 volts - bingo...12V is not getting to the voltage regulator, so it can do nothing. the VR is basically the brains of the alternator. i check continuity at a few spots and finally find the broken IG wire, and the broken L wire. now its all working again.

mikemurphy

I've recently had some issues with fluctuating voltage that may be related to a bad ELD. The alternator, battery and ground connections all checked out fine. Do you Know if these ELDs are the same in all honda or are they different depending on the vehicle and year.

jubjubub7

Thanks for posting - super informative and something I’ve been needing to learn more about. I had low voltage in my 97 Civic coupe (swapped with a 97 jdm itr running s300 v3) about a year ago and put in a new Bosch alternator. This seemed to fix the issue for the most part, other than now getting a “ghost” check engine light. Light is on but no codes present… Perhaps ELD or something to do with me switching to LED bulbs in the instrument cluster? I have a suspicion it’s something to do with the wiring/power but don’t know where to look next. I have noticed a slow drain on the battery which almost seems like something is grounding out somewhere… I’ve dug through the engine harness and not found anything to date. Boy, gotta love old wiring! I’d love to hear if anyone has run into something similar. Next I’m considering installing a solid state relay for powering my gauges and JDI GhostLock…I’m not a fan of blind trial and error but my thought is that cleaning up wiring under the dash may reveal something.

Rick O'Sidhe

Currently working the same issue with an '05 CR-V. New battery, alternator, ELD in chasing the problem. Scantool shows PCM constantly commanding 14.7V with IG1 High (ALTC). ALT-FR showing constant 97% output with moderate to high loads and cycling between 70-97% on low/no load. ELD indicates amperage appropriate to load. Then, randomly, ALT-FR goes to 0%. Can sometimes get it to kick in again by modulating the load and revving to 4-5K. When it's working, it seems to be stable at idle with no load (no dropouts). Can turn engine off, switch to Run and the dash battery light illuminates. When ALT-FR is on the fritz, then only get a momentary 'flash' illumination of the battery light at Run/Start.

Troubleshooting this has been incredibly frustrating, and the next obvious step is to go through what you did & hope like hell that I can get enough room up top to backprobe the ALT connector. I'm suspecting that the new AC Delco alternator has a fried regulator because it was working for a couple of weeks after install, but with my luck, it's going to be a broken/frayed ALTC wire shorted to ground or an open in the 12V ignition wire in the battery harness. Really not looking forward to R&R of the harness, much less ripping it open and inspecting every inch.