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Original computer, eng, harness, except big3 upgrade using 4gauge and stereo install straight off the battery; not thru ELD. Was getting slow at starting so looked for parasitic drain. No drain w stereo system disconnected only~30mA connected. Head unit displays voltage and showed erratic charging ~9-~12v only holding solid 13+v with headlights on, no other load or combination making any difference. Pulled up the eng compartment fuse box & disconnected the ELD and put the fuse box back in. Now driving around a bit it's keeping 13+v w no DTC/ light but I'd rather have it all function correctly.
I'm thinking it's either voltage reg or computer faulty cuz bad ELD would give light/DTC...aaand....is having the stereo load not thru ELD somehow causing any of this? Like the computer not getting the whole load picture don't compute?
Joined: Mar 2010
Posts: 14
Likes: 0
From: Houston, Texas
Default Re: ELD (Eletrontic Load Detector) discussion | 96-00 chassisHello everyone at Honda-Tech. This is my first post but I've follwed the forum for a little while now. I've seen this problem (dimming lights, low charging voltage with light electrical loads) with a couple cars and even experienced it first hand in my 1997 civic ex 2dr with 2000 B16A. I have three stock ecus kicking around, all P72, one is obd1 the other two are obd2a. All three work fine, but only one of the obd2a ecus doesn't have this problem. The other two have the problem. As far as I can tell (through research of service information), the ELD (electrical load detector) monitors the electrical load on the system and sends a 1.5V-3.5V signal to the ecu based on that electrical load. Voltage could be higher or lower, but I think >4.5V or <.5 will set code 1298 (20) ELD circuit high input or 1297 (20) ELD circuit low input and illuminate the MIL. Higher ELD voltage signal means there is little to no electrical load, lower ELD voltage signal means there is a greater electrical load. If measured, the ELD voltage should drop a little each time a load is added one by one (indicators, brake lights, low beams, etc.). The ecu recieves this signal and uses it as a reference to control the alternator via the ALTC (alternator control) circuit. The ecu sends a battery voltage signal to the voltage regulator which essentially holds the alternator back, lowering its output and reducing load on the engine. At a certain point (not sure exactly what ELD signal voltage) the ecu responds and stops sending the battery voltage signal to the voltage regulator and the alternator output returns to normal. ALTC appears to be simply an off/on (0V/BATV) signal and should switch from battery voltage to no voltage with any electrical load, despite the size. I think the problem is the ecu not switching the ALTC to 0V when it's supposed to, but why? It seems that some ecus switch the ALTC to 0V as soon as the ELD signal voltage drops a little, while others wait for a more substaintial drop. I know that de-pinning or cutting the ALTC wire from the ecu connector solves the problem by stopping the signal from reaching its destination making 0V at all times. This is a quick fix but I think there may be a better way. Does the ecu ever send the battery voltage ALTC signal with loads? Perhaps when the engine rpm is higher and the alternator can meet the demand even when being held back by the ecu. I guess I'll check some stuff out when I have some free time and get some concrete information on the exact cause for this problem. Since I have two obd2a P72 ecus (one with the problem, one without) and all the necessary tools it shouldn't take more than an hour. Will post results as soon as I got them. Also, for the guys running the Hondata s300, what happens when you disable the ELD? Does it set a code 1297 (20) ELD circuit low input or 1298 (20) ELD circuit high input? What does it do to ALTC? Thanks people, and sorry for the length of this, it's my first time.
Joined: Jul 2004
Posts: 5,977
Likes: 479
Default Re: Help!!! car wont charge properlyThis is how the stock set-up is:
1. Honda's utilizes a dual mode charging system. The ECM/PCM determines charging based on info. from the ELD. During heavy load, the ECM/PCM can set charging voltage for high output (~14V - 15V). During light load and start-up, the ECM/PCM sets charging voltage for low output (~12 - 13V).
2. On the Civic, the 4 terminal wires at the harness connector are the following:
• Blk/Yel wire (IG): Ignition wire - Under-dash Fuse No. 15 (7.5A) and the IG wire supplies the ignition input that turns on the alternator/regulator assembly.
• Wht/Grn wire (C): Control wire
• Wht/Red wire (FR): Field Reference wire
• Wht/Blu wire (L): Lamp wire – wire the regulator uses to ground the charging system warning lamp in the gauge assembly.
The wires between the alternator's voltage regulator and PCM/ECM are the C and FR. The ECM/PCM can control charge modes (high or low output).
If under-dash Fuse No. 15 (7.5a) was blown or there was an issue with IG wire (Blk/Yel wire), then the alternator won't charge.
3. The separate Wht/Red or Wht cable that connects between the alternator and under-hood fuse/relay box is the Battery (B) cable. It is the alternator output wire that supplies current to maintain the battery and run the car.
Sorry if i posted this wrong but didn't see how else to do it.
Thanks Mucho!!!
Disconnecting the ELD at the bottom of the fuse box. Remove the bottom cover It's the 3-wire connector
I had to drive it around quite a bit. Coming to a stop the idle kept dropping too low and stall out. After a while keeping it from dying the computer (I think) got the idea that this is the new normal and it's not stalling now but still drops to around 400 rpm before getting back to normal idle.
Charging still 13v+ except at that moment of confusion about idle speed.
I'd still appreciate any input about this. Is it the computer?...since the V reg is doing it's job...?
charging problem 96hatch mostly stock
