Alternator Issues after installing hondata

[Cdoome2]

I recently installed hondata 3b. It runs decent except for one issue, the alternator does not put out 14 v all of the time. I have my turbo timer set to Voltage Mode so it displays the voltage it reads. Now if i start my car, and let it idle, it will usually stay at around 14.0 v on the display. If i drive around, chances are, when i come to a stop, the voltage will drop to about 12.0 v. Now if I turn on the a/c the voltage will jump back up to 14 v, or if i rev the car past 3000 rpms it will also jump up to 14 v. Also when driving, if i reach 3000 rpm in a gear, or stay above 40 mph, the display will read 14.0 v. I went to autozone and they did the little free test. He told me the alternator was fine. so this leads me to believe something is wrong with the ecu, or the wiring from the obd2-obd1 conversion. Any insight would be appreciated.

[AndyE]

What you describe sounds like normal alternator behavior. Did your alternator behave differently before you installed the ECU?

The voltage regulator circuitry that causes the alternator field current to kick on and off (and thus control the output voltage) is located on the alternator itself on most Hondas, and is thus independent of the ECU. So changing the ECU shouldn't affect your charging system.

There's a good overview of how starting/charging systems work on this page.

-AndyE

[Cdoome2]

My car NEVER acted like this, its so bad, the lights dim bad. its pathetic, its actually embarrassing, Im having to buy another darn ecu, cuz no one knows whats going on.

[Hondata]

Tell us more: Are you using an adapter harness? Have you tried another adapter harness? What sort of ECU is it? Have you tried another ECU as the ECU could be faulty? Who did the install and what sort of ROM did they use?

[Cdoome2]

Yes, I am using an adapter harness, I have yet to try a different harness, but I just bought another ECU that should be here soon, the ecu in my car now is a P06 I believe ( i have a 98 integra ls). Secret Services did the install, Great guys, great service, but we just couldnt figure out why when im below 3000 rpms most of the time my alternator stays off, unless i turn on the a/c or turn on my brights. then most of the time the alternator will kick on. I bought my hondata, ecu, and harness used, from a guy, maybe i should have bought it brand new, the harness looks a little ugly, but the connections are solid. My bet it is the ecu. we'll find out soon enough. Oh by the way he used EPROM. thanks for you help.

[LiLOtaku]

I'm pretty much having the same "light dimming" problem. I posted something about this in the "applications" forum. I am using a JDM PR3 ECU which wasn't on the list of ECU's to modify, but its still seems to be working ok. I'm also using a obd2-obd1 wiring harness for my 99 Si. My stock ECU doesn't ever do this. I'm using the EEPROM that came with the hondata kit, and I had a friend that works for the City do all my soldering for me and I know that his work is top notch.

[Cdoome2]

Yeah, I still havent been able to fix my problem. Looks like I'll be forking out the $$$ to switch standalones.

[JT]

Okay, I seem to be having the same problem since the Hondata 4B was installed. It didn't bother me at first but now it's driving me crazy mainly because I can see the lights dim when I drive in the dark. Here are some of my observations and things that I have tried.

Observations:
1. When the engine is started, the alternator would output the normal 14.5v to the battery.
2. During normal driving the voltage sometimes drops to 12.5-12.6 regardless of engine rpm, and would cause the lights to dim.
2. Increasing engine rpm would not help to increase the voltage, as it doesn't seem to be a alternator speed related issue. nor the belt is loose.
3. The voltage would sometimes come back normal at 14.5v after awhile during driving.
4. The voltage would ALWAYS come back if I reduce load to the engine slightly by letting my foot off the gas, as little as only .5 inch of vacuum change. However, increasing the engine load by slightly (.5 inch of vacuum change) would cause the voltage to drop again.
5. The voltage doesn't always increase if an electrical load is turned on such as headlights and AC.
6. The voltage would ALWAYS come back if I turn on an electrical load and turn it off again such as AC.
7. When the voltage is low, the rpm also falls.
8. When the voltage is low during idle, turning the engine off and start it again would ALWAYS bring the voltage back to normal.
9. The problem seems to be from the ELD circuit not able to detect the engine load correctly.
10. My wife has the exact year/model Civic and her car doesn't have this problem.
11. The car doesn't have any other problems at all except for the low idle at 600-650 rpm issue... Perhaps the low voltage is causing the low idle.
12. The entire Hondata package which includes the 4B, adapter harness and P28 ECU was shipped directly from Hon
data.

Things that I have tried:
1. I replaced the alternator with the same result.
2. I replaced another P28 ECU with the same result.
3. Checked belt tension.
4. Checked battery conditon. Green eye is still on and it holds charge.

I was wondering if the S200 upgrade would fix this problem, as I notice Rom v3 has a feature to disable the ELD sensor. Please let me know if there are anything I should try.

Thanks,

[Hondata]

The ECU looks at the rpm, load and ELD and will reduce the alternator output in order to save fuel at cruise. It seems that it is doing this when it should not. It could be from a vehicle difference between the OBDII vehicle and OBDI ECU, or it could be a wiring issue, or it could be that parameters are slightly different OBDI to OBDII causing the ECU to mis-read electrical load. If you're going to substitute anything for testing, try the ELD and voltage regulator.

First:

1. Check the ELD voltage reading in the ECU between pins D10 and B2. Turn the lights on - this voltage should drop. It might be a good idea to check the ELD voltage in the stock computer (sorry, don't know the pins) to check that you get the same reading stock vs OBDI.
2. Check the ALTF wire runs correctly from the ECU D9 pin to the alternator plug.
3. Check the ALTC wire runs correctly from the ECU A16 pin to the alternator plug.

Second:

Unplug the ELD connector from the engine fuse box. It is the small 3 pin connector underneath the fuse box (you'll have to lift up the fuse box and remove the bottom plastic cover). If it is easier remove pin D10 from the ECU connector. This will give you a ELD error but will tell you if the problem is caused by the ECU misreading the ELD and reducing the alternator output when it should not.

I'll investigate the ALTC operation and see if there's anything in the ECU that might cause the problem.

[Cdoome2]

I fixed my alternator problem, heh by disconnecting the alt c wire, the problem went away for good, but there is still no explanation, doug didnt know the cause either, but anyways, the problems gone.......now only if the partial throttle hesitations were gone, id be in heaven!

[JT]

Okay, I have tried everything that were suggested except checking the ELD with the stock ECU because I need to find a set of 240cc injectors... Then again, the car didn't have the voltage problem until converted to OBDI...

Here are the results.

ELD voltage when voltage is normal:
Idle = 3.52v
Parking lights on = 3.25v
Headlights on = 2.75v
Highbeams on = 2.71v
Brake lights on = 3.52 (no change)

ELD voltage when voltage is low:
Idle = 3.55v
Parking lights on = 3.31v
Headlights on = 2.85v
Highbeams on = 2.82v
Brake lights on = 3.55v

1. ATLF and ATLC wiring continuity checked out okay.
2. Disconnecting the ELD connector caused the voltage to remain normal under all conditions.
2. The idle speed has increased to 850rpm with the ELD disconnected.
3. Hondalogger registered an ELD error. However, the CEL on the dash never came on.
4. Replaced the ELD with another unit but it has the exact voltage problem, so the ELD is not the cause.
5. Disconnected the 4-wire interface cable from the Hondata unit with the same result, so the problem is not the Hondata unit either.
6. Swapped out the P28 with another unit didn't fix the problem, so it's not the ECU.
7. The alternator has already been replaced (the voltage regulator is build-in) but it didn't fix the problem.

The only thing left that I can think of is the OBDII to OBDI harness and possibly a compatibility issue with the P28 ECU. Any updates on the P28 ATLC circuitry operation? Anything else to try?

I'm a little tire now... but not ready to give up yet!

[Sevedd]

I noticed that someone has posted to remove the Alt-C wire. Hondata(Representative) have you come across any other updates?

Thanks

[Carchitect]

Try rewriting the chip with the same program with the ELD disabled. This fixed the problem I was having with the OBD-1 ecu swaps in the OBD-2 civics.

Joe.

[Jaker]

As a manufacturer of OBD conversion harnesses, I can say that we also have had issues with the ALT C connection. Seems that some of our customers have had difficulties with this connections limiting the output of the alternator.

I personally run our product, but have never had any issues with this. We will be updating our product to eliminate the ALT C connection.

[sr20det]

that shit is normal 4 a alt going bad it happened in my mustang an i just put a bigger alt do u have a "system" if not mayber somthing else is draining power