blase

I'm having an electrical problem, and although my battery and alternator are both fine, (replaced both of them) the car won't charge. I've tested the cable from the alt to the battery, as well as the 4 wires on the alternator harness, and they're all doing what they're supposed to do. I checked all my fuses and everything's good. Would a bad ground/short/open loop cause an alternator to not charge? Anyone know what to troubleshoot from here?

Thanks,
Blase

Kamin

you did a voltage drop test on the alternator cable? (measure voltage @ post on alternator, and at battery, subtract the numbers) it sounds like you have overlooked something.

blase

yeah, there was no difference in voltages between the alt post and the battery posts, or the 12v wire on the alt plug. Although there is a .5v difference between key "off" and "on".

blase

I should however mention that there was also a .5v difference between positive to negative battery terminals compared to positive terminal to ground.

JimBlake

Check the 'C' wire in the alternator harness. I think the ECU can 'shut off' the alternator by bringing that wire down to ground. But if that wire's rubbed thru somewhere & touching ground, then ???

Don't forget to check for open ground cables too.

blase

What kind of voltage should I be looking for from the C wire? (special instructions, ignition position, voltage difference, etc...?)

blase

What kind of voltage should I be looking for from the C wire? (special instructions, ignition position, voltage difference, etc...?)

blase

anyone?

TypeR0186

maybe you have something hooked up wrong that is draining the battery. like amp or soo...

JimBlake

(Been away for a couple days.) I haven't had to check this on mine, but here's what I've read...

The voltage regulator supplies about 8.5v thru the C wire, to the computer. If the computer wants to 'turn off' the alternator, it grounds the C wire - causing it to go to about zero.

If that wire is shorted to ground anywhere, then that'll shut off the alternator. Even though it's not the ECU giving the 'command'.

Did you also make sure ALL your grounds are OK? It sounds like you got 0.5v across your battery ground cable, right? How about the grounds from engine to body? That's just as important.

blase

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">
The voltage regulator supplies about 8.5v thru the C wire, to the computer. If the computer wants to 'turn off' the alternator, it grounds the C wire - causing it to go to about zero.
</TD></TR></TABLE>
I checked the resistance on the C wire and the 12v wire to the chassis ground to see if there was any continuity, and both had continuity to ground. (This was with key off.) Interestingly the power wire showed 12 ohms resistance while the C wire showed exactly double. No idea what that means.

Then I pulled the harness off my ECU and tried to test the other end of C wire to chassis, and I got no continuity at all. (Which is really weird, unless I wasn't making good contact or something.)

When I turned the key on, the c wire gives me about 7.2v whereas battery voltage is about 10.9.

I also tested the ELD under the fuse box, which should have given me battery voltage, but instead gave me 7.3v (power) and 4.5v (signal). And as soon as I turn on the headlights, signal voltage drops to 0.

The main relay also starts clicking like crazy when the battery gets weaker, but goes away on a charged battery. (battery is definitely good.)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">
Did you also make sure ALL your grounds are OK? It sounds like you got 0.5v across your battery ground cable, right? How about the grounds from engine to body? That's just as important.</TD></TR></TABLE>

I tested the 3 main grounds I know of (head, tranny, thermo). Are there other ones I should know about? Also, is the .5v normal? Does it mean something?

Thanks man,
Blase

JimBlake

Someone here once gave me a link to an article about Honda charging system wierdness. Basically, the fact the C wire exists at all is sorta unique. (I gotta try to find that.)

The C wire goes to the ECU, so when you first measured it, you were measuring thru the output transistor (or whatever) of the ECU. When you disconnected the ECU, now that wire has no continuity to ground (good). The testing I mentioned should be with the engine running.

Similar, when you measured resistance of the (+) wire to ground, you were measuring thru the rectifier, which might not mean anything for now.

I think the ELD gets a regulated reference voltage from the ECU, which is less than battery voltage. I figured it would be 5v, but ???

You're getting pretty specific by this point, so I gotta wonder about differences between models & years. I should have asked about that right away. A Helm repair manual for your car would be a really good thing for you to have.

blase

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">
The C wire goes to the ECU, so when you first measured it, you were measuring thru the output transistor (or whatever) of the ECU. When you disconnected the ECU, now that wire has no continuity to ground (good).
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God, that seems so painfully obvious. Not sure how I missed that the first time.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">
The testing I mentioned should be with the engine running.
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Not sure how to do that... Am I supposed to unplug the distributor harness with the engine running? Or just poke through the wire with the leads?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">
I think the ELD gets a regulated reference voltage from the ECU, which is less than battery voltage. I figured it would be 5v, but ???
</TD></TR></TABLE>

Sorry to comprimise clarity for brevity. The ELD has 3 wires, right? According to my manual, the outer one should be battery voltage, the middle one should be 5v and the last one should be ground. Did the values I got seem tolerable?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JimBlake &raquo;</TD></TR><TR><TD CLASS="quote">
You're getting pretty specific by this point, so I gotta wonder about differences between models & years. I should have asked about that right away. A Helm repair manual for your car would be a really good thing for you to have.</TD></TR></TABLE>
Sorry, I should have mentioned it earlier. Its a 95 Acura integra USDM. It's got a 98 JDM LS in it, but OBD1 USDM alternator, IM, ECU, injectors.

Honestly, I need an acura factory service manual, because my Helms manual just isn't cutting it anymore. It does a great job with general overviews, but never gets specific enough to be really helpful. I want multi-volume manuals damnit!

By the way, thank you so much for your help. I have to say, you're probably the most informed person I've ever talked to on this forum.

-Blase

JimBlake

For testing, I guess I'd back-probe the alternator C wire on the ECU plug (A16), because the plug on the alternator is probably all sealed up & waterproof. If that didn't work, maybe make up some kinda short jumper wires to put inbetween the alternator & it's plug. Sorta like a break-out box.

If you've already got a Helm book, that's the same as what I've got. I've been told that's the same as the factory, so ??? Maybe what you want is a Helm electrical troubleshooting manual. So far, my car hasn't screwed up bad enough to need one so I'm not completely sure what's in that book.

blase

So I screwed around with it for a few more hours, and finally gave in and had it towed to an electrical specialist. (It feels weird to not be doing the work myself.) I'll keep you posted on the outcome explanation.

In regards to the Helm manual (inch thick, bought it at autozone?), mine doesn't have many of the specifics we talked about (i.e. 8.5v from C wire). I thought they write those books based on a complete teardown of the car, with no direct affiliation. For example, my book told me to fasten the EM bolts with 57 ft/lbs of torque. After shearing 2 of them, I talked to my Acura Service buddy who told me some of the stuff in those books was flat out wrong. Anyway, just my 2 cents.

Again, thanks for the help, and I'll keep you posted when I get a verdict.

-Blase

EE_Chris

I have a fantastic article on Honda's Charging System - I had a link to it, but it seems its been taken down. I do however have it on my harddrive - so shoot me an e-mail addy and I can send you this info (and anyone else is welcome to it as well). Its probably the article that Jim is talking about.

Also, the ELD does receive battery voltage and ground. The ECU spits out a 5v 'signal' which the ELD pulls to ground when current draw goes up.

EE_Chris

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blase &raquo;</TD></TR><TR><TD CLASS="quote">In regards to the Helm manual (inch thick, bought it at autozone?), mine doesn't have many of the specifics we talked about (i.e. 8.5v from C wire). I thought they write those books based on a complete teardown of the car, with no direct affiliation. For example, my book told me to fasten the EM bolts with 57 ft/lbs of torque. After shearing 2 of them, I talked to my Acura Service buddy who told me some of the stuff in those books was flat out wrong. Anyway, just my 2 cents.</TD></TR></TABLE>

The real Helms manual is around 4" thick, well, maybe 3". You should really look into buying this particular manual and not rely on the Haynes/Chiltons info.

JimBlake

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EE_Chris &raquo;</TD></TR><TR><TD CLASS="quote">Its probably the article that Jim is talking about.</TD></TR></TABLE>I believe that's it.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blase &raquo;</TD></TR><TR><TD CLASS="quote">In regards to the Helm manual (inch thick, bought it at autozone?), mine doesn't have many of the specifics we talked about (i.e. 8.5v from C wire).</TD></TR></TABLE>I've never seen a Helm book at AutoZone, I bet you got Haynes. But I HAVE seen them at public libraries. Buy from http://www.helminc.com or maybe a few dealers stock it. It's got lots of gory details about testing, but articles like the one Chris gave me help understand how it's designed.

blase

Today's random life lesson #427. Don't confuse Haynes with Helm. You'll waste 3 years under a hood, not knowing a better information source existed.

Thanks for the clarification guys. Time to buy a Helm.

SupaFly

Has it been fixed yet???
If so what was the problem??

blase

I got the car back. There was an internal fray in one of the alternator lines. (I'm assuming it was the C wire, but the guy barely spoke english.) I guess I must have hit it when I swapped the third motor in.

Thanks for everyone's help on this one. Merry Christmas and such...

Lord Helmet

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blase &raquo;</TD></TR><TR><TD CLASS="quote">I got the car back. There was an internal fray in one of the alternator lines. (I'm assuming it was the C wire, but the guy barely spoke english.) I guess I must have hit it when I swapped the third motor in.

Thanks for everyone's help on this one. Merry Christmas and such...</TD></TR></TABLE>

lol it's always the small things you don't see. good thing you got the car running right

EE_Chris

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blase &raquo;</TD></TR><TR><TD CLASS="quote">I've tested the cable from the alt to the battery, as well as the 4 wires on the alternator harness, and they're all doing what they're supposed to do.</TD></TR></TABLE>

Uh huh.

Glad to see you got **** running though.