Major Electrical Problem? - Honda Prelude Forum

ion_four · 09-15-2008, 05:37 AM

Hi all, I've done a bit of searching, can't really find an answer and am in a pickle, since I need to drive out of state in the next day or so! Can someone please help?!

I just bought a 99 Prelude, on Thursday night. (Did a carfax and had a dealer look it over, then) I drove it about 50 miles to my Dad's work and everything was awesome, but when I went to start it on Friday night, nothing! (It turns out this is because I was using a copied key WITHOUT the "T5" security chip...using an original key solved the starting problem, but I still have an interesting issue, as follows!)

To diagnose the problem, I applied 12v to the starter and it fired right up. The car drove like a dream. However, the speedo and cruise control didn't work, batt and brake lights were dim, and eventually when I got home the ABS light came on! The next time I started the car, it fired right up, but before it got out of the driveway, the engine started to miss because battery voltage was around 8.x v!

The symptoms are exactly like this: *Weird* problem - speedometer dead/acting odd and charging system not working (long)

The person in that thread had their ECU replaced, as well as the alternator...the ECU seems like it would have NOTHING to do with this, but am I wrong? The car I have has been converted back to an OBD1 P28 ecu, with a Hondata s200 box. (It runs exceedingly well, btw, and seems to have been in this configuration for a few years.)

Testing my alternator yields only 12v output at 2500rpm, at best. The electrical system starts there and then slowly drops in voltage as it idles. The lowest I've seen at the battery is 8.8v, before the car takes a dump. So, I believe I need a new alternator and probably battery, since it's been taking a beating.

My question is this (since it's the newest car I've owned, and I have no helms manual): Is there any ECM in control of the charging system, or is it just the alternator, battery and ignition switch? Could I have hurt something by driving the car, when the "T5" key security system thought it shouldn't be running?

My plan is to pull the alternator and bring it to a parts store, as well as the battery since it's still under warranty. However, is there something else that could be damaged? I think one or more of the engine grounds have been removed, so I will be throwing a few back on. I really want to make sure this will be a long-term fix, since I have to drive a LOOOONG way, soon! Any help is appreciated!

ndantzler · 09-15-2008, 07:27 AM

I had a similar problem, and I just replaced the alternator. It was interesting though, because I had taken it to Advance a few days before and the guy told me the alternator was fine. Not sure if he knew exactly what he was doing. I can tell you for sure that replacing my alternator fixed mine though.

ion_four · 09-15-2008, 12:24 PM

Yup, I just had Autozone test the alternator and they said it was fine. I got a new one, anyway. I don't see how it can be good when it's only putting out 12v at 2500rpm. This is also the opinion of a tech at the Honda dealership. I trust this over some ridiculously simplified test machine.

I also went to Wal-Mart (where the battery is from) and after charging it for an hour, they told me it was fine!

We'll see how it works out in a bit, when I fire it up again! I'm tempted to buy a new battery anyway, just to make sure everything is good.

ion_four · 09-16-2008, 06:33 AM

The starter has been replaced, and the belt is tight, but I'm still losing voltage while the car is running, because the alternator isn't charging!

Is it possible this has something to do with the Immobilizer? Or, does the ECU do something to control charging and the speedo/cruise? The car runs and drives great, but I doubt I could get more than 15-20 minutes of driving before the battery voltage was so low that the ignition would cut out. The speedo and cruise still don't work and the BATTERY light is on when the parking brake is off. Something is totally screwy.

I got the factory electrical manual section, and am digging, but have little idea what I'm looking for...

Sol Badguy · 09-16-2008, 12:00 PM

I would check all grounds and conections. Make sure thy are tight (9 foot pounds I believe) and free of dirt that can cause issues. Good luck. Maybe get a rental to go out of town, wouldn't want to get stranded

ndantzler · 09-16-2008, 03:18 PM

Sorry, but I think you need a new alternator

ion_four · 09-16-2008, 04:48 PM

Quote:

Originally Posted by ndantzler

Sorry, but I think you need a new alternator

I actually already replaced it. However, this seems to have been in vane! I downloaded a copy of the factory service manual and in following those diagnosis instructions, I found I had a bad ECM fuse! I checked this before and it looked good, but there you go! Replacing it has gotten me back up to 14v, at idle with no accessories running!

Helms manual FTW! So, this seems to be fixed!

ndantzler · 09-16-2008, 07:33 PM

well congrats, sorry if I cost you a new alternator or something crazy like that

ion_four · 09-16-2008, 09:51 PM

Nope, it was my own ignorance and inattention that cost me a new alternator! At least I found a pdf of the service manual, before having it towed to a repair shop!!!

Now that everything seems to be sorted away, I'm driving from Orlando, FL to Portland, OR!!!! I've done this once before, after purchasing a 93 Honda Civic only weeks before the trip, so hopefully my cross-country Honda fortune will continue!

FYI, the Helms manual (if you don't have it) has terrific trouble shooting flow charts. Without this, I'd probably still be up sh*t creek!

ndantzler · 09-17-2008, 07:16 AM

You driving through Colorado at any point?

ion_four · 09-17-2008, 08:44 PM

I'm not sure...We're in Chattanooga, TN, right now. We don't really have a particular route, but we do have to be back in Portland, by Sunday.

ndantzler · 09-18-2008, 07:18 AM

Chattanooga? Really? Say hi to my grandpa for me

And good luck with the trip. Those cross country trips are a bear

ion_four · 09-19-2008, 07:37 AM

Thanks! The trip was going well until yesterday. When I was getting gas I checked all the fluids and looked under the car. The right-side axle seal was leaking something fierce. I topped off the (manual) transmission in the parking lot and I only lost about .25 quarts, so probably no damage. So, the local Honda dealership is replacing it, this morning. It should be done in a few hours, so no biggie, unless they find out my axle carrier bearing is hosed. ha!