*Weird* problem - speedometer dead/acting odd and charging system not working (long)
OK. Here's what happened... I was visiting my parents on Monday and Tuesday. Tuesday evening I left for the 70 mile drive back to my house. I get in my car and start it up to let it warm up while I load my stuff in it. I get in the car and start driving. I get about 100ft and, out of nowhere, my speedometer drops to zero while I'm moving at about 20-30mph. Also my parking brake indicator light and my battery indicator light both come on really dim. They are both on simultaneously but only maybe 1/3 as bright as they would be if they were actually on... I turned around and went back to my parents' house. I shut the car off, and then I restarted it. The speedo was still dead. Then I resest the ECU and restarted the car. I let it warm up and idle for about 8 min. I try to drive again, but The speedo was still dead...
At this point, I just decided to go and risk it because I had to get home... The speedo was still not working and the battery and parking brake lights were still on very dimmly. The car seemed to drive fine. And the tach was still working fine. It seemed to have full engine power, although VTEC would not engage because the speedo was out. It did idle really low though at 250-300 rpm... Here's the really weird part: If I let the revs get up to the VTEC range, VTEC did not engage. BUT the speedometer would spring to life at 5200rpm and give what looked like an accurate speed reading only above 5200! As soon as I dropped below this, it went right back to 0 mph...
I got about 65 miles before my problems got worse... It was getting dark so I had my lights on and I was listening to my radio. As I was getting close to home, all of a sudden, my ABS light comes on at full brightness. About 30 seconds later my stereo shuts itself off and simultaneously, my whole gauge cluster goes black and all the gauge needles go limp. All the gauges and indicator lights are now dead. Now at this point, I'm driving through a town with streetlamps. As I leave the town and the street lights, I realize that my headlights are *really* dim and barely even lighting the road anymore... It seemed like my battery was not charging for some reason.
I decided that I was not going to let my car stall out and get stranded. I was able to keep it just barely running long enough to get home. I pulled into my parking spot and let the car idle. It idled for about 20 seconds, then it died... It was too dark to see under the hood and it was late, so I just decided to get up early this morning to look at it... I look at it this morning before work. I could see no obvious visible problems... I tried to start it. Thinking that my battery should be dead by now, I did not expect it to start. To my surprise, it cranked a little longer than usual but then fired right up. I let it idle for about 2 min and it seemed OK. So I decided to try to make it the 10 mi to work. My speedometer was still dead, but the tachometer and other gauges were mysteriously back. Feeling brave, I turned on the radio. I drove all the way to work. About 2 mi before I got there, the radio died again, and my whole gauge cluster went out. I basically coasted into the parking lot and my car died again as soon as I stopped in a parking spot...
So now I'm at work and I call the dealer to see if they can look at it today... They say "bring it right over" and I say "I'll try". So I try to start it again. the car cranks for about 5 sec, but then starts right up. I drive about 16 mi to the dealer. I had no radio or any other power accessories running this time. The speedo is still not working, but the other gauges are now working again. This time, the whole gauge cluster dies on the highway about 3/4 of the way there. Again, I just barely make it to my destination. The car stalls as I enter the dealer lot. I tell the dealer this whole story, and I leave my car there.
The dealer calls me about 3hrs later. They say my alternator is bad, and I need a new one. They have no Prelude alternators in stock so they have one overnighted from Ohio. I asked them about how my dead speedometer factored into this and how they were fixing that. They told me that the low current affected the speedo gauge... (This seemed very odd to me... Why would my speedo go before say any other gauge or before my radio or before my lights or whatever? How much current can a freakin' speedometer draw?...)
It can't be JUST the alternator - Can it? Any other thoughts or ideas? Anybody ever hear of anything so weird? I guess I'll find out tomorrow when they get the new alternator on...
Oh, also, they scolded me about my Mugen header. They said that the excess heat generated by the header without a heat-shield could have caused premature failure in the alternator. They said there is a regulator for the alternator about 3" from the header. They said it may not be covered under warranty if the alternator goes again... Is that BS or what? I was ready to call BS on them if they started making a big deal about it... Does that sound like a legitimate cause of failure?
hey andrew,
i hope it really is your alternator... that is weird that the gauges go one at a time... although i've heard of instances like that before.
Re: *Weird* problem - speedometer dead/acting odd and charging system not working (long)
Quote:
Originally posted by aklucsarits Oh, also, they scolded me about my Mugen header. They said that the excess heat generated by the header without a heat-shield could have caused premature failure in the alternator. They said there is a regulator for the alternator about 3" from the header. They said it may not be covered under warranty if the alternator goes again... Is that BS or what? I was ready to call BS on them if they started making a big deal about it... Does that sound like a legitimate cause of failure?
Yes, your alternator can fail because of heat. Have you seen those big heat blankets that domestic V8 owners use on the starters? It's to keep heat from causing premature failure. I wouldn't doubt that heat could have caused the failure. Whether it did or not is another issue.
It could just be your alternator. Your car will do funny things when there isn't enough juice. Although, I find it strange that you could barely keep it running, but then start it again the next day. I would just let them replace the alternator (very easy), and see what happens from there.
Let me ask you this - How old is your battery? What year is your car? The same exact thing happened to me the other day. Just that I wasn't able to start my car in the morning and check it was a dead battery.
Went and got a new battery a week ago. I haven't had the same problem since. Cross my fingers that it's not my alternator.
OK. Listen to THIS!
The dealer calls me up today and says they swapped out my alternator for the new one, but the car still does exactly the same thing. So the original alternator was fine - (despite the dealer suggesting that the heat from my Mugen header killed it )
So now the service rep says something to the effect of - "Now we think it's your ECU. It probably won't be covered by warranty because you have an aftermarket ECU."
The rest of the exchange between me and the dealer service rep went something like this...
Me: "Ummm... Mmmm hmmm... So if it's not the original ECU in the car, what kind of ECU is it?"
Honda Service Rep: "Well my tech says it doesn't look like all the other Prelude ECUs he's seen. He says it has a chip in it or something."
Me: "A chip, huh?"
Honda Service Rep: "Yeah. It looks like it's been modified. It's not giving any CEL codes, and a lot of the readings it is giving are way off the scale. For example, your heated O2 sensors should be reading around 1, and our diagnostic shows them reading a 3..."
Me: [interrupting] "Well, I can assure you that that is the original ECU that you sold me with the car. And it has not been tampered with in any way by me."
Honda Service Rep: "Yes, but we sold you this car new. And now it has an aftermarket ECU. Someone put it in there..."
Me: [getting frustrated] "OK. I'm sure you guys know a lot more about this than I do... But, honestly, I have *thought* about replacing the ECU. *And* I have actually done quite a bit of research into getting an aftermarket ECU for my car. I learned two things in the couse of that research: 1) You cannot buy an aftermarket ECU for this car. 2) You can not "chip" the ECU that came with this car. It has no "chip" to replace or modify. All of the maps are stored in static SRAM in the ECU's primary microcontroller. I have not replaced, modified, or otherwise tampered with that ECU... It's not possible to do what you are suggesting I did on this car. Do you think maybe the ECU may have just gone bad? That may be why it's giving strange readings..."
Honda Service Rep: "Oh. OK... I guess my tech just hasn't seen any of the 2000 model ECUs. I guess it looks different than the older ones. I'm just going on what my tech said... [trailing off]
Me: [Unnecessarily volunteering] "The only things on that car that I have changed are the header and the exhaust. And I removed the air intake resonator from the fender well and plugged up the vacuum hole to the resonator so that I would not have a vacuum leak..."
Honda Service Rep: "Well OK. I think we may have to try another ECU."
Me: "Do you have any in stock?"
Honda Service Rep: "No. ...Well, we may be able to pull one from a car on the lot to test with. But we will probably have to have the part overnighted from Ohio again. We'll keep looking at it this afternoon, but we may have to wait 'til tomorrow for the part."
Me: "OK, well let me know as soon as you hear something..."
Andrew
Last edited by aklucsarits; 05-31-2001 at 05:29 PM.
They replaced the alternator *and* the ECU. They said it looked like the ECU died and killed the alternator... They replaced the original ECU with a new one, and that cleared it up, apparently... Somehow my ECU had failed.
I asked them if they put the original alternator back on, and they said no. They kept the new alternator on. They still insisted that the original alternator had gone bad - even though, the day before, they replaced it and admitted that it did not fix anything... (shrug)
The alternator charges the battery (duh). What most people don't know is that it usually doesn't do squat until after 2000RPMs or so, especially if you are running with lights, etc. The alternator charges the battery by generating a higher voltage than the battery, thus allowing current to flow into the battery.
If you lose the alternator while driving the battery/charge light should come on. On other makes you can have all sorts of other problems (for instance, in my Isuzu, ALL the lights come on, then the engine won't start if you shut it off). In the Prelude, everything works fine until the battery voltage drops.
As you drive w/no alternator, the battery voltage will begin to drop until items running off of the 12V start to drop off. For instance, the lights will always stay on but will become dimmer as the voltage drops. The radio might drop out at, say, 10V. The cluster might drop out earlier. The ABS computer might drop out afterwards. It all depends on the design of the components which (most of the time) aren't really designed to work well under 12V.
That explains all of that. The ECU business makes me think that the dealer had their head up their ass, as I can't see what the low-voltage condition would have done to harm the ECU.
The premature death of the alternator would most likely have been due to an overload or overheat condition. I've never seen one fail from heat (yet), so I would suspect an aftermarket stereo (amplifier)? Whatever it was, you need to rectify it, or the new one will surely suffer the same fate.
Marcucci, as always, great info! Where were you when I had this problem? If you'll note the date on my post, it's been well over a year since this episode, and my car has been running trouble free ever since they replaced the ECU...
Andrew
__________________
2007 MINI Pooper S
2006 Mitsubishi Lancer Evolution IX SE
2000 Honda S2000
1992 Nissan Sentra SE-R
hm same **** happened to me last night....2000 sh with almost 50k and aem pullies. Same eXACT problem. I bought a battery at walmart for 40 bucks to drive home on so I didn't need to tow the car. I got home fine, now I have to find myself a prelude alternator on a saturday afternoon.
When mine went the ground wire ws beat as well, however that had happened prior to the alternator going. Ive "thought" the problem was from a missing/loose ground wire a couple years back. Once the loose ground wire was replaced the car ran fine so I never thought about replacing the ground from the alternator. The alternator quit and the dealer said it was from the stereo however they replced the beat ground wire at the same time and it's seemed fine ever since.
did you check your ground strap? For some weird reason mine had come loose, so the ground to the alternator wasn't always connected. Had the same crap happen to me Scary to see the gauges go dead and everything go dark
i had that exact same nightmare happen to me this summer. turned out to be a short on my the main wires, feeding my fuel system. on some 50 amp fuse that was slightly shorted, creating large amounts of heat, thus burning all the wires around it in it's, and other wiring harnesses in my car. got it replaced with the help of insurance under 'fire'... it was ***. didnt have my car for over a month while honda kept telling me it was the alternator. but they had no idea wtf they were doing.
Right now im in the same situation, I just ordered a used alternator since im going to be selling the car, but Im worried that it could possibly not be the alternator, I am going to check the fuses tom before I install the alternator. I wish I had the proper equipment to check on the main wires. Anybody have any idea what it could be besides the #15 fuse the helms says to check. ?
__________________
98Type SH Stock-Nordic Mist
WTB: Tanabe SMH Catback
the wire that was fuct on mine was behind the under-armor (that plastic barrier under the car), and then in behind some other crap. up against the transmission. it was shorting on one of the sharp edges on it, due to ****ty installation.
if i were you, i would take it to a trusted electrical mechanic. let him assess it. cus your speedo, tachometer, and head unit all had improper voltage due to the huge draw on the shorted circuit. (this is what happened to me, anyways...) i got mine fixed under insurance, alongside my deductible.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
They said there is a regulator for the alternator about 3" from the header. They said it may not be covered under warranty if the alternator goes again... Is that BS or what? I was ready to call BS on them if they started making a big deal about it... Does that sound like a legitimate cause of failure?
"OK, well let me know as soon as you hear something..."
If you'll note the date on my post, it's been well over a year since this episode, and my car has been running trouble free ever since they replaced the ECU... 
Linear Mode
