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98 Civic - Possible electrical problem?
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#11
 
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Re: 98 Civic - Possible electrical problem? -
03-29-2007
, 04:50 AM
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I've had an intriguing issue with my 98 Civic, and thought I might describe it here, and see if anyone has some insight as to what could be going on with the car. Short story: poor fuel economy, alternator test suggests bad alternator (175 amps?!?!), occasional dimming of lights, otherwise no problems with the car. Long story: I've had the car for about 3 years, and it's always been reliable, except last year when the speedometer started acting crazy, and the transmission shifted rough. It turned out there was a TSB for a wire bundle that would run on the intake bracket, causing a fuse to blow, which caused the other symptoms. This is the TSB: http://downloads.hondatech.info/Auto...n/x99-029e.pdf Anyway, I checked that wire bundle and couldn't find anything wrong, so I just replaced the fuse, and the car was back to normal. Both before and after this incident, I noticed that the lights (dash, headlights, dome light) would sometimes flicker or dim, but it was completely intermittent. I took the car to AutoZone to get the free battery/alternator test, and they told me that the alternator was bad, outputting 175 amps! I don't know if that was the measurement under the tester's load, or what, but the alternator is only spec'ed at like 80. I thought that maybe there's a wiring problem that may be causing a load on the alternator all the time, hurting my fuel economy. (I "only" get 25 miles per gallon) If anyone has a suggestion, I'd love to try to figure out what's going on. I'm handy with a multi-meter, I just don't know where to start. Thanks in advance for any replies. -Randy |
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http://www.carkb.com/Uwe/Forums.aspx...-cars/200703/1
#12
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You must be using an analog voltmeter, which reads like that on AC ranges. snip All digital voltmeters work right. Nope, it's a digital multimeter, but admittedly a dirt-cheap (sub-$10) one. Still, I guess I should have realized that it was probably just doubling whatever voltage it saw, hence that reading. More in a reply to "jim beam" later in this thread. Thanks again for your time and response! -Randy |
cars and they may do the same. I ought to check. Thanks!
Mike
#13
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#1. learn how to use a meter properly. you do /NOT/ measure a dc voltage with the meter set to ac. Before I go any further, I want you know that I'm grateful for your help. That said... I'm pretty sure I know how to use a multimeter. My intention was NOT to learn the DC voltage, but rather the amount of AC ripple, which exists in any DC generated by a rectifying circuit. Obviously, since I measured pretty much the same thing on another "good" vehicle, either my meter was wrong, or I'm not using it right, but I'm going to blame the sub-$10 digital multimeter, unless you tell me there's a different way to measure AC ripple on a DC voltage. #2. suspect a crock from autozone. there's no way an 80A alternator is going to output 175A, even intermittently. I'm leery of what they told me, but I'm confused as to how two different stores, 6 months apart, managed to measure the same thing, and make the same diagnosis. I'd believe you over them any day, but I'm still curious as to what they're measuring... |
the windings. http://tegger.com/hondafaq/altcharge.html Maybe the regulator
is running wide open? I'm grasping at straws here.
I'm sure your situation is frustrating, but you're providing some
interesting glimpses into the "shouldn't work that way" areas :-} As Mr.
Spock would observe in the old Star Trek series, "Fascinating."
Mike
#14
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randyoo (AT) gmail (DOT) com> wrote in message news:1175121753.078339.8680 (AT) b75g2000hsg (DOT) googlegroups.com... ... By the way, I measured 30 volts AC across the battery with the engine running, and then went and measured another vehicle, and got nearly the same reading, so I assume that most likely, that's a normal reading. I admit I never thought to measure AC across a vehicle battery. The alternator is supposed to have diodes in it, which filter out the AC, but I suppose you are going to get some fluctuation with the alternator making output. What is the DC voltage? Earle |
True RMS meter. 30VAC seems odd.
DCV is more important,though.
--
Jim Yanik
jyanik
at
kua.net
#15
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With regards to your crazy speedo, I had the same problem recently on my 98 Civic LX. Here are pics of what I found was wrong. The short blew my #15 fuse, which is for the Alternator and BOTH O2 sensors. |
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If you've been driving around with this fuse blown, it would make sense that your mileage is in the pooper. My car runs like a top now, mileage back to high 30s. (and it has almost 300k kms on it) Pics have been uploaded to http://www.tegger.com/hondafaq/misc/..._mil%26fuse15/ t randyoo (AT) gmail (DOT) com wrote: #1. learn how to use a meter properly. you do /NOT/ measure a dc voltage with the meter set to ac. Before I go any further, I want you know that I'm grateful for your help. That said... I'm pretty sure I know how to use a multimeter. My intention was NOT to learn the DC voltage, but rather the amount of AC ripple, which exists in any DC generated by a rectifying circuit. Obviously, since I measured pretty much the same thing on another "good" vehicle, either my meter was wrong, or I'm not using it right, but I'm going to blame the sub-$10 digital multimeter, unless you tell me there's a different way to measure AC ripple on a DC voltage. #2. suspect a crock from autozone. there's no way an 80A alternator is going to output 175A, even intermittently. I'm leery of what they told me, but I'm confused as to how two different stores, 6 months apart, managed to measure the same thing, and make the same diagnosis. I'd believe you over them any day, but I'm still curious as to what they're measuring... #3. check the brushes on the alternator. they're cheap to fix. the rest of the honda alternator is good for 300k miles very often. #4. re mileage, check for gotchas like brakes stuck on, dying oxygen sensors, etc. This is great advice. I never even considered the brakes/O2 sensors, either of which could be faulty by 150k miles, and would definitely impact fuel economy. Hmmm, O2 sensors... Maybe that cheap-*** multimeter will come in handy, after all! At least I know how to get DC voltage readings from it, for sure!  Thank you again for your time and help. -Randy |
--
Jim Yanik
jyanik
at
kua.net
#16
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With regards to your crazy speedo, I had the same problem recently on my 98 Civic LX. Here are pics of what I found was wrong. The short blew my #15 fuse, which is for the Alternator and BOTH O2 sensors. Wouldn't that turn on the CEL and set a code or two? If you've been driving around with this fuse blown, it would make sense [quoted text clipped - 43 lines] -Randy |
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http://www.carkb.com/Uwe/Forums.aspx...-cars/200703/1
#17
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i doubt a meter that cheap will give you ripple since it'll need to "offset" the dc. |
read the ripple on top of a DC voltage. On the AC setting, the input
signal is AC coupled (through a capacitor).
Regardless, both the poster's car and a known good car measure 30V
ripple. This simply isn't so. There is something wrong with the meter or
the method.
<snip>
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in the mean time, measure the dc voltage at idle, no load and at idle, full load. if the readings are within spec, it's probably just brushes giving you that startup flicker. also, check the gotcha of belt tightness. |
the voltage regulator is lowered while at idle (if a few other
conditions are met). Bumping the RPMs up a tad from Idle makes the set
point return to 14.5V (nominal).
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