I have a bone stock 1998 Civic EX automatic with 249,000 on the clock. I have been having problems with the speedometer jumping all around and the SRS and battery light flickering on & off. I checked the voltage at the battery while running and under load and it was reading 16 volts, so I replaced the alternator. Now it reads normal 14.3 under load. I've already decided that the VSS needs to be replaced (fix for the eratic speedometer) and also the #15 7.5 fuse has not blown. But after replacing the alternator, I still have a problem with the headlights getting bright and dim. There also seems to be a clicking sound from under the hood when the lights get brighter. But the SRS & battery light problem has been eliminated and the check engine light hasn't come on. Thought that replacing the alternator would correct the light surging problem, but it hasn't. I've checked all the grounds that I could find including the battery to chassis and they are all good & tight. I'm open to any suggestions as to what the problem could be.........

 

....lots of good info in this post:

Headlights bright then dim. ELD or "loose" regulator??? - Page 2 - Honda-Tech

 

Get under the car and inspect the wires for any fraying. Fuse 15 doesn't always blow.

 

I'll have to jack it up and get under there and check. Some other info.......drove it about 60 miles tonight. There's NO clicking. The headlights and the dash lights are all affected. It only does this between 2 & 3000 rpms while driving; can't get it to do this while sitting and holding the motor revs at 2500........and the change from dim to bright is very abrupt.

And for an update (4/22),.......it's now doing this sitting at idle and starts immediately after start up.

 

Well, finally got the car up on jack stands. Got under there and removed the intake manifold brace and found nothing. NO rubbed thru wires at all. Checked the #15 fuse and not blown; and I still have the surging light problem. Now I'm really at a loss; thought sure that would be the problem......I'm open to any suggestions.......

Last week I replaced the VSS sensor & the speedometer's still jumping around like a tach.......very frustrating.....the original one probably wasn't bad......I'm beginning to wonder if there's not something wrong in the instrument cluster itself that could be causing this???

 

So far I have:

Replaced the alternator
Replaced the VSS
Checked the VSS connector for corrosion with none found
Checked the main grounds & chassis ground from motor to frame
Checked the #15 fuse with a test light to verify current
Removed rear manifold brace & inspected undamaged wires; no rub thru
Cleaned both battery terminals and connectors
removed gauge cluster and tightened all screws on the rear
Inspected wires and grommet at the rear 02 sensor; no damage
Checked all connections at the alternator

I am wondering what else to check. I'm still having the surging light and crazy speedo problem. Any suggestions would really be appreciated!!

I wonder if a cell in the battery going bad could cause all of this??? The battery seems to be fine, but that doesn't mean that a cell could be going south......just a thought.

 

Take the grounds off and clean them to be sure well grounded. Measure for voltage difference between engine and battery (-) post while running. Do the same thing for the frame / body.

Your new alternator could be bad. Also make sure the plug with small wires to the alternator is not loose or corroded. If the "I" wire (black and yellow) does not supply battery voltage to the alternator, the alternator will not put out a steady voltage.

 

Just checked the plug; nice & tight. Removed it and there are no corrosion issues. I'll check to see if this alternator is bad, but I have a hard time believing an alternator new out of the box is bad, but I guess that anything's possible! Before I replaced the previous alternator, I had issues with the SRS and battery lights coming on & off; replacing the alternator corrected that problem. If this alternator's bad, wouldn't I be having the same issue?? And the entire time I've been having this problem, the CEL hasn't come on.

and thanks for the response BTW!!

 

Had the battery (bought 9/10) checked and it had 2 cells that were going bad; replaced the battery and now I'm still having the light surging problem. Checked the voltage at the battery and it's holding between 13.2 and 13.5 no matter what the load is. Even with all of the accessories on including the lights / AC, it goes no higher that 13.5. 12.6 when the car is off. My next move is to replace the 2 week old alternator with another one. Fun fun......not an easy task on these Civics........

What is the normal alternator output when the voltage regulator is on? Over 14??

Found this; guess it's time to change the alternator......



"Check the voltage at the battery with the engine idling and look for 14.5 volts plus or minus .8 volts. Turn on the headlights and the air conditioning and watch the voltmeter to make sure the voltage does not drop below 13.8 volts. If the voltage observed was less than these parameters, one or more of the diode banks are bad and the alternator needs to be replaced"

 

Have you confirmed that battery voltage is delivered to the black and yellow wire on the alternator with the key on?