9/4/08 11:45 a.m.

Question? I drive a 89 Honda Civic SI, the problem I'm having is the battery is overheating/smelling this is the 2nd battery in a shor time. I've read this could be caused by the voltage regulator and/or the ground wires. Can anyone give me some input. Thank you in advance.

Dr. Hess
Dr. Hess SuperDork
9/4/08 12:49 p.m.

What's the voltage across the battery when the motor is running at around 2-3K RPM?

pinchvalve GRM+ Memberand SuperDork
9/4/08 1:33 p.m.

Don't undersetimate the ground issue. That should be step #1: remove each ground and clean it and make sure it is a solid connection. Unplug any plugs between the battery and ground and engine and ground and make sure that they are good and making contact. Then move to step #2.

Step #2 is listen to Dr. Hess. Seriously, hear that? It's my car running. (OK OK, with a 16v not a 20v but still...)

Jensenman SuperDork
9/4/08 1:45 p.m.

Sounds like an overcharge issue for sure. Normal battery voltage at Doc's 2-3K RPM is around 13 volts, give or take. Anything over 14V would make me start looking real carefully.

Back in the Dark Ages (the '70's and earlier), a common cause of overcharging was a ground strap missing from between the engine and the body, people would just throw them away because we all know the grounds are not important, right? Most cars now have a negative cable which goes from the block to the body and then to the negative battery terminal. If someone took the center mount loop off the body to install a bigger battery or one with the terminals in the wrong place, that'll do it. Another symptom of this: the throttle cable and any other small diameter connection from the engine to the body will get hot because they are acting as grounds.

Quick test: with the engine running and the headlights on, connect a jumper cable from the battery negative post. 'Tap' the end of the wire on something metal on the engine. If the headlights flicker, brighten, dim etc when you tap the wire then there's a ground issue.

If all that's good and tight and clean but the alternator is still overcharging, chances are the alternator's voltage regulator has crapped out, meaning a replacement alternator.

Woodyhfd GRM+ Memberand HalfDork
9/4/08 4:53 p.m.

I put 300,000 miles on my 89 Civic Si. I sold it about seven years ago and I still miss it. If they still made them, I'd still be buying them.

Anyway, if I recall correctly (I may not), I think that they used an internal voltage regulator inside the alternator, and a new alternator was the only option.

I added a cheap voltmeter when mine started going through batteries at an alarming rate. It helped me discover that I was buying crappy rebuilt alternators.

Sonic New Reader
9/4/08 8:16 p.m.

Yup, Civics have the voltage regulator as part of the alternator. Try replacing that first.

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