I have a 93 civic with a 70 amp alternator. Right now the alternator is producing too much voltage( up to 20 volts) I suspect that my 900 watts rms stereo system(mtx tc 4001 front chan. @ 4 ohms rear chan. @ 2 ohms, mtx mxa6001 A 2ohms) is to blame. So I decided to get a HO alternator, but the closest guy that does it is in brampton a few hours drive. After doing some homework I found out that added a second isolated battery may provide better protection. Does anybody have any advice, pros or cons and what would you do? HO aternator, Second battery or both? I have already upgraded my battery and wireing for those who will ask.

how is the alt being measured at outputting ~20v?

Hook up DMM to starting battery terminals with vehicle off.

Now reconnect the probes after starting the battery and see what u get at the battery's terminals.

If you still get close to 20, or anything over 15.0v, stop driving the car until you get the charging system taken care of.

IT may be a damaged regulator unless your alt is internally regulated.

sorry forgot to mention. Its an intermetent problem, yes it was measured with a DMM it fluctuats between normal and 20v. It does it at idle or at 2000rpm. It does it with everything on (lights,ac,defrost,stereo) or with everything off. Is it possible that my cap is defective and causing some sort of a problem? the alt is less than a year old and I would assume its internally regulated but not sure. how do I check?

Edited July 18, 200817 yr by idlewild