Car: 1993 Civic EX - Manual Trans - 1.6L - D16Z6

I have a voltage gauge wired up so that I can monitor it. It was steadily at 13.5 volts or so for a year or so (which is standard) and now when I an out of gear or idling the voltage will drop to 12 volts or even 11.5-ish volts. It returns to 13.5 if I rev the engine but returns back down we the throttle is released.

This may or may not be relevant but I have been hearing a faint whistling, like that of a supercharger, sometimes. My thought is a slipping belt but it seems that the deflection in the alternator belt is okay. So maybe bearings?

Are our alternators multi leveled? As is, are there multiple levels of charging?

What are things I should look for?

Thanks!
Dan

 

how old is your battery?

 

my guess is that your voltage regulator is starting to go. eventually your battery will not get recharged. you can have the alt bench tested to be sure.

 

Make sure it is the same load as before. Voltage should stay up at idle with just the engine on, but it is normal for it to drop at idle with any major electrical load such as the A/C, defogger, etc. Also note the radiator fan as it starts and stops automatically and is a considerable load when on.

The ECU can command the alternator to drop to 12 volts to reduce load on the engine, but I don't know under what circumstances it does. I think that those circumstances are rare.

 

The battery isn't that old. I think 3 years at the max. I'm probably going to take the car to Advanced Auto since they do a battery test. I'll see if that yields anything.

I didn't think that the EG's had a voltage regulator?

 

all vehicles have a voltage regulator,some 80's and up have them built into the alternator and old trucks/cars like 80's and older have dont have them in the alternator its a seprate module,

 

at idle i wouldnt worry about it to much BUT if you just want alittle more power at idle then i would suggest a overdrive pulley for the alternator... only downfall is you will have to make a new upper adjustable arm to keep your stock belt.

the overdrive pulley is smaller so it needs a smaller belt OR more adjustment that the stock arm just doesnt have. very easy to make your own tho. i did. simply buy a alternator adjusting arm and cut it shorter and drill a hole in it to mount it where the stock adjustment arm is...
this is mine.







the charging system sucks at idle on just about any vehicle unles you have a high idle

but the whining noise... well hard to tell unless its a constant whining and then still only be able to notice if you pull the alternator and have it bench tested...
2 other bearings it could be is the acs tensioner or the timing belts tensioner pulleys.

and yes every alternator ever built has a voltage regulator.. either internal like in old school vehicles or internal like every newer vehicle.
external regulators suck! i constantly had problems with my old 66impalas external.... so i upgraded it to a internal regulated alternator and never had any problems after then.

 

It ending up being the alternator. Please check my build thread for the whole story:
https://www.hondacivicforum.com/foru...=64281&page=44