ck279

I recently put in a new alternator which I think is defective. I would like to test it to make sure it is putting out the proper amount of amp's as well as volts. Using a multimeter can it be tested with it in the vehicle and if so, how?

spyder

Easy test. Start the car with the battery connected. Once it is running, pop off the battery clamps. If the car keeps running, the alternator is working. Make sure and rev it up while doing the test, sometimes they will idle with an under-powered alternator but not rev up high.

ck279

Thanks! But is there a way, using my multimeter, or another instrument, that I can find out exactly how many amp's I'm putting out?

Rodney

yeah, use a voltmeter at the battery. you will have 12v with the car off. then start it, and you shuld have 14.4 or so at the battery. that would signify that the alternator is working. good luck.

fixhondas

neither of these tests will tell you if the alternator is worth a damn- you need to measure the current the alternator produces- to do this you need an electrical load and an ammeter- you also need to check the diodes- you can do this with a charging system checker or an oscilloscope. Unhooking the battery while your engine is running is NOT a good idea- if your voltage regulator is bad and sending too much voltage- you can cause damage (although I have seen Passports survive 18 volts- but they are made by Isuzu). What kind of alternator did you get? What kind of problem are you having. You can use a voltmeter to see what your voltage regulator is doing- with the engine running it should be around 14.0-14.6 volts. Most aftermarket reman alternators are garbage- you would be better off to get one from a junkyard or get one from your Honda dealer.

ck279

Thanks, that was the reply I was looking for. I got a remanufactured alternator from PepBoys. My OEM one put out voltage and some amp's, but they were very low and barely supoerted the electrical system. It was bench tested and confirmed defective. The PepBoys unit had a lifetime warrenty so I said what the hell. From what your saying Rodney I cannot check the amps with my multimeter right? I just want to test it with it in the car, but PepBoys wants $18.00 for an entire electrical system test. That, or take the alternator out to test. Those ******* will not test just the alternator for free with it in the car....bastards. I wouldn't mind just jackin it up and taking it out but with my supercharger the clearences are really tight and it is a much more involved affair. I don't have an o-scope. I might end up getting one from Honda if this continues. BTW, the problem is that my check engine light goes on and off. When driving with no accessories on it rarely lights. When my winshield wipers, audio system (pretty small), headlights and fog light on it will almost stay on completely when I am out of gear at idle. When I am in gear driving it never lights. Sometimes even during shifts it will blink as I shift. Everything in my car works fine too. You would assume that my headlights would be dim or blink while my system is on.....nope. One question: I recently hooked up an Autometer voltage gauge. It shows my voltage to be about 12.5 when idleing and about 14 when in gear....is that right? I know the charging system goes above 12 V when in use, but I thought this would apply when idleing as well. Help me out here Rodney....what do you think?? Thanks!!


[Modified by ck279, 9:36 PM 10/12/2001]

fixhondas

your check engine light goes on and off or your charging light?