Rep Power: 0

Whats the best way to test our alt to make sure its voltage stays above the required output? Im going to get a friend to do it since hes already looking at my car tommorow. What do i tell him? I can say test the alt but do what exactly what kind of test?

 
Rep Power: 285

Hook a voltmeter to the positive and negative contacts and read the output, simple as that.

 
Rep Power: 0

Does the car have to be running? What numbers shiuld i be looking for?

 
Rep Power: 812

if you mean amp output, go to most auto store and have them do a free alt check. they have the big machines that can read amp load. voltage will be around 14v if you just take a reading at the battery with a multimeter. not really useful for anything because the alt may only be producing 30 amps yet still read 14v at the battery.

 
Rep Power: 0

well i was told theres a certain Voltage that the alt should always be above when the cars running....is that true? Is it 13.8? ill try to find the link. It said something like if it ran too low, then it would put extra strain on your trans and engine.

Heres a quote

Voltage drop is the most obvious culprit where alternator-related transmission woes are concerned. If your alternator's voltage stays consistently below the required output, the transmission may alter programming to keep the engine rpm low to reduce load on the engine. Alternatively, some transmissions may have programming to lock the engine into a lower gear than it should to raise engine rpm and alternator speed with it. Most of your transmission woes probably have more to do with a programmed strategy than an incidental failure.

 
Rep Power: 285

The engine and transmission suffering any serious side effects as a result of poor alternator output is quite a stretch, some people who want to save weight and reduce parasitic power loss actually remove their alternator and upgrade to high end batteries. Besides, on our cars I'm pretty sure the battery light would come on before anything that quote describes would happen.

Good tip on having the autoparts store check the amperage, Gear. I've always been told to just monitor the voltage output.

 
Rep Power: 235

Low voltage won't damage the trans, at least not in this car. It could damage the ECM/PCM or MCU though. They need a minimum voltage to work correctly. When talking low voltage, it may seem like the trans (auto) is messed up but, it's really the ECM/PCM.

ECM/PCM= Engine Control Module/Powertrain Control Module

MCU= Multiplex Control Unit

 
Rep Power: 291

Using a multimeter doesnt tell you anything except whether your amp is working or not, and your battery is holding a charge or not

You batt may read 13v , but not start your car because your CCA has dropped to like 100

 
Rep Power: 812

there are several issues here. first, alternator's main job is to charge the battery. there are many guys over at ecomodder running without alts at all, just a couple of hi power batts that they charge up each day. so long as the electrical systems are getting their 12v, they will be happy. too much or too little and you start to strain electrical parts. batteries are way more complicated that most people think and the average person has no idea how to even use and maintain a battery properly.


as for the alternator, sometimes it runs at 14v, other times at 12v depending on what the ELD decides it should be. if youre driving with no accessories on, chances are you will be at 12v. crank the fan on a few clicks and the voltage goes to 14v to balance the extra power draw.

 
Rep Power: 0

14.3V thats the reading we got, while the car was running, used a volt meter. As for checking how much amp output its putting out i called a shop and they said you need a special adaptor to connect the alt to on hondas and they dont have it so ill call around.

Like you said, the shop said the same...even though the alt reads good in voltage, it doesnt mean its outputting its max amperage.