I have a 1978 115 mercury outboard that is putting out to much voltage to the battery. the voltage is 15.9 volts at the battery. i changed the rectifier, but that did not cure the problem. anyone have a solution.
a 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of.(from cars to computers, handyman, and even drones)
click here to download the app (for users in the US for now) and get all the help you need. Goodluck!
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
Get a load test on both. There are 2 components to checking the system voltage and amperage. You can have good voltage but low amperage which will cause issues. 12.75v is low. A battery fully charged should be closer to 13.8v and charging should be around 14.4v
May be but I doubt it. The alternator is not putting enough power to keep the light out. IT works like this battery power (12 volts) flows through the light to the alternator and puts it on when the alternator starts to charge the extra voltage from the alternator (14.5 volts) flows back through the light and as the 2 volts difference is not enough to make the light work it goes out . IF you are measuring 12 volts at the battery and 12 volts at the alternator then then the alternator is not charging. What you should have is 12 volts at the battery and as you rev up the engine the voltage should increase at the battery up to 15 volts maximum at around 2000 RPM
It's best to relate symptoms to narrow things down. I assume you are still getting a dead battery when trying to start even after replacing the alternator and battery. Get a volt meter. Harbor freight sells them ridiculously cheap (about $5). Measure the voltage at the battery terminals when the engine is running. If it is at least 13.5 volts to 15 volts then the alternator is charging correctly. If it is 12 volts then the alternator is not charging the battery.
If the alternator checks out ok, then check for things that could be draining the battery when the car is off. Usual suspect is the trunk light. Put your cell phone on video record into the trunk facing the light, then shut the trunk. If the light stays on, its because the switch in the latch mechanism is faulty. WD40 might make it work, or just pull the bulb. Also, check the glove box light the same way. Good luck...Chris
Sounds like you may have a bad alternator.Put a volt meter across the battery posts.A fully charged battery should read 12.6 volts.Then start the engine and the voltage should increase to 13.5 to 15 volts.If you do not get this increase in voltage, then the alternator is not charging, which can be either the wiring to the alternator or the alternator itself being bad.Good luck :O)
Take a volt meter and put the test leads on the battery terminals,
red to positive,
black to negative,
set meter to 12 volts dc
If the meter reads less than 14 to 15 volts dc, the alternator is not charging and needs a new one.
With volt meter on battery start car and read voltage. When yo first put the meter on a full charged battery it should read between 13-15 volts. When you first start motor the voltage should go 3-4volts higher then when you first put it on. And then tapper down after awhile. If there is no voltage increase after start alternator is out.
first check battery voltage. should be 12 volts or a little over. IF the battery is low then charge battery and then load test battery. If you remove you battery and take it to local parts store most will check for you. if battery load test good but was low on voltage then I would check to see that alternator is charging while engine is running. should be charging aprox 13.9 volts. if battery had full voltage and load tested good then most likely the starter is bad.
A 12 volt battery is actually 13.2 volts fully charged. If you are reading 16 volts, you are probably getting extranious voltage from the system somewhere, especially if the vehicle is running when you check the voltage. The alternator will put out about 15-18 volts to charge the battery normally, and yours may put out 28-32 volts to charge them in series, but the batteries, when disconnected, should never read more than about 13.2 volts each. Typically, it will read about 12 1/2 volts when disconnected. COMPLETELY DISCONNECT BOTH OF THE BATTERIES. If you still read 16 volts when it is disconnected, you must have a bad meter because the battery can't produce that much voltage, no matter what. (Six 2.2 volt cells connected in series inside the case.) Put the meter on a known good battery on another car that is not running and see if you get the same reading. It sounds like the other battery is almost dead, regardless, and it sounds like your series/parallel switch may be malfunctioning. (That is the switch that puts the battery in series to run the 24 volt starter, then puts the batteries in parallel to run the remainder of the vehicle on 12 volts. This is all assuming that you have a diesel vehicle with a 24 volt starter and that is why you have two batteries.
you do have a short in the electrical system, test this by putting a freshly charged battery and connect the negative to the battery then try to just scratch the positive wire to the battery and watch if there is a big spark that would be produced. if there is then you have a short that is draining your battery. if there is a small one . that could just be your clock or radio. if you have an ammeter ( a tool to measure current) you can take the current that the car is drawing as you put the positive wire to the battery.
another test is start the car. get a volt meter that would measure dc voltage in the range of 20 volts. then measure your battery voltage. it should read at least 13.8 volts dc. turn on your head light, it should still read at least 13 volts dc. then lastly, tun on your ac if you ahve one. it should still read above 12 v. at least 12.5 v. that means your alternator is charging.
all of the test and readng are on idling state.
then rev the car to 2000 rpm if you have an rpm meter and all of the voltage should increase a little bit but not exceed 15 volts.
if it does exceed 15 volts then you have a bad regulator that fries batteries.