wont stay running please help

[mike1oatman]

i have a 98 taurus on day it wouldn start so i hooked up a new starter and it started, then next day battery light was on unhooked the battery and the car died so i put new alternator on it, started driving home and about 30 min later the car started losing pwer lights shut off and car died had to be jumped and only ran for little bit after that so i bought a new battery and had it put on and it is still dieing on me i unhooked the battery and car died with the new alternator on it so i took and had it tested and it came back good, any help would be appreciated, thanks

[shorod]

Welcome to the forum!

Pulling a battery cable with the car running IS NOT a good idea on modern cars. The battery acts as a large capacitor, filtering the noisy rectified power from the alternator. When you take the battery out of the circuit, all that noise makes it to all the computer and electronic equipment within the car. It is possible that this could damage the electronics, but generally the designers incorporate some basic filtering in the electronics to reduce the likelihood of damage from noise. Regardless, the car stalling when the battery was disconnected does not tell you if the alternator is working or not since the stalling could be due to the drop in filtered power available to the electronics.

That being said, a better, relatively easy way to test if the alternator is working is to measure the system voltage under varying loads. Do you have access to a multimeter and understand the basics on how to use it? It would be even better if you have an oscilloscope the also check for ripple and noise, but I understand those are less common and much more expensive.

-Rod

[mike1oatman]

i dont have either one of those tools. but the alternator is new on it and i took it off and took it to a parts store and had them test it and it came back good

[shorod]

Right, but to determine if it is working properly on your car (connected properly) you will need a meter to identify that. Also, if the system voltage drops quickly after the car sits, you could use the meter to identify the drain on the system. A digital multimeter will help you troubleshoot so many issues with your car and home, it's really a good tool to have. With some patience, you could confirm if the starter is working or not, if the alternator is working, and if the battery is healthy. And, if there's a Harbor Freight tools near by, you can probably pick up an inexpensive meter for less than the gas will cost you to drive there. I'm not trying to be a jerk here, but if you cannot make a few simple measurements, it's going to be quite difficult for us to offer much help.

-Rod

[mike1oatman]

im going to buy a multimeter now ill post on here later what i get

[mike1oatman]

i bought a multimeter, innova 3306, but i dont know how to use the thing? how do i use it?

[mike1oatman]

i hooked the multimeter up before starting it and it read 13.06, then started it and tested it and it read 12.56, then turned it off and it read 12.93

[shorod]

If you're seeing 12.56 Vdc at the battery when the engine is running, the alternator isn't charging. It should be keeping the battery somewhere between 13.8 and 14.4 Vdc. Since the bench test of the alternator claimed that it's working, you should double check the wiring to the alternator to make sure it's connected properly.

-Rod

[mike1oatman]

alright double checked the wiring it is on there properly, i dont knowif it helps but the battery only drains if the car is running if the car is shut off it doesn drain the battery?

[mike1oatman]

i thinkl i figured it out i believe it was the mega fuse for battery and alternator it was blown

[shorod]

Awesome! Please report back once you replace the fuse and let is know if that took care of it. Good job finding that blown fuse!

-Rod