Alternator issues.

[selmerguy]

I am having problems with my alternator I think. Driving my car the other day it died. I jumped it and it died again. I was close to my house so I parked the car and took the battery home to charge it. In the morning I put the bat. in the car and it started fine. I drove it home with no problems and when I pulled the positive cable off the battery the car ran fine. I was puzzeled so I shut down the car. Then I restarted it and pulled the positive cable again and the car died. It is like the alternator works when it wants to. I took the stupid thing off today and took it to get it tested and it passed. I do have a external dump but it does not dump anywhere near the alternator? I am going to make a heat shield for it and see if it helps. Any ideas on what my problem is?

 

[DGajre777]

Do you have a voltmeter or a multimeter to see when it is charging the battery and when it isn't while you drive? A good alternator should read between 13.6 to 14.2 volts depending on load, like A/C, headlights, audio system, etc. If your volts go down to 11.8 or 12.v, then your alternator is bad.

Do you have a heat shield for your exhaust manifold?

Also, you might need to check on this, but I remember reading something about frying the ECU if you pull the power cable from the battery while the car is running.

 

[steve]

Also, you might need to check on this, but I remember reading something about frying the ECU if you pull the power cable from the battery while the car is running.

You sure can. You can blow the alternator too. Best way to test is with a voltmeter like you said.

Steve

 

[selmerguy]

wow you leanr something everyday. the problem is that the alternator seems to charge only when it wants too. I have a cap. in the trunk with a guage on it. No i dont have a heat shield with my exhaust.

 

[DGajre777]

Have someone monitor the voltmeter and see if it charges above a certain RPMs. Mine did that with my old alternator, it would only charge above 3000RPMs which was a bad voltage regulator. I got a new rebuilt Mitsubishi alternator from the dealership last month and all is well.

If you have a multimeter you can set it to 12v and temporarily wire a power and ground wire from any source (even your cig lighter) and have someone look at it while you drive.

 

[steve]

Datalogger does that quite well

 

[selmerguy]

I put the alternator back on today and the car syarted fine. The thing charged 14 volts at idle. I shut it off and turned tha car back on and I only tot 11.8 volts. It just charges when it wants too. I am going to buy a new alternator with a warenty and see it my exhaust setup is hurting anything or if it was just time for that alternator to go.