While driving the other day I noticed that my dash lights and head lights started to dim. It acted like the alternator was starting to go, but when I revved the rpms back up the car would come back to life. So then I thought it must be the battery. My truck has the same battery as my xfire so I swapped them out, but it didn't fix the problem. Tested both batteries and they're both holding steady at 12 volts until I start the car. Instead of reading 14 volts right after starting, the voltage quickly drops and ultimately the car dies after idling for a while. Is there a relay I should check or do I have a bigger issue?

 

Most likely the alternator ....

 

Ditto; use search under "alt. problems

 

battery is suspect if below 12.6 with no load.
battery is suspect if below 10 volts during starter operation.
Alternator is suspect if voltage at battery is less than 13.8-14.5Volts with car running.
Get someone to do a load test on the battery, quick and easy.
In the old days, I would have said to check the fan belt tension!

 

My alternator died recently and looking back, it was weak and giving me signs for a while. If you have a multi tester, set it to 20 volts and check the battery voltage with the car off. Red to positive and black to negative. Start the car and check again at idle. If it shows the same voltage or less with the car running the alt is DEAD. If the voltage goes up some but not much at higher engine rpms, it's weak and dying and only charging the battery at higher rpms and not at idle.

Naturally, the easiest way is to have a auto parts shop test it for free. I just feel funny trusting someone that wants to sell me what's being tested.

Les

 

I felt the same way about my dear wife before we were married ........

 

………. no comment ………… biting tongue …….. too easy …..