Mercury Repair Questions? Ask a Mechanic for Answers ASAP
Thanks for choosing Just Answer! If you have a charging system fault it is possible to have different monitors read incorrectly and set false codes or lights on the dash. Does the vehicle restart after it dies? And can you get the battery light to go away if you rev up the engine to around 2,500?
The alternator most likely is at fault for this concern since the lights go away, it is possible that the regulator of the alternator is not keeping up and killing the vehicle, typically for this scenario to be present the battery is slightly weak and cannot keep the engine running but has enough charge to allow the vehicle to restart. Run the vehicle, turn on the A/C on and the blower motor to full speed, turn the headlights on and the radio (volume doesn't matter but may turn on enough to allow sound through the speakers to increase the load), Run the vehicle for around 15 minutes and see if the battery light comes on, if it does the alternator / battery should be replaced / tested as needed. If you had access to a volt meter or a charging system tester it may help for this type of issue to find the exact cause of fault, also if there is corrosion around the battery this is a sign of the battery being weak.
What condition are the battery terminals in and do you happen to have a volt meter?
If you turn the volt meter to the 'V' position, you would then put the red lead on the battery + (positive / red) and the black lead on the battery - (negative / black), the voltage reading can help to determine the charging system status. At times it takes a load tester to fully test issues like this, and usually its the regulator that causes the fault.
At this point, we will need to check the alternator with a voltmeter, the testing can be done at the battery. Id suspect that the alternator is the issue, being you don't have a check engine light present.
If the engine shuts down due to lack of voltage, the oil light and other lights that you see when the key is in the run position will be on. Other cause would be something is loose like a ground wire but generally the vehicle will not restart unless the wire is sitting just right.