Question about 1991 Mercury Grand Marquis
I just changed the alternator on my 91 Grand Marquis. That should have taken care of my problem with power supply. The battery was tested and said to be good. Now the darn thing just keeps on stalling, whether after using the brakes around a turn, or just simply at idle at a stop. The battery light was off after new alternator put in and once again it has come back on. I don't know that much about cars, but I sware this car has a ghost in it or something, just stealing my power and functionability. Should I get a new spark plug, or spark plug wires etc.? Please help me, I am completely lost.
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.
i hope i was able to correct your problem.
Posted on Jul 08, 2008
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