Electrical or alternator problem

BRANDON03

MEMBER
2007 MERCURY MARINER
3.0L
V6
4WD
AUTOMATIC
140,000 MILES

My wife and I own the vehicle listed above. This problem happens about every other week to every week only happens once. I will start the car then after I say about two or three seconds the lights radio and dash gauges shut off, headlights don't work either do taillights. The battery light will come on. The dealership said that it was the battery I had that replaced and now they say it's the alternator but I don't believe them I took it to a local mechanic and he tested the alternator nothing is wrong. Could it be the regulator inside the alternator or a electrical problem?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi and thanks for using 2CarPros.

There is nothing in the alternator or battery that will cause everything to shut off. If the alternator stops charging for a second, the lights will dim but not shut off. If the battery is weak, you would be able to tell when starting the vehicle.

With that in mind, this is an electrical issue. The first things I would check are grounds, make sure the battery terminals are clean and tight, make sure the main ground from the battery to the engine and body are clean and tight.

I have attached a partial schematic which indicates the locations of the battery grounds. Check them for condition, corrosion, and if they are tight.

Do this and let me know what you find.

Joe

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Friday, February 1st, 2019 AT 2:46 PM

BRANDON03

MEMBER
3 POSTS

Did not see any corrosion and the wires are tight.

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Friday, February 1st, 2019 AT 3:17 PM

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Okay. Next I want you to check fuse 17 ( amp ignition fuse) in the under hood fuse box. Also, check the PCM relay in the same under hood box. I attached a picture of the fuse/relay box. Check both of these items to make sure they are tight, there is no corrosion where they plug in, and if there is another relay with the same part number, switch it with the PCM relay to see if that makes a difference.

Joe

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