2000 Mercury Mountaineer

Electrical problem
2000 Mercury Mountaineer V8 Four Wheel Drive Automatic 178000 miles

Hello out there! I am happy to see a forum I can send my problems too with good results. I hear you guys are the best. My question is about my 2000 Mountaineer with a 5.0 engine. I was driving home from work a week ago and suddenly my radio was like being turned on & off by itself. A few seconds later it went off completely. Next at every street light upon stopping at the red ones, I had very little response upon accelelrating. I had to feather the gas pedal in fear of losing power & the engine dieing out. I knew I was losing power to the spark control somewhere. It took me 35 minutes to get home signing of great relief. The trip to my work has its downs from very poor neighborhoods to pass through everyday. It seems when I was able to hook up a battery charger the meter would set at a 12 amp charge for a few minutes, & then completely shut down. I tried that 4 times getting the same results. I hear tell if charging a battery & if you can get the engine running you can hook up a volt meter to it. First in the DC mode and read if 13.5 volts are reading in the idle mode (800 RPMs) & then next switch it to the AC mode to see if a reading shows other than a blank. If a reading shows that will mean a diode is bad causing the backflow in the design of the system correct? Its seems to me bothe the battery & alternator could be bad. It had corrosion on the two battery lugs and the alternator looks very dirty and old, too
Thanks for any help out ther!
August 15, 2009.

Hi there,

You will need to clean all the terminals and bench charge the battery, then get a load test done, this is the only true test for a battery to show its condition, if you can get the alternator bench tested as well, but if that is not possible, with the battery fully charged and in good condition you will be wanting around 13.5 V charge rate with lights and Acc off.

Mark (mhpautos)

Aug 15, 2009.
This is an old one but worth the try.
(Battery or Alternator)?

Loosen one of your battery cables so it can be taken off easily but it will make enough contact to start the engine.
Make sure all the running lights are " OFF" (Headlights, Taillights, etc.) WHY? ≫ If this proves your alternator is o.K. You will blow out the bulbs. Guaranteed < <.
Start the engine and briefly remove the loose battery cable.
If the engine dies out. It is your alternator.
If not and the engine continues to run, it's your battery.
The battery is only needed to start th engine. Once it starts the alternator kicks in and supplies all the needed power to keep the engine running.

I did that little trick years ago and it answered my question of " alternator or battery" every time.
I blew out my headlights and taillights once doing this little trick.

I do have to say 9 times out of 10 it was the battery.

From what you described it seems to me it is your battery.

Although the alternator may look dirty and old, they are sometimes like a " Timex Watch".
It takes a lickin' but keeps on tickin'.

Good Luck; Rick

Nov 12, 2009.
DO NOT REMOVE THE BATTERY CABLE WITH THE ENGINE RUNNING, You will run the risk of damaging the alternator, regulator and the voltage spike may do serious damage to the ECU, Never remove the battery cable with the engine running!

Mark (mhpautos)

Nov 12, 2009.
If you remove your battery cable " briefly" when the engine is running you will not do any damage to any components at all. The key word is " BRIEFLY". Just a few seconds with the battery cable removed will tell you what you want to know without causing any damage to your alternator or regulator. Also, you will not have a voltage spike which may do serious damage to the ECU.

Pull the cable off " BRIEFLY". For one-two seconds. If the engine dies it is your alternator, if not it's your battery.
It only takes 1 -2 seconds for the answer your looking for and put the battery cable right back on.
I have done this many, many times without having any damage to any other components at all.


Nov 13, 2009.
A link that may help with this discussion.

Mark (mhpautos)

Nov 13, 2009.
HHmmmmm. Interesting.
I have been pulling one battery cable off to have the engine die (Alternator Problem) or continue running (Battery Problem) since the early 70's. I was shown that maneuver by an " old" mechanic who was in his sixties back then. I only had one situation where I blew out both headlights because they were on when I pulled the cable off.
I guess I have been pretty lucky through the years.
Oh well, like they say. With automobiles you can learn something " new" now and then!

I appreciate the link for the information Mark.

Ftwpjw - Although I have never had a major damage situation performing what I suggested.I hope you waited and did not pull the battery cable off!
My sincere apologies to you.

I would follow Mark's suggestions or if you have a Advance Auto near your location they will check your battery and alternator free of charge. They also provide a OBD-II Trouble Code Scan free of charge if you ever have trouble with the (CEL) Check Engine Light on.

Take care Mark and good luck ftwpjw with diagnosing your problem with your (Alternator) or (Battery).


Nov 14, 2009.