1993 sport alternator problem?

[bronco351]

I was putting the Explorer in the garage about an hour ago, and it started up fine, but died five seconds later. So I started it again, put it into drive, and drove it forward a few feet and it died before I could even get it into park. It also made a bit of a groan when it killed. It starts up fine, but only runs for 5-10 seconds before it kills again.

The problem started two weeks ago when I got home from work, and the stereo reset itselve for no apparent reason ejecting the CD. I got into the car, and everything seemed okay after that, and I had no problems starting the truck.

Last week when I was at the grocery store and came out to the truck, and it wouldn't start, just clicked, and all of the interior lights were dim. Luckily I had a portable battery jumper with me, and I got the truck started and drove it home. It seemed fine after that, so I figured the battery might just not be holding a good charge anymore.

The truck ran without problems for the next week until today. Monday I bought a 1000 ca 850 cca battery from Wal- Mart and installed it. Car ran fine all day Monday, and yesterday I drove over 90 miles without any problems. So I let the truck sit in the driveway and when I go to start it I have the problem I described the first paragraph.

Now at least it is stuck in the garage where I can work on it, but I still can't drive the Ex until I get it fixed. The voltmeter reads lower than usual when I put the key into the ignition, but I don't believe the factory one is much useful to begin with.

I don't feel like spending money on an alternator if I don't need one, but I am pretty sure that it is the problem. BTW all the belts look fine and were just replaced by a reputable shop in August. Anyone have any advice or know what I should look for?

Thanks in advance for your help.

 

[Opera House]

I doubt the alternator. Engine shutting off sounds like a wiring problem. Your symptoms point is several directions. Good digital volt meters are available for as little as $5. Without one, you might as well throw chicken bones on the hood. Usual suspects: intermitant battery cable just under wire at connector, power distribution takeoff at fender starter solenoid, bad ground between engine and frame, corroded fuse contacts.

 

[bronco351]

I took the alternator out today, so I may as well have it tested since it's already out. I guess it could be a number of electrical issues.

 

[mhn3773]

could it be the pos or neg on the batt? if they are even a tiny bit losse it wont charge the batt i learned that the hard way

 

[bronco351]

No, actually they're on so tight it's difficult to remove them. I checked the voltage on the battery and got 13.1, plenty to start the truck.

 

[Opera House]

General Electrical Diagnostics

To diagnose electrical problems, always have the same reference point. Remove the battery terminal from the negative post. Clean the post and the connector. Then reattach and tighten. This will insure that this one connection is good. All voltage measurements should be made from this electrical terminal.
1. With the engine off, turn on the headlights to create a current load of about 20 amps. Bad connections have resistance and a voltage is developed when a current is passed through them. If headlights do not turn on go to step 3.

2.With headlights on and engine off, measure the voltage from the NEG battery terminal to the vehicle body. This should be some place that does not have a wire going to it. If voltage is greater than 0.25 volts then there is a grounding problem..

NOTE: The negative terminal of the battery is normally connected to the engine block. There may also be a smaller wire that connects to the body. Engines are electrically isolated from the frame and body. There are an additional two to three ground straps that connect the engine to the body and frame. These straps can corrode and break. Then the only connection is through bearings that have higher resistance and can be intermittent. There should be always at least two current paths. When you find one that has failed, there is also another one that has failed. Add that extra ground strap to have reliable operation.

3. Measure the voltage from the NEG battery terminal to the POS center post of the battery and record the voltage. Voltage below 12V indicates a discharged battery. If above 11V you can continue testing. Now measure the voltage on the battery connector. This voltage should be exactly the same.

NOTE: The positive terminal of the battery is normally connected to the starter terminal. There will also be a smaller wire that connects +12 volts to a power distribution point. This will be the starter solenoid (relay) on the fender. Power to the fuse block and output from the alternator connects here. Typical battery voltage with the engine off is 12.5 to 12.8 volts.

4. Measure the voltage from the NEG battery terminal to the stud on power distribution point (solenoid). This voltage should not be lower than 0.1V below that measured at the battery.

5. Measure the voltage from the NEG battery terminal to the main (40A) fuse in the distribution box. This voltage should not be lower than 0.2V below that measured at the battery. Measure this voltage on both sides of the fuse. Check the manual for the correct fuse location. Headlights may be turned off if the problem has been found.

NOTE: Fuses have a holes in the top just over the pins. If the probe will not fit in, use a pin or an awl to make contact. Some fuses have switched power. You will either have a normal 12V or nothing. If you see a voltage in between, there is a wiring problem.

6. Measure the voltage (engine not running) from the NEG battery terminal to the stud output of the alternator. Don't slip with the probe, this terminal can supply a lot of current. This voltage should not be lower than 0.1V below that measured at the battery. If no voltage is present, the fuseable link between the alternator and distribution point has blown .

7. Turn the ignition key on but do not start the vehicle. The battery idiot light should be on. The alternator regulator is turned on through this lamp. If the lamp doesn't light there could be a loose connector on the dash. In the dash there is a resistor across this lamp. In the unlikely event the lamp fails, the alternator will continue to charge. Measured at the alternator plug, the lamp LG/R wire should have greater than 0.2V with the ignition on.

8. Measured at the alternator plug, the regulator 12V power Y/W wire should have the approximate battery voltage. This is powered at all times. If nominal battery voltage is not present, check the 15A regulator fuse in the distribution box.

9. Start the vehicle. Measure the voltage from the NEG battery terminal to the POS terminal of the battery. If the alternator is charging the voltage should be over 13.5 volts. Turn the headlights on and verify the voltage is at least 13.2 volts. Even an alternator with a defective regulator can put out small amounts of current from residual magnetism in the rotor. Voltage of over 14.5 volts indicates an overcharging condition.

 

[bronco351]

Thanks for the post opera house. I will check these things today. Alternator tested out fine when I took it in, so at least I know for certain it isn't that.

 

[bronco351]

Problem fixed

I finally found out what the problem was. It's the a/c compressor. It must have been putting too much strain on the serpentine belt, and the car wouldn't continue running. I unplugged the wiring harness to it, and now I don't have starting problems at all now. But the compressor is shot and I will need a new one before summer.