Tontate

I've been struggling with my car not starting and/or dying while driving on the road. I bought a new battery thinking it's the cheapest first step and things went well for a while. But then the problem reemerged. I took it into a shop and swapped out the alternator for a rebuilt one. Things were good for a month and then the problem started again. For the next few little while I thought I would simply just unplug the batter whenever I don't drive it. But then one day the car just died on the road. I took the car in to have the alternator tested and also took the battery out to get tested and both appear to be in working order. The mechanic was frustrated and told me he's not an electrician and I'm probably suffering from some sort of intermittent leak. Sometimes the car works well by unplugging the batter and then once in a while it will drop from a full charge to nothing while driving. It's getting so bad I'm seriously thinking of dumping the car. Any ideas as to what could be causing this leak or intermittent short? Anyone? The Car is an 85 5000CD Turbo.

Tontate

btw.. I've recently posted about a bad heater cable servo motor which clicks all the time. Could this have any affect on the electrical system?

Will Ng

that servo motor only runs when the ignition is on.

RussB

If it were me, I'd remove the Bosch voltage regulator / brush assembly from the rear of the alternator (two flat head screws) and examine the brushes. They'll wear down to little nubs. Fortunately the assembly is cheap and is the item that fails most frequently on the alternator.

If you're less lucky, one or more of the rectifier diodes within the alternator has failed and/or the alternator has a shorted turn (less likely still). A local alternator shop will test for you.

Rebuilt 90 Amp alternators are only about $100. Or you could have yours rebuilt locally and should last you another 100,000 miles.

I upgraded my TQ from a 90 Amp alternator to a Bosch rebuilt 110 Amp alternator and it was the best upgrade I've done.

Are you aware that these cars have a splice between the battery and alternator? It's beneath the passemger footwell. I've never had a problem with it, but others have.

Will Ng

First of all, a car's charging system depends on both the alternator and battery to be healthy at the same time. To use a morbid example, they are like siamesed twins. If one is failing, the other can't sustain both. If one dies, the remaining one will soon follow.

Verify that your battery is in fact good. Remove it and have it trickle charged to top it off. Use a voltmeter to check that the battery reads 13.3V.
If it drops past 12V, or the battery draws more than 1A after 6-8 hours of charging, I'd suspect there could be a weak cell.

If the battery is OK, time to move onto the car.

Install the battery and turn the key to IGN position, verify the ALT dash light is illuminated. If not, the alternator regulation circuit is open.

If dash light is OK...Start the car. Let it run for 5 minutes. Now take the voltmeter and check the voltage across the battery terminals. Next, take the voltmeter and check voltage across the underhood charging post and a good chassis ground.
Compare these two readings, there should be no more than 0.25V difference.
If there is a 1V or greater drop at the battery terminals, then the cable splice is corroded.
Also, the reading should be in the neighborhood of 13.3-14.0V
If not, the alternator is defective.

Next, turn on headlights and climate control. Take another voltage reading at the battery terminals.
If the reading dips to 12V or below, the alternator isn't regulating voltage well.
It should be at least 12.8V.

Next, we test for drain issues. Shut off the engine, and remove the battery ground strap. Configure the multimeter to ammeter mode to measure current flow. Most have two settings...1A or less, and 10A. Set it to the lower setting. Place the ammeter in between the ground strap and the negative battery terminal. Whatever level of current drain will register on the meter. You should get a reading of less than 100ma for a normal car. If you see a larger reading, begin pulling the car fuses one by one to discover which circuit contains the culprit.

If the drain test is OK, next move under the hood and begin inspecting the chassis grounds. Make sure they exist, and not impeded by corrosion. There should be one from the firewall to the cylinder head, and one thick one from the driver-side engine mount area to the engine block.

Note, you mentioned the car just died while driving....suddenly shutting off, or sputtering, with dashboard lights blinking wildly before shutdown? Was the battery depleted? The second scenerio is indicative of a depleted battery.

boxerfan

Well said Will

audiqv8

Agree!!!!! Well said Will

Will Ng

thanx guys!

Tontate

Thanks Will, I do have a multimeter and will do as you suggested and as for the sputtering that is exactly what happened. I always thought that the alternator would keep the car going if the battery was depleted. I'll run those tests and post back with my results. The night the car died on the road I had forgotten to unplug the battery cable from the terminal (as I am used to doing) so it probably drained low yet remained charged enough to start the car and get me on the road.

Tontate

Will, I went down the list of troubleshooting tips and as soon as I started testing for amp draw I noticed that the car was drawing 1.6 amps while turned off. I started pulling out fuses until I reached the door lock/mirror fuse(10). When I pulled that sucker out the amps dropped back down to less than 100ma.

I went for a drive with the heat, radio and lights on and when I returned the battery seemed perfectly healthy.. I hope this is it...

Thanks for the help!