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View Full Version : Electrical Help diagnose charging system!


Hokie
05-02-2013, 01:06 PM
I'm considering buying a DeLorean. The owner has informed me that the charging system has a problem. They pulled the alternator and had it tested, and the alternator is good. The battery is new. They are not sure what to check next. I gave them a diagram of the relays, circuit breaker and fuses because they said they were going to start there. Any ideas as to what the problem might be and in what order to test components (i.e., check this first, that second, etc.?) Thanks so much!
Chris4099
05-02-2013, 01:28 PM
Chances are it's a bad connection. You'll need to start cleaning grounds (this can have a huge effect on the overall car). Start with the main battery ground to frame connection (be careful and remove the locking nut first as you don't want to snap the bolt). The engine to frame ground would be next. If either of these are bad, it will cause low voltages and charging issues. Also a good idea would be to clean the main positive connections too. This would be at the starter, the alternator and the positive post behind the bulk head connector cover. If they are dirty and this fixed the charging issue, then you probably have plenty of other bad/dirty grounds that should be addressed as well. But the ones mentioned should at least fix the charging system.
Jonathan
05-02-2013, 01:34 PM
The battery light bulb in the instrument cluster... or the belt.

http://dmctalk.org/showthread.php?6988-LED-battery-light
Hokie
05-02-2013, 01:46 PM
The battery light bulb in the instrument cluster... or the belt.

http://dmctalk.org/showthread.php?6988-LED-battery-light

Do I understand correctly that this refers to the battery indicator light?
Chris4099
05-02-2013, 01:58 PM
When the key is to the on ignition position but not running, the battery indicator light (on the right and just below the oil light) should light up. It should also light up when starting the car and then quickly turn off. If you don't see it briefly turn on, then chances are it's either burned out or disconnected from the alternator. The alternator actually relies on that bulb and if it's not working it won't charge the battery correctly. Not common but very quick to confirm if it's good.
Jonathan
05-02-2013, 02:45 PM
Do I understand correctly that this refers to the battery indicator light?

Yes. What Chris said. If it is missing, or failed, or an LED, it doesn't allow the system to work as designed.
Bitsyncmaster
05-02-2013, 05:11 PM
Another common problem is the small wire gets disconnected at the alternator.
Hokie
05-02-2013, 08:36 PM
Chances are it's a bad connection. You'll need to start cleaning grounds (this can have a huge effect on the overall car). Start with the main battery ground to frame connection (be careful and remove the locking nut first as you don't want to snap the bolt). The engine to frame ground would be next. If either of these are bad, it will cause low voltages and charging issues. Also a good idea would be to clean the main positive connections too. This would be at the starter, the alternator and the positive post behind the bulk head connector cover. If they are dirty and this fixed the charging issue, then you probably have plenty of other bad/dirty grounds that should be addressed as well. But the ones mentioned should at least fix the charging system.

I'd like to thank all who have replied. The suggestions to date have been helpful. After following up on each of your suggestions, the owner finds there is still some sort of ground problem, somewhere. Wish I could give them a step by step instruction on what to do next, but I lack the knowledge and have no shop manuals. We'll see what happens! I'll post the results here.
Rich
05-02-2013, 08:49 PM
After following up on each of your suggestions, the owner finds there is still some sort of ground problem, somewhere. Wish I could give them a step by step instruction on what to do next....

For helping the owner find all of the grounds you could point to this: LINK: http://dmctalk.org/showthread.php?1301 (http://dmctalk.org/showthread.php?1301)
Hokie
05-04-2013, 02:42 PM
I'd like to thank all who have replied. The suggestions to date have been helpful. After following up on each of your suggestions, the owner finds there is still some sort of ground problem, somewhere. Wish I could give them a step by step instruction on what to do next, but I lack the knowledge and have no shop manuals. We'll see what happens! I'll post the results here.

It was the voltage regulator in the alternator all along! Problem solved, but alas, I did not buy the car. Same old story, for sale by a "dealer" (not a DMC dealer) that doesn't know what they have, and want way too much for it. So, the dream continues. The Lord works in mysterious ways, we'll wait and see what He has in store.