Weird electrical problem

[Wyostang]

Ok, so I am having a very odd electrical system issue. I have a 1972 coupe 351c 2v. I put a new battery in it after I bought it off a mechanic who had done some good engine work on it. It was having some trouble starting after I first got it so I thought, no problem, needs a battery. It ran great for about 2 days and then wouldn't start without a jump. So I thought, alternator, no problem took it our had it checked...it was good to go. Started to get a little worried, cleaned all the terminals for the battery and connections for the alternator. Charged the battery off of my truck. Started it up tonight and drove it around and then...the blinkers stopped working, the dash lights went out and then the headlights. The car was still running still and I noticed when I pulled the headlight switch in and out I heard a surging noise. What could be draining on the battery? Bad grounding? Do you guys think it could be a bad cable or wire? Do I need a new regulator? New wiring harness? I have some serious electrical gremlins going on and it is disrupting my Mustang cruising fun.

 

[rvrtrash]

I hope you have a good voltmeter, because you need to do some checks. Charge the battery with the cables disconnected. Check the voltage. Hook the cables up. Check the voltage again. Should be the same. What is the voltage when it's running and all accessories off? What is the voltage at the rear of the alternator? This info will start to point you in the correct direction.

Steve

 

[midlife]

Sounds like you have a pretty good current draw when the car is off. Here's my trouble-shooting guide to shorts:

When ready to check out the harness, close all doors, turn off all lights, ignition key in the OFF position, accessories off, etc. Make sure both battery connectors are disconnected. Connect the positive battery cable to the starter solenoid. Leave the negative terminal disconnected from the battery. Then use a digital volt meter to measure the current draw across the battery. Place one probe of the DVM on the negative battery cable terminal, and the other probe on the negative battery post. Be sure that the DVM is set to amps, DC. If there are no shorts in the wiring connections, the reading should be on the order of 30 milliamps or less. Anything above 1 amp indicates some accessory is on; readings above 10 amps (may blow the fuse on the DVM) indicates a dead short.

If you have a short, disconnect all other wiring from the starter solenoid post where the battery connects and re-measure the current. If current drops, the source is the underdash wiring harness or the harness from the starter solenoid to the firewall. Reconnect the wiring to the starter post and then disconnect the underhood harness from the firewall and test again to isolate the source of the short.

If the short is not in the underhood or underdash harness, the problem lies in the alternator or voltage regulator. Disconnect each of these in turn to isolate the source.

If the short or high current comes from the underdash region, keep the battery negative side disconnected and remove one fuse at a time. Measure the current as above. If you now see low current, there is either a short or an item on that particular fuse circuit is on. Turn off that item and continue checking.

Eventually, you’ll have low current readings with all fuses installed and all wiring connected. This series of tests checks all of the battery directly powered systems. To check the Accessory systems, now repeat all of the tests above with the ignition key in the ACC position. The current with the key in the ACC position may be up to 1 amp or so. When all of the tests are done and no anomalous current is noted, at that time, and only at that time, is it safe to connect the negative battery cable to the battery.

 

[wwhite72]

I had a 72 bronco that stopped dead on the side of the road due to a bad ground on the cigarette lighter. Darndest thing. A few guys here can probably tell you how to check the resistance in your headlight switch and how to clean all the contacts. I just replace the switches with real Ford parts whenever possible. Or repos from dealers that have tested them. Arent expensive.

 

[Wyostang]

Fixed! Dang! You guys are a truly a valuable resource, see, this is why it is great to be a member of this forum. As it turns out it was a fuseable link. Everything is running strong now and as an aded bonus my dash panel is much better lit than previously. Thanks a lot for all the help. Now here is my next question my LH interior blinker indicator is gone how can I get to that?